LMK04906 LMK04906
10 GbE
PHY 10 GbE
PHY FPGA NPU SONET SONET
622.08,
155.52, 77.76,
19.44 MHz
Hitless Switching, Jitter
Cleaning, Frequency
Multiplication, and
Programmable Clock
Distribution
Backplane
156.25 MHz
LVPECL 100 MHz
LVDS
33.33 MHz
LVCMOS
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Recovered
³GLUW\´FORFNV
or clean clocks
0XOWLSOH³FOHDQ´
clocks at different
frequencies
CLKout2
CLKout3
CLKout0
FPGA
CLKin0
Crystal or
VCXO
Backup
Reference
Clock
CLKin1
OSCout0
CLKout4 DAC
ADC
LMX2541
PLL+VCO Serializer/
Deserializer
LMK04906
Precision Clock
Conditioner
CLKout1
CLKin2
CPLD
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An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LMK04906
SNAS589F JUNE 2012REVISED AUGUST 2017
LMK04906 Ultralow Noise Clock Jitter Cleaner and Multiplier With
6 Programmable Outputs
1
1 Features
1 Ultralow RMS Jitter Performance
100-fs RMS Jitter (12 kHz to 20 MHz)
123-fs RMS Jitter (100 Hz to 20 MHz)
Dual Loop PLLatinum™ PLL Architecture
PLL1
Integrated Low-Noise Crystal Oscillator
Circuit
Holdover Mode when Input Clocks are Lost
Automatic or Manual
Triggering/Recovery
PLL2
Normalized [1 Hz] PLL Noise Floor of –227
dBc/Hz
Phase Detector Rate up to 155 MHz
OSCin Frequency-doubler
Integrated Low-Noise VCO
3 Redundant Input Clocks with LOS
Automatic and Manual Switch-Over Modes
50% Duty Cycle Output Divides, 1 to 1045 (Even
and Odd)
LVPECL, LVDS, or LVCMOS Programmable
Outputs
Precision Digital Delay, Fixed or Dynamically
Adjustable
25-ps Step Analog Delay Control.
6 Differential Outputs. Up to 12 Single Ended.
Up to 5 VCXO/Crystal Buffered Outputs
Clock Rates of up to 2600 MHz
0-Delay Mode
Three Default Clock Outputs at Power Up
Multi-mode: Dual PLL, Single PLL, and Clock
Distribution
Industrial Temperature Range: –40 to 85 °C
3.15-V to 3.45-V Operation
Package: 64-Pin WQFN (9 mm × 9 mm × 0.8 mm)
2 Applications
10G, 40G, and 100G OTN Line Cards
SONET/SDH OC-48/STM-16 and OC-192/STM-
64 Line Cards
GbE/10GbE, 1/2/4/8/10GFC Line Cards
ITU G.709 and Custom FEC Line Cards
Synchronous Ethernet
Optical Modules
DSLAM/MSANs
Test and Measurement
Broadcast Video
Wireless Basestations
Data Converter Clocking
Microwave ODU and IDUs for Wireless Backhaul
3 Description
The LMK04906 is the industry's highest performance
clock jitter attenuator with superior clock jitter
cleaning, generation, and distribution with advanced
features to meet high performance timing application
needs.
The LMK04906 accepts 3 clock inputs ranging from 1
kHz to 500 MHz and generates 6 unique clock output
frequencies ranging from 284 kHz to 2.6 GHz. The
LMK04906 can also buffer a crystal or VCXO to
generate a 7th unique clock frequency.
The device provides virtually all frequency translation
combinations required for SONET, Ethernet, Fibre
Channel and multi-mode Wireless Base Stations.
The LMK04906 input clock frequency and clock
multiplication ratio are programmable through a SPI
interface.
Device Information(1)
PART NUMBER VCO FREQUENCY REFERENCE
INPUTS
LMK04906 2370 to 2600 MHz 3
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
System Application Diagram Simplified LMK04906 Block Diagram
2
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Table of Contents
1 Features.................................................................. 1
2 Applications ........................................................... 1
3 Description............................................................. 1
4 Revision History..................................................... 2
5 Pin Configuration and Functions......................... 3
6 Specifications......................................................... 5
6.1 Absolute Maximum Ratings ..................................... 5
6.2 ESD Ratings.............................................................. 5
6.3 Recommended Operating Conditions ...................... 5
6.4 Thermal Information.................................................. 5
6.5 Electrical Characteristics........................................... 6
6.6 Timing Requirements.............................................. 12
6.7 Typical Characteristics............................................ 13
7 Parameter Measurement Information ................ 14
7.1 Charge Pump Current Specification Definitions...... 14
7.2 Differential Voltage Measurement Terminology...... 15
8 Detailed Description............................................ 17
8.1 Overview................................................................. 17
8.2 Functional Block Diagram....................................... 21
8.3 Feature Description................................................. 21
8.4 Device Functional Modes........................................ 42
8.5 Programming........................................................... 45
8.6 Register Maps......................................................... 48
9 Application and Implementation ........................ 85
9.1 Application Information............................................ 85
9.2 Typical Application ............................................... 101
9.3 System Examples ................................................. 108
9.4 Do's and Don'ts..................................................... 111
10 Power Supply Recommendations ................... 112
10.1 Pin Connection Recommendations..................... 112
10.2 Current Consumption and Power Dissipation
Calculations............................................................ 113
11 Layout................................................................. 115
11.1 Layout Guidelines ............................................... 115
11.2 Layout Example .................................................. 117
12 Device and Documentation Support............... 118
12.1 Device Support.................................................... 118
12.2 Receiving Notification of Documentation
Updates.................................................................. 118
12.3 Community Resource.......................................... 118
12.4 Trademarks......................................................... 118
12.5 Electrostatic Discharge Caution.......................... 118
12.6 Glossary.............................................................. 118
13 Mechanical, Packaging, and Orderable
Information......................................................... 118
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision E (August 2016) to Revision F Page
Changed From: CLKout3_PD = 0 To: CLKout2_PD = 0 in Table 7..................................................................................... 37
Changed From: CLKout3_PD = 0 To: CLKout2_PD = 0 in Table 9..................................................................................... 40
Changes from Revision D (May 2013) to Revision E Page
Changed 750 to 500............................................................................................................................................................... 1
Changed 2.26 MHz to 284 kHz.............................................................................................................................................. 1
Added ESD Ratings table, Feature Description section, Device Functional Modes,Application and Implementation
section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and
Mechanical, Packaging, and Orderable Information section ................................................................................................. 1
Changed Clock Switch Event With Holdover section........................................................................................................... 26
Deleted Clock Switch Event without Holdover section......................................................................................................... 26
Changed 5 cycles to 5.5 cycles............................................................................................................................................ 38
Changed 5 cycles to 5.5 cycles............................................................................................................................................ 41
Added (Auto modes only)..................................................................................................................................................... 70
Changed equation ................................................................................................................................................................ 94
Changes from Revision C (May 2013) to Revision D Page
Changed layout of National Semiconductor Data Sheet to TI format. ............................................................................... 115
6364 62 61 60 59 58 57 56 55 54 53
CLKout4
NC
CLKout5*
Status_CLKin0
CLKout4*
NC
Vcc12
CLKout5
NC
NC
Status_CLKin1
Vcc13
DAP
52 51 50 49
CLKout3
Vcc11
CLKout3*
NC
CLKin2*
NC
NC
Vcc3
Vcc4
NC
CLKout2*
CLKout2
GND
FBCLKin/Fin/CLKin1
FBCLKin*/Fin*/CLKin1*
Status_Holdover
CLKin0
CLKin0*
Vcc5
CLKin2
38
37
39
40
41
42
43
44
45
46
47
48
Vcc7
CPout2
Vcc9
CLKuWire
OSCin*
OSCout0
OSCout0*
Vcc8
LEuWire
DATAuWire
Vcc10
NC
34
33
35
36
CPout1
Status_LD
Vcc6
OSCin
Vcc2
11
12
10
9
8
7
6
5
4
3
2
1
NC
CLKout0*
NC
CLKout0
NC
SYNC/
Status_CLKin2
NC
NC
Vcc1
LDObyp1
LDObyp2
15
16
14
13CLKout1
CLKout1*
NC
1817 19 20 21 22 23 24 25 26 27 28 29 30 31 32
NC
3
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(1) See Application and Implementation section for recommended connections.
5 Pin Configuration and Functions
NKD Package
64-Pin WQFN With Exposed Pad
Top View
Pin Functions
PIN I/O TYPE DESCRIPTION(1)
NAME NO.
Vcc13 1 PWR Power Supply for CLKou0
NC
2, 5, 7, 8, 9, 15,
17, 19
22, 47, 51, 55,
56, 60,
61, 64
No Connect These pins must be left floating.
CLKout0*, CLKout0 3, 4 O Programmable Clock output 0.
SYNC /
Status_CLKin2 6 I/O Programmable CLKout Synchronization input or CLKin2 Status output.
Vcc1 10 PWR Power supply for VCO LDO.
LDObyp1 11 ANLG LDO Bypass, bypassed to ground with 10 µF capacitor.
4
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Pin Functions (continued)
PIN I/O TYPE DESCRIPTION(1)
NAME NO.
LDObyp2 12 ANLG LDO Bypass, bypassed to ground with a 0.1 µF capacitor.
CLKout1, CLKout1* 13, 14 O Programmable Clock output 1.
Vcc2 16 PWR Power supply for CLKout1.
Vcc3 18 PWR Power supply for CLKout2
CLKout2*, CLKout2 20, 21 O Programmable Clock output 2
GND 23 PWR Ground
Vcc4 24 PWR Power supply for digital.
CLKin1, CLKin1*
25, 26 I ANLG
Reference Clock Input Port 1 for PLL1. AC or DC Coupled.
FBCLKin, FBCLKin* Feedback input for external clock feedback input (0-delay mode).
AC or DC Coupled.
Fin/Fin* External VCO input (External VCO mode). AC or DC Coupled.
Status_Holdover 27 I/O Programmable Programmable status pin, default readback output. Programmable
to holdover mode indicator. Other options available by
programming.
CLKin0, CLKin0* 28, 29 I ANLG Reference Clock Input Port 0 for PLL1.
AC or DC Coupled.
Vcc5 30 PWR Power supply for clock inputs.
CLKin2, CLKin2* 31, 32 I ANLG Reference Clock Input Port 2 for PLL1,
AC or DC Coupled.
Status_LD 33 I/O Programmable Programmable status pin, default lock detect for PLL1 and PLL2.
Other options available by programming.
CPout1 34 O ANLG Charge pump 1 output.
Vcc6 35 PWR Power supply for PLL1, charge pump 1.
OSCin, OSCin* 36, 37 I ANLG Feedback to PLL1, Reference input to PLL2.
AC Coupled.
Vcc7 38 PWR Power supply for OSCin port.
OSCout0, OSCout0* 39, 40 O Programmable Buffered output 0 of OSCin port.
Vcc8 41 PWR Power supply for PLL2, charge pump 2.
CPout2 42 O ANLG Charge pump 2 output.
Vcc9 43 PWR Power supply for PLL2.
LEuWire 44 I CMOS MICROWIRE Latch Enable Input.
CLKuWire 45 I CMOS MICROWIRE Clock Input.
DATAuWire 46 I CMOS MICROWIRE Data Input.
Vcc10 48 PWR Power supply for CLKout3.
CLKout3, CLKout3* 49, 50 O Programmable Clock output 3.
Vcc11 52 PWR Power supply for CLKout4.
CLKout4, CLKout4* 53, 54 O Programmable Clock output 4.
Vcc12 57 PWR Power supply for CLKout5.
CLKout5, CLKout5* 58, 59 O Programmable Clock output 5.
Status_CLKin0 62 I/O Programmable Programmable status pin. Default is input for pin control of PLL1
reference clock selection. CLKin0 LOS status and other options
available by programming.
Status_CLKin1 63 I/O Programmable Programmable status pin. Default is input for pin control of PLL1
reference clock selection. CLKin1 LOS status and other options
available by programming.
DAP DAP GND DIE ATTACH PAD, connect to GND.
5
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(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
(3) Never to exceed 3.6 V.
6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)(1)(2)
MIN MAX UNIT
VCC Supply voltage (3) –0.3 3.6 V
VIN Input voltage –0.3 (VCC + 0.3) V
IIN Differential input current (CLKinX/X*,
OSCin/OSCin*, FBCLKin/FBCLKin*, Fin/Fin*) ±5 mA
MSL Moisture sensitivity level 3
TJJunction temperature 150 °C
Tstg Storage temperature –65 150 °C
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
(2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
6.2 ESD Ratings VALUE UNIT
V(ESD) Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) ±2000
V
Charged-device model (CDM), per JEDEC specification JESD22-
C101(2) ±750
Machine model (MM) ±150
6.3 Recommended Operating Conditions MIN NOM MAX UNIT
TJJunction temperature 125 °C
TAAmbient temperature VCC = 3.3 V –40 25 85 °C
VCC Supply voltage 3.15 3.3 3.45 V
(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report.
6.4 Thermal Information
THERMAL METRIC(1) LMK04906
UNITNKD (WQFN)
64 PINS
RθJA Junction-to-ambient thermal resistance 25.2 °C/W
RθJC(top) Junction-to-case (top) thermal resistance 6.9 °C/W
RθJB Junction-to-board thermal resistance 4 °C/W
ψJT Junction-to-top characterization parameter 0.1 °C/W
ψJB Junction-to-board characterization parameter 4 °C/W
RθJC(bot) Junction-to-case (bottom) thermal resistance 0.8 °C/W
6
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(1) Load conditions for output clocks: LVDS: 100 Ωdifferential. See Current Consumption and Power Dissipation Calculations for ICC for
specific part configuration and how to calculate ICC for a specific design.
(2) CLKin0, CLKin1, and CLKin2 maximum is specified by characterization, production tested at 200 MHz.
(3) Specified by characterization.
(4) See Differential Voltage Measurement Terminology for definition of VID and VOD voltages.
6.5 Electrical Characteristics
(3.15 V VCC 3.45 V, -40 °C TA85 °C. Typical values represent most likely parametric norms at VCC = 3.3 V, TA= 25
°C, at the Recommended Operating Conditions at the time of product characterization and are not ensured.)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
CURRENT CONSUMPTION
ICC_PD Power Down Supply Current 1 3 mA
ICC_CLKS Supply Current with all clocks enabled
(1)
All clock delays disabled,
CLKoutX_DIV = 1045,
CLKoutX_TYPE = 1 (LVDS),
PLL1 and PLL2 locked. 410 470 mA
CLKin0/0*, CLKin1/1*, and CLKin2/2* INPUT CLOCK SPECIFICATIONS
fCLKin Clock Input Frequency
(2) 0.001 500 MHz
SLEWCLKin Clock Input Slew Rate
(3) 20% to 80% 0.15 0.5 V/ns
VIDCLKin Clock Input
Differential Input Voltage
(4)
Figure 4
AC coupled
CLKinX_BUF_TYPE = 0 (Bipolar) 0.25 1.55 |V|
VSSCLKin 0.5 3.1 Vpp
VIDCLKin AC coupled
CLKinX_BUF_TYPE = 1 (MOS) 0.25 1.55 |V|
VSSCLKin 0.5 3.1 Vpp
VCLKin Clock Input
Single-ended Input Voltage
(3)
AC coupled to CLKinX; CLKinX* AC
coupled to Ground
CLKinX_BUF_TYPE = 0 (Bipolar) 0.25 2.4 Vpp
AC coupled to CLKinX; CLKinX* AC
coupled to Ground
CLKinX_BUF_TYPE = 1 (MOS) 0.25 2.4 Vpp
VCLKin0-offset DC offset voltage between
CLKin0/CLKin0*
CLKin0* - CLKin0
Each pin AC coupled
CLKin0_BUF_TYPE = 0 (Bipolar)
20 mV
VCLKin1-offset DC offset voltage between
CLKin1/CLKin1*
CLKin1* - CLKin1 0 mV
VCLKin2-offset DC offset voltage between
CLKin2/CLKin2*
CLKin2* - CLKin2 20 mV
VCLKinX-offset DC offset voltage between
CLKinX/CLKinX*
CLKinX* - CLKinX Each pin AC coupled
CLKinX_BUF_TYPE = 1 (MOS) 55 mV
VCLKin- VIH High input voltage DC coupled to CLKinX; CLKinX* AC
coupled to Ground
CLKinX_BUF_TYPE = 1 (MOS)
2 VCC V
VCLKin- VIL Low input voltage 0 0.4 V
FBCLKin/FBCLKin* and Fin/Fin* INPUT SPECIFICATIONS
fFBCLKin Clock Input Frequency
(3) AC coupled
(CLKinX_BUF_TYPE = 0)
MODE = 2 or 8; FEEDBACK_MUX = 6 0.001 1000 MHz
fFin Clock Input Frequency
(3) AC coupled
(CLKinX_BUF_TYPE = 0)
MODE = 3 or 11 0.001 3100 MHz
VFBCLKin/Fin Single Ended
Clock Input Voltage
(3) AC coupled;
(CLKinX_BUF_TYPE = 0) 0.25 2 Vpp
SLEWFBCLKin/Fin Slew Rate on CLKin
(3) AC coupled; 20% to 80%;
(CLKinX_BUF_TYPE = 0) 0.15 0.5 V/ns
7
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Electrical Characteristics (continued)
(3.15 V VCC 3.45 V, -40 °C TA85 °C. Typical values represent most likely parametric norms at VCC = 3.3 V, TA= 25
°C, at the Recommended Operating Conditions at the time of product characterization and are not ensured.)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
(5) This parameter is programmable
(6) FOSCin maximum frequency specified by characterization. Production tested at 200 MHz.
(7) See Optional Crystal Oscillator Implementation (OSCin/OSCin*)
PLL1 SPECIFICATIONS
fPD1 PLL1 Phase Detector Frequency 40 MHz
ICPout1SOURCE PLL1 Charge
Pump Source Current
(5)
VCPout1 = VCC/2, PLL1_CP_GAIN = 0 100
µA
VCPout1 = VCC/2, PLL1_CP_GAIN = 1 200
VCPout1 = VCC/2, PLL1_CP_GAIN = 2 400
VCPout1 = VCC/2, PLL1_CP_GAIN = 3 1600
ICPout1SINK PLL1 Charge
Pump Sink Current
(5)
VCPout1=VCC/2, PLL1_CP_GAIN = 0 –100
µA
VCPout1=VCC/2, PLL1_CP_GAIN = 1 –200
VCPout1=VCC/2, PLL1_CP_GAIN = 2 –400
VCPout1=VCC/2, PLL1_CP_GAIN = 3 –1600
ICPout1%MIS Charge Pump
Sink / Source Mismatch VCPout1 = VCC/2, T = 25 °C 3% 10
ICPout1VTUNE Magnitude of Charge Pump Current
Variation vs. Charge Pump Voltage 0.5 V < VCPout1 < VCC - 0.5 V
TA= 25 °C 4%
ICPout1%TEMP Charge Pump Current vs. Temperature
Variation 4%
ICPout1 TRI Charge Pump TRI-STATELeakage
Current 0.5 V < VCPout < VCC - 0.5 V 5 nA
PN10kHz PLL 1/f Noise at 10-kHz offset.
Normalized to 1-GHz Output
Frequency
PLL1_CP_GAIN = 400 µA –117 dBc/Hz
PLL1_CP_GAIN = 1600 µA –118
PN1Hz Normalized Phase Noise Contribution PLL1_CP_GAIN = 400 µA –221.5 dBc/Hz
PLL1_CP_GAIN = 1600 µA –223
PLL2 REFERENCE INPUT (OSCin) SPECIFICATIONS
fOSCin PLL2 Reference Input
(6) 500 MHz
SLEWOSCin PLL2 Reference Clock minimum slew
rate on OSCin(3) 20% to 80% 0.15 0.5 V/ns
VOSCin Input Voltage for OSCin or OSCin*
(3) AC coupled; Single-ended (Unused pin
AC coupled to GND) 0.2 2.4 Vpp
VIDOSCin Differential voltage swing
Figure 4 AC coupled 0.2 1.55 |V|
VSSOSCin 0.4 3.1 Vpp
VOSCin-offset DC offset voltage between
OSCin/OSCin*
OSCinX* - OSCinX Each pin AC coupled 20 mV
fdoubler_max Doubler input frequency (3) EN_PLL2_REF_2X = 1;
OSCin Duty Cycle 40% to 60% 155 MHz
CRYSTAL OSCILLATOR MODE SPECIFICATIONS
fXTAL Crystal frequency range
(3) RESR < 40 Ω6 20.5 MHz
PXTAL Crystal power dissipation (7) Vectron VXB1 crystal, 20.48 MHz,
RESR < 40 Ω
XTAL_LVL = 0 100 µW
CIN Input capacitance of LMK04906 OSCin
port –40 to +85 °C 6 pF
8
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Electrical Characteristics (continued)
(3.15 V VCC 3.45 V, -40 °C TA85 °C. Typical values represent most likely parametric norms at VCC = 3.3 V, TA= 25
°C, at the Recommended Operating Conditions at the time of product characterization and are not ensured.)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
(8) A specification in modeling PLL in-band phase noise is the 1/f flicker noise, LPLL_flicker(f), which is dominant close to the carrier. Flicker
noise has a 10 dB/decade slope. PN10kHz is normalized to a 10 kHz offset and a 1 GHz carrier frequency. PN10kHz = LPLL_flicker(10
kHz) - 20log(Fout / 1 GHz), where LPLL_flicker(f) is the single side band phase noise of only the flicker noise's contribution to total noise,
L(f). To measure LPLL_flicker(f) it is important to be on the 10 dB/decade slope close to the carrier. A high compare frequency and a clean
crystal are important to isolating this noise source from the total phase noise, L(f). LPLL_flicker(f) can be masked by the reference
oscillator performance if a low power or noisy source is used. The total PLL in-band phase noise performance is the sum of LPLL_flicker(f)
and LPLL_flat(f).
(9) A specification modeling PLL in-band phase noise. The normalized phase noise contribution of the PLL, LPLL_flat(f), is defined as:
PN1HZ=LPLL_flat(f) - 20log(N) - 10log(fPDX). LPLL_flat(f) is the single side band phase noise measured at an offset frequency, f, in a 1 Hz
bandwidth and fPDX is the phase detector frequency of the synthesizer. LPLL_flat(f) contributes to the total noise, L(f).
(10) Maximum Allowable Temperature Drift for Continuous Lock is how far the temperature can drift in either direction from the value it was
at the time that the R30 register was last programmed, and still have the part stay in lock. The action of programming the R30 register,
even to the same value, activates a frequency calibration routine. This implies the part will work over the entire frequency range, but if
the temperature drifts more than the maximum allowable drift for continuous lock, then it will be necessary to reload the R30 register to
ensure it stays in lock. Regardless of what temperature the part was initially programmed at, the temperature can never drift outside the
frequency range of -40 °C to 85 °C without violating specifications.
PLL2 PHASE DETECTOR AND CHARGE PUMP SPECIFICATIONS
fPD2 Phase detector frequency 155 MHz
ICPoutSOURCE PLL2 charge pump source current (5)
VCPout2=VCC/2, PLL2_CP_GAIN = 0 100
µA
VCPout2=VCC/2, PLL2_CP_GAIN = 1 400
VCPout2=VCC/2, PLL2_CP_GAIN = 2 1600
VCPout2=VCC/2, PLL2_CP_GAIN = 3 3200
ICPoutSINK PLL2 charge pump sink current (5)
VCPout2=VCC/2, PLL2_CP_GAIN = 0 –100
µA
VCPout2=VCC/2, PLL2_CP_GAIN = 1 –400
VCPout2=VCC/2, PLL2_CP_GAIN = 2 –1600
VCPout2=VCC/2, PLL2_CP_GAIN = 3 –3200
ICPout2%MIS Charge pump sink/source mismatch VCPout2=VCC/2, TA= 25 °C 3% 10%
ICPout2VTUNE Magnitude of charge pump current vs
charge pump voltage variation 0.5 V < VCPout2 < VCC - 0.5 V
TA= 25 °C 4%
ICPout2%TEMP Charge pump current vs temperature
variation 4%
ICPout2TRI Charge pump leakage 0.5 V < VCPout2 < VCC 0.5 V 10 nA
PN10kHz PLL 1/f noise at 10-kHz offset
(8). Normalized to
1-GHz output frequency
PLL2_CP_GAIN = 400 µA –118 dBc/Hz
PLL2_CP_GAIN = 3200 µA –121
PN1Hz Normalized phase noise contribution (9) PLL2_CP_GAIN = 400 µA –222.5 dBc/Hz
PLL2_CP_GAIN = 3200 µA –227
INTERNAL VCO SPECIFICATIONS
fVCO VCO tuning range LMK04906 2370 2600 MHz
KVCO
Fine tuning sensitivity
(The range displayed in the typical
column indicates the lower sensitivity is
typical at the lower end of the tuning
range, and the higher tuning sensitivity
is typical at the higher end of the tuning
range).
LMK04906 16 to 21 MHz/V
|ΔTCL|Allowable temperature drift for
continuous lock
(10) (3)
After programming R30 for lock, no
changes to output configuration are
permitted to guarantee continuous lock 125 °C
9
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Electrical Characteristics (continued)
(3.15 V VCC 3.45 V, -40 °C TA85 °C. Typical values represent most likely parametric norms at VCC = 3.3 V, TA= 25
°C, at the Recommended Operating Conditions at the time of product characterization and are not ensured.)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
(11) VCXO used is a 122.88 MHz Crystek CVHD-950-122.880.
(12) fVCO = 2457.6 MHz, PLL1 parameters: EN_PLL2_REF_2X = 1, PLL2_R = 2, FPD1 = 1.024 MHz, ICP1 = 100 μA, loop bandwidth = 10 Hz.
A 122.88 MHz Crystek CVHD-950–122.880. PLL2 parameters: PLL2_R = 1, FPD2 = 122.88 MHz, ICP2 = 3200 μA, C1 = 47 pF, C2 = 3.9
nF, R2 = 620 , PLL2_C3_LF = 0, PLL2_R3_LF = 0, PLL2_C4_LF = 0, PLL2_R4_LF = 0, CLKoutX_DIV = 10, and
CLKoutX_ADLY_SEL = 0.
(13) Crystal used is a 20.48 MHz Vectron VXB1-1150-20M480 and Skyworks varactor diode, SMV-1249-074LF.
(14) CLKout3 and OSCout0 also oscillate at start-up at the frequency of the VCXO attached to OSCin port.
(15) Equal loading and identical clock output configuration on each clock output is required for specification to be valid. Specification not valid
for delay mode.
CLKout CLOSED LOOP JITTER SPECIFICATIONS USING A COMMERCIAL QUALITY VCXO (11)
L(f)CLKout
LMK04906
fCLKout = 245.76 MHz
SSB phase noise
Measured at clock outputs
Value is average for all output types
(12)
Offset = 1 kHz –122.5
dBc/Hz
Offset = 10 kHz –132.9
Offset = 100 kHz –135.2
Offset = 800 kHz –143.9
Offset = 10 MHz; LVDS –156
Offset = 10 MHz; LVPECL 1600 mVpp –157.5
Offset = 10 MHz; LVCMOS –157.1
JCLKout
LVDS/LVPECL/
LVCMOS LMK04906(12)
fCLKout = 245.76 MHz
Integrated RMS jitter
BW = 12 kHz to 20 MHz 115 fs rms
BW = 100 Hz to 20 MHz 123
CLKout CLOSED LOOP JITTER SPECIFICATIONS USING THE INTEGRATED LOW NOISE CRYSTAL OSCILLATOR CIRCUIT (13)
LMK04906
fCLKout = 245.76 MHz
Integrated RMS jitter
BW = 12 kHz to 20 MHz
XTAL_LVL = 3 192
BW = 100 Hz to 20 MHz
XTAL_LVL = 3 450
DEFAULT POWER ON RESET CLOCK OUTPUT FREQUENCY
fCLKout-startup Default output clock frequency at
device power on
(14) CLKout4, LVDS, LMK04906 90 98 110 MHz
CLOCK SKEW AND DELAY
|TSKEW|
Maximum CLKoutX to CLKoutY
(15) (3)
LVDS-to-LVDS, T = 25 °C,
FCLK = 800 MHz, RL= 100 Ω
AC coupled 30
ps
LVPECL-to-LVPECL,
T = 25 °C,
FCLK = 800 MHz, RL= 100 Ω
emitter resistors =
240 Ωto GND
AC coupled
30
Maximum skew between any two
LVCMOS outputs, same CLKout or
different CLKout (15) (3)
RL= 50 Ω, CL= 5 pF,
T = 25 °C, FCLK = 100 MHz.
(15) 100
MixedTSKEW LVDS or LVPECL to LVCMOS Same device, T = 25 °C,
250 MHz 750 ps
td0-DELAY CLKin to CLKoutX delay
(15)
MODE = 2
PLL1_R_DLY = 0; PLL1_N_DLY = 0 1850
ps
MODE = 2
PLL1_R_DLY = 0; PLL1_N_DLY = 0;
VCO Frequency = 2949.12 MHz
Analog delay select = 0;
Feedback clock digital delay = 11;
Feedback clock half step = 1;
Output clock digital delay = 5;
Output clock half step = 0;
0
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Electrical Characteristics (continued)
(3.15 V VCC 3.45 V, -40 °C TA85 °C. Typical values represent most likely parametric norms at VCC = 3.3 V, TA= 25
°C, at the Recommended Operating Conditions at the time of product characterization and are not ensured.)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
(16) See Typical Characteristics for output operation performance at higher frequencies than the minimum maximum output frequency.
LVDS CLOCK OUTPUTS (CLKoutX), CLKoutX_TYPE = 1
fCLKout Maximum frequency
(3) (16) RL= 100 Ω1536 MHz
VOD Differential output voltage
Figure 5
T = 25 °C, DC measurement
AC coupled to receiver input
R = 100 Ωdifferential termination
250 400 450 |mV|
VSS 500 800 900 mVpp
ΔVOD Change in Magnitude of VOD for
complementary output states –50 50 mV
VOS Output offset voltage 1.125 1.25 1.375 V
ΔVOS Change in VOS for complementary
output states 35 |mV|
TR/ TFOutput rise time 20% to 80%, RL = 100 Ω200 ps
Output fall time 80% to 20%, RL = 100 Ω
ISA
ISB Output short-circuit current: single
ended Single-ended output shorted to GND, T
= 25 °C –24 24 mA
ISAB Output short-circuit current: differential Complimentary outputs tied together –12 12 mA
LVPECL CLOCK OUTPUTS (CLKoutX)
fCLKout Maximum frequency
(3) (16) 1536 MHz
TR/ TF
20% to 80% output rise RL = 100 Ω, emitter resistors = 240 Ω
to GND
CLKoutX_TYPE = 4 or 5
(1600 or 2000 mVpp) 150 ps
80% to 20% output fall time
700-mVpp LVPECL CLOCK OUTPUTS (CLKoutX), CLKoutX_TYPE = 2
VOH Output high voltage
T = 25 °C, DC measurement
Termination = 50 Ωto
VCC - 1.4 V
VCC
1.03 V
VOL Output low voltage VCC
1.41 V
VOD Output voltage
Figure 5 305 380 440 |mV|
VSS 610 760 880 mVpp
1200-mVpp LVPECL CLOCK OUTPUTS (CLKoutX), CLKoutX_TYPE = 3
VOH Output high voltage
T = 25 °C, DC measurement
Termination = 50 Ωto
VCC 1.7 V
VCC
1.07 V
VOL Output low voltage VCC
1.69 V
VOD Output voltage
Figure 5 545 625 705 |mV|
VSS 1090 1250 1410 mVpp
1600-mVpp LVPECL CLOCK OUTPUTS (CLKoutX), CLKoutX_TYPE = 4
VOH Output high voltage
T = 25 °C, DC Measurement
Termination = 50 Ωto
VCC 2 V
VCC
1.10 V
VOL Output low voltage VCC
1.97 V
VOD Output voltage
Figure 5 660 870 965 |mV|
VSS 1320 1740 1930 mVpp
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Electrical Characteristics (continued)
(3.15 V VCC 3.45 V, -40 °C TA85 °C. Typical values represent most likely parametric norms at VCC = 3.3 V, TA= 25
°C, at the Recommended Operating Conditions at the time of product characterization and are not ensured.)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
2000-mVpp LVPECL (2VPECL) CLOCK OUTPUTS (CLKoutX), CLKoutX_TYPE = 5
VOH Output high voltage
T = 25 °C, DC Measurement
Termination = 50 Ωto
VCC 2.3 V
VCC
1.13 V
VOL Output low voltage VCC
2.20 V
VOD Output voltage
Figure 5 800 1070 1200 |mV|
VSS 1600 2140 2400 mVpp
LVCMOS CLOCK OUTPUTS (CLKoutX)
fCLKout Maximum frequency
(3) (16) 5-pF Load 250 MHz
VOH Output high voltage 1-mA Load VCC
0.1 V
VOL Output low voltage 1-mA Load 0.1 V
IOH Output high current (source) VCC = 3.3 V, VO= 1.65 V 28 mA
IOL Output low current (sink) VCC = 3.3 V, VO= 1.65 V 28 mA
DUTYCLK Output duty cycle
(3) VCC/2 to VCC/2, FCLK = 100 MHz, T =
25 °C 45% 50% 55%
TROutput rise time 20% to 80%, RL = 50 Ω,
CL = 5 pF 400 ps
TFOutput fall time 80% to 20%, RL = 50 Ω,
CL = 5 pF 400 ps
DIGITAL OUTPUTS (Status_CLKinX, Status_LD, Status_Holdover, SYNC)
VOH High-level output voltage IOH = -500 µA VCC
0.4 V
VOL Low-level output voltage IOL = 500 µA 0.4 V
DIGITAL INPUTS (Status_CLKinX, SYNC)
VIH High-level input voltage 1.6 VCC V
VIL Low-level input voltage 0.4 V
IIH High-level input current
VIH = VCC
Status_CLKinX_TYPE = 0
(High Impedance) –5 5
µA
Status_CLKinX_TYPE = 1
(Pull-up) –5 5
Status_CLKinX_TYPE = 2
(Pull-down) 10 80
IIL Low-level input current
VIL = 0 V
Status_CLKinX_TYPE = 0
(High Impedance) –5 5
µA
Status_CLKinX_TYPE = 1
(Pull-up) –40 –5
Status_CLKinX_TYPE = 2
(Pulldown) –5 5
DIGITAL INPUTS (CLKuWire, DATAuWire, LEuWire)
VIH High-level input voltage 1.6 VCC V
VIL Low-level input voltage 0.4 V
IIH High-level input current VIH = VCC 5 25 µA
IIL Low-level input current VIL = 0 –5 5 µA
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6.6 Timing Requirements MIN NOM MAX UNIT
TECS LE to Clock Set Up Time See Figure 6 25 ns
TDCS Data to Clock Set Up Time See Figure 6 25 ns
TCDH Clock to Data Hold Time See Figure 6 8 ns
TCWH Clock Pulse Width High See Figure 6 25 ns
TCWL Clock Pulse Width Low See Figure 6 25 ns
TCES Clock to LE Set Up Time See Figure 6 25 ns
TEWH LE Pulse Width See Figure 6 25 ns
TCR Falling Clock to Readback Time See Figure 9 25 ns
0 500 1000 1500 2000 2500 3000
0
200
400
600
800
1000
1200
VOD(mV)
FREQUENCY (MHz)
2000 mVpp
1600 mVpp
0 500 1000 1500 2000 2500 3000
0
200
400
600
800
1000
1200
VOD(mV)
FREQUENCY (MHz)
2000 mVpp
1600 mVpp
1200 mVpp
700 mVpp
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6.7 Typical Characteristics
Figure 1. LVDS VOD vs Frequency Figure 2. LVPECL With 240-ΩEmitter Resistors VOD vs
Frequency
Figure 3. LVPECL With 120-ΩEmitter Resistors VOD vs Frequency
CPout CPout
I2 I5
I Sink Vs I Source 100%
I2 I5
-
= ´
+
CPout CPout
I1 I3
I Vs V 100%
I1 I3
-
= ´
+
I4 I6
100%
I4 I6
-
= ´
+
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7 Parameter Measurement Information
7.1 Charge Pump Current Specification Definitions
I1 = Charge Pump Sink Current at VCPout = VCC -ΔV
I2 = Charge Pump Sink Current at VCPout = VCC/2
I3 = Charge Pump Sink Current at VCPout =ΔV
I4 = Charge Pump Source Current at VCPout = VCC -ΔV
I5 = Charge Pump Source Current at VCPout = VCC/2
I6 = Charge Pump Source Current at VCPout =ΔV
ΔV = Voltage offset from the positive and negative supply rails. Defined to be 0.5 V for this device.
7.1.1 Charge Pump Output Current Magnitude Variation Vs. Charge Pump Output Voltage
7.1.2 Charge Pump Sink Current Vs. Charge Pump Output Source Current Mismatch
VA
VB
GND
VID = | VA - VB | VSS = 2·VID
VID Definition VSS Definition for Input
Non-Inverting Clock
Inverting Clock
VID 2·VID
AA
A
2 T 2 T 25 C
CPout A
2 T 25 C
I I
I Vs T 100%
I
= °
= °
-
= ´
AA
A
5 T 5 T 25 C
5 T 25 C
I I
100%
I
= °
= °
-
= ´
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Charge Pump Current Specification Definitions (continued)
7.1.3 Charge Pump Output Current Magnitude Variation vs Temperature
7.2 Differential Voltage Measurement Terminology
The differential voltage of a differential signal can be described by two different definitions causing confusion
when reading datasheets or communicating with other engineers. This section will address the measurement and
description of a differential signal so that the reader will be able to understand and discern between the two
different definitions when used.
The first definition used to describe a differential signal is the absolute value of the voltage potential between the
inverting and non-inverting signal. The symbol for this first measurement is typically VID or VOD depending on if
an input or output voltage is being described.
The second definition used to describe a differential signal is to measure the potential of the non-inverting signal
with respect to the inverting signal. The symbol for this second measurement is VSS and is a calculated
parameter. Nowhere in the IC does this signal exist with respect to ground, it only exists in reference to its
differential pair. VSS can be measured directly by oscilloscopes with floating references, otherwise this value can
be calculated as twice the value of VOD as described in the first description.
Figure 4 illustrates the two different definitions side-by-side for inputs and Figure 5 illustrates the two different
definitions side-by-side for outputs. The VID and VOD definitions show VAand VBDC levels that the non-inverting
and inverting signals toggle between with respect to ground. VSS input and output definitions show that if the
inverting signal is considered the voltage potential reference, the non-inverting signal voltage potential is now
increasing and decreasing above and below the non-inverting reference. Thus the peak-to-peak voltage of the
differential signal can be measured.
VID and VOD are often defined as volts (V) and VSS is often defined as volts peak-to-peak (VPP).
Figure 4. Two Different Definitions for Differential Input Signals
VA
VB
GND
VOD = | VA - VB | VSS = 2·VOD
VOD Definition VSS Definition for Output
Non-Inverting Clock
Inverting Clock
VOD 2·VOD
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Differential Voltage Measurement Terminology (continued)
See the AN-912 Common Data Transmission Parameters and Their Definitions (SNLA036) application note for more
information.
Figure 5. Two Different Definitions for Differential Output Signals
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8 Detailed Description
8.1 Overview
In default mode of operation, dual PLL mode with internal VCO, the Phase Frequency Detector in PLL1
compares the active CLKinX reference divided by CLKinX_PreR_DIV and PLL1 R divider with the external
VCXO or crystal attached to the PLL2 OSCin port divided by PLL1 N divider. The external loop filter for PLL1
should be narrow to provide an ultra clean reference clock from the external VCXO or crystal to the
OSCin/OSCin* pins for PLL2.
The Phase Frequency Detector in PLL2 compares the external VCXO or crystal attached to the OCSin port
divided by the PLL2 R divider with the output of the internal VCO divided by the PLL2 N divider and N2 pre-
scaler and optionally the VCO divider. The bandwidth of the external loop filter for PLL2 should be designed to
be wide enough to take advantage of the low in-band phase noise of PLL2 and the low high offset phase noise of
the internal VCO. The VCO output is also placed on the distribution path for the clock distribution section. The
clock distribution consists of 6 dividers and delays which drive 6 outputs. Each clock output allows the user to
select a divide value, a digital delay value, and an analog delay. The 6 dividers drive programmable output
buffers. Two outputs allow their input signal to be from the OSCin port directly.
When a 0-delay mode is used, a clock output will be passed through the feedback mux to the PLL1 N Divider for
synchronization and 0-delay.
When an external VCO mode is used, the Fin port will be used to input an external VCO signal. PLL2 Phase
comparison will now be with this signal divided by the PLL2 N divider and N2 pre-scaler. The VCO divider may
not be used. One less clock input is available when using an external VCO mode.
When a single PLL mode is used, PLL1 is powered down. OSCin is used as a reference to PLL2.
8.1.1 System Architecture
The dual loop PLL architecture of the LMK04906 provides the lowest jitter performance over the widest range of
output frequencies and phase noise integration bandwidths. The first stage PLL (PLL1) is driven by an external
reference clock and uses an external VCXO or tunable crystal to provide a frequency accurate, low phase noise
reference clock for the second stage frequency multiplication PLL (PLL2). PLL1 typically uses a narrow loop
bandwidth (10 Hz to 200 Hz) to retain the frequency accuracy of the reference clock input signal while at the
same time suppressing the higher offset frequency phase noise that the reference clock may have accumulated
along its path or from other circuits. This “cleaned” reference clock provides the reference input to PLL2.
The low phase noise reference provided to PLL2 allows PLL2 to operate with a wide loop bandwidth (50 kHz to
200 kHz). The loop bandwidth for PLL2 is chosen to take advantage of the superior high offset frequency phase
noise profile of the internal VCO and the good low offset frequency phase noise of the reference VCXO or
tunable crystal.
Ultra low jitter is achieved by allowing the external VCXO or Crystal’s phase noise to dominate the final output
phase noise at low offset frequencies and the internal VCO’s phase noise to dominate the final output phase
noise at high offset frequencies. This results in best overall phase noise and jitter performance.
The LMK04906 allows subsets of the device to be used to increase the flexibility of device. These different
modes are selected using MODE: Device Mode. For instance:
Dual Loop Mode - Typical use case of LMK04906. CLKinX used as reference input to PLL1, OSCin port is
connected to VCXO or tunable crystal.
Single Loop Mode - Powers down PLL1. OSCin port is used as reference input.
Clock Distribution Mode - Allows input of CLKin1 to be distributed to output with division, digital delay, and
analog delay.
See Device Functional Modes for more information on these modes.
8.1.2 PLL1 Redundant Reference Inputs (CLKin0/CLKin0*, CLKin1/CLKin1*, and CLKin2/CLKin2*)
The LMK04906 has three reference clock inputs for PLL1, CLKin0, CLKin1, and CLKin2. Ref Mux selects
CLKin0, CLKin1, or CLKin2. Automatic or manual switching occurs between the inputs.
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Overview (continued)
CLKin0, CLKin1, and CLKin2 each have input dividers. The input divider allows different clock input frequencies
to be normalized so that the frequency input to the PLL1 R divider remains constant during automatic switching.
By programming these dividers such that the frequency presented to the input of the PLL1_R divider is the same
prevents the user from needing to reprogram the PLL1 R divider when the input reference is changed to another
CLKin port with a different frequency.
CLKin1 is shared for use as an external 0-delay feedback (FBCLKin), or for use with an external VCO (Fin).
Fast manual switching between reference clocks is possible with a external pins Status_CLKin0, Status_CLKin1,
Status_CLKin2. If Status_CLKinx pins are used to select the reference clock, a minimum pulse width of 500ns
must be met.
8.1.3 PLL1 Tunable Crystal Support
The LMK04906 integrates a crystal oscillator on PLL1 for use with an external crystal and varactor diode to
perform jitter cleaning.
The LMK04906 must be programmed to enable Crystal mode.
8.1.4 VCXO/Crystal Buffered Outputs
The LMK04906 provides a dedicated output which is a buffered copy of the PLL2 reference input. This reference
input is typically a low noise VCXO or Crystal. When using a VCXO, this output can be used to clock external
devices such as microcontrollers, FPGAs, CPLDs, etc. before the LMK04906 is programmed.
The OSCout0 buffer output type is programmable to LVDS, LVPECL, or LVCMOS.
The dedicated output buffer OSCout0 can output frequency lower than the VCXO or Crystal frequency by
programming the OSC Divider. The OSC Divider value range is 1 to 8. Each OSCoutX can individually choose to
use the OSC Divider output or to bypass the OSC Divider.
Two clock outputs can also be programmed to be driven by OSCin. This allows a total of 2 additional differential
outputs to be buffered outputs of OSCin. When programmed in this way, a total of 3 differential outputs can be
driven by a buffered copy of OSCin.
VCXO/Crystal buffered outputs cannot be synchronized to the VCO clock distribution outputs. The assertion of
SYNC will still cause these outputs to become low. Since these outputs will turn off and on asynchronously with
respect to the VCO sourced clock outputs during a SYNC, it is possible for glitches to occur on the buffered clock
outputs when SYNC is asserted and unasserted. If the NO_SYNC_CLKoutX bits are set these outputs will not be
affected by the SYNC event except that the phase relationship will change with the other synchronized clocks
unless a buffered clock output is used as a qualification clock during SYNC.
8.1.5 Frequency Holdover
The LMK04906 supports holdover operation to keep the clock outputs on frequency with minimum drift when the
reference is lost until a valid reference clock signal is re-established.
8.1.6 Integrated Loop Filter Poles
The LMK04906 features programmable 3rd and 4th order loop filter poles for PLL2. These internal resistors and
capacitor values may be selected from a fixed range of values to achieve either a 3rd or 4th order loop filter
response. The integrated programmable resistors and capacitors compliment external components mounted near
the chip.
These integrated components can be effectively disabled by programming the integrated resistors and capacitors
to their minimum values.
8.1.7 Internal VCO
The output of the internal VCO is routed to a mux which allows the user to select either the direct VCO output or
a divided version of the VCO for the Clock Distribution Path. This same selection is also fed back to the PLL2
phase detector through a prescaler and N-divider.
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Overview (continued)
The mux selectable VCO divider has a divide range of 2 to 8 with 50% output duty cycle for both even and odd
divide values.
The primary use of the VCO divider is to achieve divides greater than the clock output divider supports alone.
8.1.8 External VCO Mode
The Fin/Fin* input allows an external VCO to be used with PLL2 of the LMK04906.
Using an external VCO reduces the number of available clock inputs by one.
8.1.9 Clock Distribution
The LMK04906 features a total of 6 outputs driven from the internal or external VCO.
All VCO driven outputs have programmable output types. They can be programmed to LVPECL, LVDS, or
LVCMOS. When all distribution outputs are configured for LVCMOS or single ended LVPECL a total of 24
outputs are available.
If the buffered OSCin output OSCout0 is included in the total number of clock outputs the LMK04906 is able to
distribute, then up to 6 differential clocks or up to 12 single ended clocks may be generated with the LMK04906.
The following sections discuss specific features of the clock distribution channels that allow the user to control
various aspects of the output clocks.
8.1.9.1 CLKout DIVIDER
Each clock output has a single clock output divider. The divider supports a divide range of 1 to 1045 (even and
odd) with 50% output duty cycle. When divides of 26 or greater are used, the divider/delay block uses extended
mode.
The VCO Divider may be used to reduce the divide needed by the clock output divider so that it may operate in
normal mode instead of extended mode. This can result in a small current saving if enabling the VCO Divider
allows 3 or more clock output divides to change from extended to normal mode.
8.1.9.2 CLKout Delay
The clock distribution section includes both a fine (analog) and coarse (digital) delay for phase adjustment of the
clock outputs.
The fine (analog) delay allows a nominal 25 ps step size and range from 0 to 475 ps of total delay. Enabling the
analog delay adds a nominal 500 ps of delay in addition to the programmed value. When adjusting analog delay,
glitches may occur on the clock outputs being adjusted. Analog delay may not operate at frequencies above the
minimum-specified maximum output frequency of 1536 MHz.
The coarse (digital) delay allows a group of outputs to be delayed by 4.5 to 12 clock distribution path cycles in
normal mode, or from 12.5 to 522 VCO cycles in extended mode. The delay step can be as small as half the
period of the clock distribution path by using the CLKoutX_HS bit provided the output divide value is greater than
1. For example 2 GHz VCO frequency without using the VCO divider results in 250 ps coarse tuning steps. The
coarse (digital) delay value takes effect on the clock outputs after a SYNC event.
There are 3 different ways to use the digital (coarse) delay.
1. Fixed Digital Delay
2. Absolute Dynamic Digital Delay
3. Relative Dynamic Digital Delay
8.1.9.3 Programmable Output Type
For increased flexibility all LMK04906 clock outputs (CLKoutX) and OSCout0 can be programmed to an LVDS,
LVPECL, or LVCMOS output type.
Any LVPECL output type can be programmed to 700, 1200, 1600, or 2000 mVpp amplitude levels. The 2000
mVpp LVPECL output type is a Texas Instruments proprietary configuration that produces a 2000 mVpp
differential swing for compatibility with many data converters and is also known as 2VPECL.
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Overview (continued)
8.1.9.4 Clock Output Synchronization
Using the SYNC input causes all active clock outputs to share a rising edge. See Clock Output Synchronization
(SYNC) for more information.
The SYNC event also causes the digital delay values to take effect.
8.1.10 0-Delay
The 0-delay mode synchronizes the input clock phase to the output clock phase. The 0-delay feedback may
performed with an internal feedback loop from some of the clock outputs or with an external feedback loop into
the FBCLKin port as selected by the FEEDBACK_MUX.
Without using 0-delay mode there will be n possible fixed phase relationships from clock input to clock output
depending on the clock output divide value.
Using an external 0-delay feedback reduces the number of available clock inputs by one.
8.1.11 Default Start-Up Clocks
Before the LMK04906 is programmed, CLKout4 is enabled and operating at a nominal frequency and CLKout3
and OSCout0 are enabled and operating at the OSCin frequency. These clocks can be used to clock external
devices such as microcontrollers, FPGAs, CPLDs, etc. before the LMK04906 is programmed.
For CLKout3 and OSCout0 to work before the LMK04906 is programmed the device must not be using Crystal
mode.
8.1.12 Status Pins
The LMK04906 provides status pins which can be monitored for feedback or in some cases used for input
depending upon device programming. For example:
The Status_Holdover pin may indicate if the device is in hold-over mode.
The Status_CLKin0 pin may indicate the LOS (loss-of-signal) for CLKin0.
The Status_CLKin0 pin may be an input for selecting the active clock input.
The Status_LD pin may indicate if the device is locked.
The status pins can be programmed to a variety of other outputs including analog lock detect, PLL divider
outputs, combined PLL lock detect signals, PLL1 Vtune railing, readback, and so forth. See Status PINS of this
data sheet for more information. Default pin programming is captured in Table 17.
8.1.13 Register Readback
Programmed registers may be read back using the MICROWIRE interface. For readback one of the status pins
must be programmed for readback mode.
At no time may registers be programed to values other than the valid states defined in the data sheet.
CLKuWire
DATAuWire
LEuWire
R1 Divider
(1 to 16,383)
CPout1
Internal VCO
Partially
Integrated
Loop Filter
2X
Mux
R Delay
N Delay
OSCin*
OSCin
FB
Mux
2X
Control
Registers
PWire
Port
SYNC/
Status_CLKin2
Status_LD
Status_Holdover
Status_CLKin0
Device
Control
Status_CLKin1
Holdover
CLKin0*
CLKin0
Divider
(1 to 1045) Digital
Delay
CLKout1
CLKout3
CLKout4
CLKout5
VCO Divider
(2 to 8)
Osc
Mux1
Osc
Mux2
CPout2
CLKin0 Divider
(1, 2, 4, or 8)
N1 Divider
(1 to 16,383)
R2 Divider
(1 to 4,095)
Phase
Detector
PLL1
Phase
Detector
PLL2
N2 Divider
(1 to 262,143)
Delay
Clock Buffer 2
Clock Buffer 1
Clock Buffer 1
Clock Buffer 3
Clock Distribution PathN2 Prescaler
(2 to 8)
VCO
Mux
Fin/Fin*
Fin/Fin*
CLKin1 Divider
(1, 2, 4, or 8)
OSCout0
OSCout0* OSCout0
_MUX OSC Divider
(2 to 8)
CLKin1*/Fin*
FBCLKin*
CLKin1/
Fin/FBCLKin
Mode
Mux2
Mode
Mux1
OSCout0
_MUX Mode
Mux3
FBMux
FBMux
CLKin2*
CLKin2
CLKin2 Divider
(1, 2, 4, or 8)
Ref
Mux
CLKout0
CLKout0*
Mux
Divider
(1 to 1045) Digital
Delay
Delay
CLKout1
CLKout1*
Mux
Divider
(1 to 1045) Digital
Delay
Delay
CLKout2
CLKout2*
Mux
Divider
(1 to 1045)
Digital
Delay Delay
CLKout4
CLKout4*
Mux
Divider
(1 to 1045)
Digital
Delay Delay
CLKout5
CLKout5*
Mux
Divider
(1 to 1045)
Digital
Delay Delay
CLKout3
CLKout3*
Mux
Copyright © 2016, Texas Instruments Incorporated
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8.2 Functional Block Diagram
8.3 Feature Description
8.3.1 Serial MICROWIRE Timing Diagram
Register programming information on the DATAuWire pin is clocked into a shift register on each rising edge of
the CLKuWire signal. On the rising edge of the LEuWire signal, the register is sent from the shift register to the
register addressed. A slew rate of at least 30 V/µs is recommended for these signals. After programming is
complete the CLKuWire, DATAuWire, and LEuWire signals should be returned to a low state. If the CLKuWire or
DATAuWire lines are toggled while the VCO is in lock, as is sometimes the case when these lines are shared
with other parts, the phase noise may be degraded during this programming. See Figure 6 for timing diagram.
D26 A0
MSB LSB
DATAuWire
CLKuWire
LEuWire
tCES
tCES tECS
D26 A0
MSB LSB
DATAuWire
CLKuWire
LEuWire
tECS
tEWH
tCWH
tCWL
tCES
tDCS
D26 D25 D24 D23
tCDH tCWH tCWL
D22 D0 A4 A1 A0
MSB LSB
DATAuWire
CLKuWire
LEuWire
tCES
tEWH
tECS
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Feature Description (continued)
Figure 6. MICROWIRE Timing Diagram
8.3.2 Advanced MICROWIRE Timing Diagrams
8.3.2.1 Three Extra Clocks or Double Program
Figure 7 shows the timing for the programming sequence for loading CLKoutX_DIV > 25 or CLKoutX_DDLY > 12
as described in Special Programming Case for R0 to R5 for CLKoutX_DIV and CLKoutX_DDLY.
Figure 7. MICROWIRE Timing Diagram: Extra CLKuWire Pulses for R0 to R5
8.3.2.2 Three Extra Clocks With LEuWire High
Figure 8 shows the timing for the programming sequence which allows SYNC_EN_AUTO = 1 when loading
CLKoutX_DIV > 25 or CLKoutX_DDLY > 12. When SYNC_EN_AUTO = 1, a SYNC event is automatically
generated on the falling edge of LEuWire. See Special Programming Case for R0 to R5 for CLKoutX_DIV and
CLKoutX_DDLY.
Figure 8. MICROWIRE Timing Diagram: Extra CLKuWire Pulses for R0 to R5 With LEuWire Asserted
D26 A0
MSB LSB
DATAuWire
CLKuWire
LEuWire
READBACK_LE = 0
tECS
tEWH
Readback Pin RD0RD24RD26
LEuWire
READBACK_LE = 1
tCWH
tCWL
RD25
tCR
RD23
tCR
tECS
Register Write Register Read
tCES
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Feature Description (continued)
8.3.2.3 Readback
For timing specifications, see Timing Requirements. See Readback for more information on performing a
readback operation. Figure 9 shows timing for LEuWire for both READBACK_LE = 1 and 0.
The rising edges of CLKuWire during MICROWIRE readback continue to clock data on DATAuWire into the
device during readback. If after the readback, LEuWire transitions from low to high, this data will be latched to
the decoded register. The decoded register address consists of the last 5 bits clocked on DATAuWire as shown
in the MICROWIRE Timing Diagrams.
Figure 9. MICROWIRE Readback Timing Diagram
8.3.3 Inputs / Outputs
8.3.3.1 PLL1 Reference Inputs (CLKin0, CLKin1, and CLKin2)
The reference clock inputs for PLL1 may be selected from either CLKin0, CLKin1, or CLKin2. The user has the
capability to manually select one of the inputs or to configure an automatic switching mode of operation. See
Input Clock Switching for more info.
CLKin0, CLKin1, and CLKin2 have dividers which allow the device to switch between reference inputs of different
frequencies automatically without needing to reprogram the PLL1 R divider. The CLKin pre-divider values are 1,
2, 4, and 8.
CLKin1 input can alternatively be used for external feedback in 0-delay mode (FBCLKin) or for an external VCO
input port (Fin).
8.3.3.2 PLL2 OSCin / OSCin* Port
The feedback from the external oscillator being locked with PLL1 drives the OSCin/OSCin* pins. Internally this
signal is routed to the PLL1 N Divider and to the reference input for PLL2.
This input may be driven with either a single-ended or differential signal and must be AC coupled. If operated in
single ended mode, the unused input must be connected to GND with a 0.1-µF capacitor.
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Feature Description (continued)
8.3.3.3 Crystal Oscillator
The internal circuitry of the OSCin port also supports the optional implementation of a crystal based oscillator
circuit. A crystal, a varactor diode, and a small number of other external components may be used to implement
the oscillator. The internal oscillator circuit is enabled by setting the EN_PLL2_XTAL bit. See EN_PLL2_XTAL.
8.3.4 Input Clock Switching
Manual, pin select, and automatic are three different kinds clock input switching modes can be set with the
CLKin_SELECT_MODE register.
Below is information about how the active input clock is selected and what causes a switching event in the
various clock input selection modes.
8.3.4.1 Input Clock Switching - Manual Mode
When CLKin_SELECT_MODE is 0, 1, or 2 then CLKin0, CLKin1, or CLKin2 respectively is always selected as
the active input clock. Manual mode will also override the EN_CLKinX bits such that the CLKinX buffer will
operate even if CLKinX is is disabled with EN_CLKinX = 0.
Entering Holdover
If holdover mode is enabled then holdover mode is entered if:
Digital lock detect of PLL1 goes low and DISABLE_DLD1_DET = 0.
Exiting Holdover
The active clock for automatic exit of holdover mode is the manually selected clock input.
8.3.4.2 Input Clock Switching - Pin Select Mode
When CLKin_SELECT_MODE is 3, the pins Status_CLKin0 and Status_CLKin1 select which clock input is
active.
Clock Switch Event: Pins
Changing the state of Status_CLKin0 or Status_CLKin1 pins causes an input clock switch event.
Clock Switch Event: PLL1 DLD
To prevent PLL1 DLD high to low transition from causing a input clock switch event and causing the device to
enter holdover mode, disable the PLL1 DLD detect by setting DISABLE_DLD1_DET = 1. This is the preferred
behavior for Pin Select Mode.
Configuring Pin Select Mode
The Status_CLKin0_TYPE must be programmed to an input value for the Status_CLKin0 pin to function as an
input for pin select mode.
The Status_CLKin1_TYPE must be programmed to an input value for the Status_CLKin1 pin to function as an
input for pin select mode.
If the Status_CLKinX_TYPE is set as output, the input value is considered "0."
Table 1 defines which input clock is active depending on Status_CLKin0 and Status_CLKin1 state.
Table 1. Active Clock Input Pin Select Mode
Status_CLKin1 Status_CLKin0 ACTIVE CLOCK
0 0 CLKin0
0 1 CLKin1
1 0 CLKin2
1 1 Holdover
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The pin select mode will override the EN_CLKinX bits such that the CLKinX buffer will operate even if CLKinX is
is disabled with EN_CLKinX = 0. To switch as fast as possible, keep the clock input buffers enabled (EN_CLKinX
= 1) that could be switched to.
8.3.4.2.1 Pin Select Mode and Host
When in the pin select mode, the host can monitor conditions of the clocking system which could cause the host
to switch the active clock input. The LMK04906 device can also provide indicators on the Status_LD and
Status_HOLDOVER like "DAC Rail," "PLL1 DLD", "PLL1 & PLL2 DLD" which the host can use in determining
which clock input to use as active clock input.
8.3.4.2.2 Switch Event Without Holdover
When an input clock switch event is triggered and holdover mode is disabled, the active clock input immediately
switches to the selected clock. When PLL1 is designed with a narrow loop bandwidth, the switching transient is
minimized.
8.3.4.2.3 Switch Event With Holdover
When an input clock switch event is triggered and holdover mode is enabled, the device will enter holdover mode
and remain in holdover until a holdover exit condition is met as described in Holdover Mode. Then the device will
complete the reference switch to the pin selected clock input.
8.3.4.3 Input Clock Switching Automatic Mode
When CLKin_SELECT_MODE is 4, the active clock is selected in priority order of enabled clock inputs starting
upon an input clock switch event. The priority order of the clocks is CLKin0 CLKin1 CLKin2, etc.
For a clock input to be eligible to be switched through, it must be enabled using EN_CLKinX.
8.3.4.3.1 Starting Active Clock
Upon programming this mode, the currently active clock remains active if PLL1 lock detect is high. To ensure a
particular clock input is the active clock when starting this mode, program CLKin_SELECT_MODE to the manual
mode which selects the desired clock input (CLKin0, 1, or 2). Wait for PLL1 to lock PLL1_DLD = 1, then select
this mode with CLKin_SELECT_MODE = 4.
8.3.4.3.2 Clock Switch Event: PLL1 DLD
A loss of lock as indicated by PLL1’s DLD signal (PLL1_DLD = 0) will cause an input clock switch event if
DISABLE_DLD1_DET = 0. PLL1 DLD must go high (PLL1_DLD = 1) in between input clock switching events.
8.3.4.3.3 Clock Switch Event: PLL1 Vtune Rail
If Vtune_RAIL_DET_EN is set and the PLL1 Vtune voltage crosses the DAC high or low threshold, holdover
mode will be entered. Since PLL1_DLD = 0 in holdover a clock input switching event will occur.
8.3.4.3.4 Clock Switch Event With Holdover
Holdover mode is entered and the active clock is set to the next enabled clock input in priority order. When the
new active clock meets the holdover exit conditions, holdover is exited and the active clock will continue to be
used as a reference until another PLL1 loss of lock event. PLL1 DLD must go high in between input clock
switching events.
8.3.4.3.5 Clock Switch Event Without Holdover
If holdover is not enabled and an input clock switch event occurs, the active clock is set to the next enabled clock
in priority order. The LMK04906 will keep this new input clock as the active clock until another input clock
switching event. PLL1 DLD must go high in between input clock switching events.
8.3.4.4 Input Clock Switching - Automatic Mode With Pin Select
When CLKin_SELECT_MODE is 6, the active clock is selected using the Status_CLKinX pins upon an input
clock switch event according to Table 2.
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8.3.4.4.1 Starting Active Clock
Upon programming this mode, the currently active clock remains active if PLL1 lock detect is high. To ensure a
particular clock input is the active clock when starting this mode, program CLKin_SELECT_MODE to the manual
mode which selects the desired clock input (CLKin0 or 1). Wait for PLL1 to lock PLL1_DLD = 1, then select this
mode with CLKin_SELECT_MODE = 6.
8.3.4.4.2 Clock Switch Event: PLL1 DLD
An input clock switch event is generated by a loss of lock as indicated by PLL1's DLD signal (PLL1 DLD = 0).
8.3.4.4.3 Clock Switch Event: PLL1 Vtune Rail
If Vtune_RAIL_DET_EN is set and the PLL1 Vtune voltage crosses the DAC threshold, holdover mode will be
entered. Since PLL1_DLD = 0 in holdover, a clock input switching event will occur.
8.3.4.4.4 Clock Switch Event With Holdover
Clock switch event with holdover enabled is recommended in this input clock switching mode. When an input
clock switch event occurs, holdover mode is entered and the active clock is set to the clock input defined by the
Status_CLKinX pins. When the new active clock meets the holdover exit conditions, holdover is exited and the
active clock will continue to be used as a reference until another input clock switch event. PLL1 DLD must go
high in between input clock switching events.
Table 2. Active Clock Input - Auto Pin Mode
Status_CLKin1 Status_CLKin0 ACTIVE CLOCK
X 1 CLKin0
1 0 CLKin1
0 0 CLKin2
The polarity of Status_CLKin1 and Status_CLKin0 input pins can be inverted with the CLKin_SEL_INV bit.
8.3.5 Holdover Mode
Holdover mode causes PLL2 to stay locked on frequency with minimal frequency drift when an input clock
reference to PLL1 becomes invalid. While in holdover mode, the PLL1 charge pump is TRI-STATED and a fixed
tuning voltage is set on CPout1 to operate PLL1 in open loop.
8.3.5.1 Enable Holdover
Program HOLDOVER_MODE to enable holdover mode. Holdover mode can be manually enabled by
programming the FORCE_HOLDOVER bit.
The holdover mode can be set to operate in 2 different sub-modes.
Fixed CPout1 (EN_TRACK = 0 or 1, EN_MAN_DAC = 1).
Tracked CPout1 (EN_TRACK = 1, EN_MAN_DAC = 0).
Not valid when EN_VTUNE_RAIL_DET = 1.
Updates to the DAC value for the Tracked CPout1 sub-mode occurs at the rate of the PLL1 phase detector
frequency divided by DAC_CLK_DIV. These updates occur any time EN_TRACK = 1.
The DAC update rate should be programmed for <= 100 kHz to ensure DAC holdover accuracy.
When tracking is enabled the current voltage of DAC can be readback, see DAC_CNT.
8.3.5.2 Entering Holdover
The holdover mode is entered as described in Input Clock Switching. Typically this is because:
FORCE_HOLDOVER bit is set.
PLL1 loses lock according to PLL1_DLD, and
HOLDOVER_MODE = 2
DISABLE_DLD1_DET = 0
Holdover accuracy (ppm) = ± 6.4 mV × Kv × 1e6
VCXO Frequency
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CPout1 voltage crosses DAC high or low threshold, and
HOLDOVER_MODE = 2
EN_VTUNE_RAIL_DET = 1
EN_TRACK = 1
DAC_HIGH_TRIP = User Value
DAC_LOW_TRIP = User Value
EN_MAN_DAC = 1
MAN_DAC = User Value
8.3.5.3 During Holdover
PLL1 is run in open loop mode.
PLL1 charge pump is set to TRI-STATE.
PLL1 DLD will be unasserted.
The HOLDOVER status is asserted
During holdover If PLL2 was locked prior to entry of holdover mode, PLL2 DLD will continue to be asserted.
CPout1 voltage will be set to:
a voltage set in the MAN_DAC register (fixed CPout1).
a voltage determined to be the last valid CPout1 voltage (tracked CPout1).
PLL1 DLD will attempt to lock with the active clock input.
The HOLDOVER status signal can be monitored on the Status_HOLDOVER or Status_LD pin by programming
the HOLDOVER_MUX or LD_MUX register to "Holdover Status."
8.3.5.4 Exiting Holdover
Holdover mode can be exited in one of two ways.
Manually, by programming the device from the host.
Automatically, By a clock operating within a specified ppm of the current PLL1 frequency on the active clock
input. See Input Clock Switching for more detail on which clock input is active.
To exit holdover by programming, set HOLDOVER_MODE = Disabled. HOLDOVER_MODE can then be re-
enabled by programming HOLDOVER_MODE = Enabled. Care should be taken to ensure that the active clock
upon exiting holdover is as expected, otherwise the CLKin_SELECT_MODE register may need to be re-
programmed.
8.3.5.5 Holdover Frequency Accuracy and DAC Performance
When in holdover mode PLL1 will run in open loop and the DAC will set the CPout1 voltage. If Fixed CPout1
mode is used, then the output of the DAC will be a voltage dependant upon the MAN_DAC register. If Tracked
CPout1 mode is used, then the output of the DAC will be the voltage at the CPout1 pin before holdover mode
was entered. When using Tracked mode and EN_MAN_DAC = 1, during holdover the DAC value is loaded with
the programmed value in MAN_DAC, not the tracked value.
When in Tracked CPout1 mode the DAC has a worst case tracking error of ±2 LSBs once PLL1 tuning voltage is
acquired. The step size is approximately 3.2 mV; therefore, the VCXO frequency error during holdover mode
caused by the DAC tracking accuracy is ±6.4 mV × Kv. Where Kv is the tuning sensitivity of the VCXO in use.
Therefore the accuracy of the system when in holdover mode in ppm is:
(1)
Example: consider a system with a 19.2 MHz clock input, a 153.6 MHz VCXO with a Kv of 17 kHz/V. The
accuracy of the system in holdover in ppm is:
±0.71 ppm = ±6.4 mV × 17 kHz/V × 1e6 / 153.6 MHz
It is important to account for this frequency error when determining the allowable frequency error window to
cause holdover mode to exit.
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8.3.5.6 Holdover Mode - Automatic Exit of Holdover
The LMK04906 device can be programmed to automatically exit holdover mode when the accuracy of the
frequency on the active clock input achieves a specified accuracy. The programmable variables include
PLL1_WND_SIZE and DLD_HOLD_CNT.
See Digital Lock Detect Frequency Accuracy to calculate the register values to cause holdover to automatically
exit upon reference signal recovery to within a user specified ppm error of the holdover frequency.
It is possible for the time to exit holdover to vary because the condition for automatic holdover exit is for the
reference and feedback signals to have a time/phase error less than a programmable value. Because it is
possible for two clock signals to be very close in frequency but not close in phase, it may take a long time for the
phases of the clocks to align themselves within the allowable time/phase error before holdover exits.
8.3.6 PLLs
8.3.6.1 PLL1
PLL1's maximum phase detector frequency (fPD1) is 40 MHz. Since a narrow loop bandwidth should be used for
PLL1, the need to operate at high phase detector rate to lower the in-band phase noise becomes unnecessary.
The maximum values for the PLL1 R and N dividers is 16,383. Charge pump current ranges from 100 to 1600
µA. PLL1 N divider may be driven by OSCin port at the OSCout0_MUX output (default) or by internal or external
feedback as selected by Feedback Mux in 0-delay mode.
Low charge pump currents and phase detector frequencies aid design of low loop bandwidth loop filters with
reasonably sized components to allow the VCXO or PLL2 to dominate phase noise inside of PLL2 loop
bandwidth. High charge pump currents may be used by PLL1 when using VCXOs with leaky tuning voltage
inputs to improve system performance.
8.3.6.2 PLL2
PLL2's maximum phase detector frequency (fPD2) is 155 MHz. Operating at highest possible phase detector rate
will ensure low in-band phase noise for PLL2 which in turn produces lower total jitter. The in-band phase noise
from the reference input and PLL is proportional to N2. The maximum value for the PLL2 R divider is 4,095. The
maximum value for the PLL2 N divider is 262,143. The N2 Prescaler in the total N feedback path can be
programmed for values 2 to 8 (all divides even and odd). Charge pump current ranges from 100 to 3200 µA.
High charge pump currents help to widen the PLL2 loop bandwidth to optimize PLL2 performance.
8.3.6.2.1 PLL2 Frequency Doubler
The PLL2 reference input at the OSCin port may be routed through a frequency doubler before the PLL2 R
Divider. The frequency doubler feature allows the phase comparison frequency to be increased when a relatively
low frequency oscillator is driving the OSCin port. By doubling the PLL2 phase detector frequency, the in-band
PLL2 noise is reduced by about 3 dB.
For applications in which the OSCin frequency and PLL2 phase detector frequency are equal, the best PLL2 in-
band noise can be achieved when the doubler is enabled (EN_PLL2_REF_2X = 1) and the PLL2 R divide value
is 2. Do not use doubler disabled (EN_PLL2_REF_2X = 0) and PLL2 R divide value of 1.
When using the doubler take care to use the PLL2 R Divider to reduce the phase detector frequency to the limit
of the PLL2 maximum phase detector frequency.
8.3.6.3 Digital Lock Detect
Both PLL1 and PLL2 support digital lock detect. Digital lock detect compares the phase between the reference
path (R) and the feedback path (N) of the PLL. When the time error, which is phase error, between the two
signals is less than a specified window size (ε) a lock detect count increments. When the lock detect count
reaches a user specified value lock detect is asserted true. Once digital lock detect is true, a single phase
comparison outside the specified window will cause digital lock detect to be asserted false. This is illustrated in
Figure 10.
The incremental lock detect count feature functions as a digital filter to ensure that lock detect isn't asserted for
only a brief time when the phases of R and N are within the specified tolerance for only a brief time during initial
phase lock.
NO
NO
YES
YES
YES
Phase Error < â
PLLX
Lock Detected = False
Lock Count = 0
PLLX Lock Count =
PLLX_DLD_CNT
Phase Error > â
NO YES
START
Increment
PLLX Lock Count
PLLX
Lock Detected = True
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The digital lock detect signal can be monitored on the Status_LD or Status_Holdover pin. The pin may be
programmed to output the status of lock detect for PLL1, PLL2, or both PLL1 and PLL2.
See Digital Lock Detect Frequency Accuracy for more detailed information on programming the registers to
achieve a specified frequency accuracy in ppm with lock detect.
The digital lock detect feature can also be used with holdover to automatically exit holdover mode. See Holdover
Mode for more info.
Figure 10. Digital Lock Detect Flowchart
8.3.7 Status PINS
The Status_LD, Status_HOLDOVER, Status_CLKin0, Status_CLKin1, and SYNC/Status_CLKin2 pins can be
programmed to output a variety of signals for indicating various statuses like digital lock detect, holdover, several
DAC indicators, and several PLL divider outputs.
8.3.7.1 Logic Low
This is a vary simple output. In combination with the output _MUX register, this output can be toggled between
high and low. Useful to confirm MICROWIRE programming or as a general purpose IO.
8.3.7.2 Digital Lock Detect
PLL1 DLD, PLL2 DLD, and PLL1 + PLL2 are selectable on certain output pins. See Digital Lock Detect for more
information.
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8.3.7.3 Holdover Status
Indicates if the device is in Holdover mode. See Holdover Mode for more information.
8.3.7.4 DAC
Various flags for the DAC can be monitored including DAC Locked, DAC Rail, DAC Low, and DAC High.
When the PLL1 tuning voltage crosses the low threshold, DAC Low is asserted. When PLL1 tuning voltage
crosses the high threshold, DAC High is asserted. When either DAC Low or DAC High is asserted, DAC Rail will
also be asserted.
DAC Locked is asserted when EN_Track = 1 and DAC is closely tracking the PLL1 tuning voltage.
8.3.7.5 PLL Divider Outputs
The PLL divider outputs are useful for debugging failure to lock issues. It allows the user to measure the
frequency the PLL inputs are receiving. The settings of PLL1_R, PLL1_N, PLL2_R, and PLL2_N output pulses at
the phase detector rate. The settings of PLL1_R / 2, PLL1_N / 2, PLL2_R / 2, and PLL2_N / 2 output a 50% duty
cycle waveform at half the phase detector rate.
8.3.7.6 CLKinX_LOS
The clock input loss of signal indicator is asserted when LOS is enabled (EN_LOS) and the clock no longer
detects an input as defined by the time-out threshold, LOS_TIMEOUT. The loss of signal indicator detects a loss
of signal on CLKinX only when CLKinX_BUF_TYPE is configured as Bipolar.
8.3.7.7 CLKinX Selected
If this clock is the currently selected/active clock, this pin will be asserted.
8.3.7.8 MICROWIRE Readback
The readback data can be output on any pin programmable to readback mode. For more information on
readback see Readback.
8.3.8 VCO
The integrated VCO uses a frequency calibration routine when register R30 is programmed to lock VCO to target
frequency. Register R30 contains the PLL2_N register.
During the frequency calibration the PLL2_N_CAL value is used instead of PLL2_N, this allows 0-delay modes to
have a separate PLL2 N value for VCO frequency calibration and regular operation.
8.3.9 Clock Distribution
8.3.9.1 Fixed Digital Delay
This section discussing Fixed Digital delay and associated registers is fundamental to understanding digital delay
and dynamic digital delay.
Clock outputs may be delayed or advanced from one another by up to 517.5 clock distribution path periods. By
programming a digital delay value from 4.5 to 522 clock distribution path periods, a relative clock output delay
from 0 to 517.5 periods is achieved. The CLKoutX_DDLY (5 to 522) and CLKoutX_HS (–0.5 or 0) registers set
the digital delay as shown in Table 3.
Table 3. Possible Digital Delay Values
CLKoutX_DDLY CLKoutX_HS Digital Delay
5 1 4.5
5 0 5
6 1 5.5
6 0 6
7 1 6.5
Digital Delay Resolution
(VCO Divider bypassed or external VCO) 1
2 × VCO Frequency
=
Digital Delay Resolution
(with VCO Divider) VCO_DIV
2 × VCO Frequency
=
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Table 3. Possible Digital Delay Values (continued)
CLKoutX_DDLY CLKoutX_HS Digital Delay
7 0 7
... ... ...
520 0 520
521 1 520.5
521 0 521
522 1 521.5
522 0 522
NOTE
Digital delay values only take effect during a SYNC event and if the NO_SYNC_CLKoutX
bit is cleared for this clock output. See Clock Output Synchronization (SYNC) for more
information.
The resolution of digital delay is determined by the frequency of the clock distribution path. The clock distribution
path is the output of Mode Mux1 (Functional Block Diagram). The best resolution of digital delay is achieved by
bypassing the VCO divider.
(2)
(3)
The digital delay between clock outputs can be dynamically adjusted with no or minimum disruption of the output
clocks. See Dynamically Programming Digital Delay for more information.
8.3.9.2 Fixed Digital Delay - Example
Given a VCO frequency of 2457.6 MHz and no VCO divider, by using digital delay the outputs can be adjusted in
1 / (2 × 2457.6 MHz) = approximately 203.5-ps steps.
To achieve quadrature (90 degree shift) between the 122.88-MHz outputs on CLKout4 and CLKout3 from a VCO
frequency of 2457.6 MHz and bypassing the VCO divider, consider the following:
1. The frequency of 122.88 MHz has a period of ~8.14 ns.
2. To delay 90 degrees of a 122.88 MHz clock period requires an approximately 2.03-ns delay.
3. Given a digital delay step of ~203.5 ps, this requires a digital delay value of 12 steps (2.03 ns / 20.35 ps =
10).
4. Since the 10 steps are half period steps, CLKout3_DDLY is programmed 5 full periods beyond 5 for a total of
10.
This result in the following programming:
Clock output dividers to 20. CLKout2_DIV = 20 and CLKout3_DIV = 20.
Set first clock digital delay value. CLKout2_DDLY = 5, CLKout2_HS = 0.
Set second 90 degree shifted clock digital delay value. CLKout3_DDLY = 10, CLKout3_HS = 0.
Table 4 shows some of the possible phase delays in degrees achievable in the above example.
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Table 4. Relative Phase Shift from
CLKout2 to CLKout3
CLKout3_DDLY = 5 and CLKout3_HS = 0
CLKout3_DDLY CLKout_HS RELATIVE DIGITAL DELAY DEGREES of 122.88 MHz
5 1 –0.5 –9°
5 0 0
6 1 0.5
6 0 1 18°
7 1 1.5 27°
7 0 2 36°
8 1 2.5 45°
8 0 3 54°
9 1 3.5 63°
9 0 4 72°
10 1 4.5 81°
10 0 5 90°
11 1 5.5 99°
11 0 6 108°
12 1 6.5 117°
12 0 7 126°
13 1 7.5 135°
13 0 8 144°
14 1 8.5 153°
Figure 12 illustrates clock outputs programmed with different digital delay values during a SYNC event.
See Dynamically Programming Digital Delay for more information on dynamically adjusting digital delay.
8.3.9.3 Clock Output Synchronization (SYNC)
The purpose of the SYNC function is to synchronize the clock outputs with a fixed and known phase relationship
between each clock output selected for SYNC. SYNC can also be used to hold the outputs in a low or 0 state.
The NO_SYNC_CLKoutX bits can be set to disable synchronization for a clock output.
To enable SYNC, EN_SYNC must be set. See EN_SYNC, Enable Synchronization.
The digital delay value set by CLKoutX_DDLY takes effect only upon a SYNC event. The digital delay due to
CLKoutX_HS takes effect immediately upon programming. See Dynamically Programming Digital Delay for more
information on dynamically changing digital delay.
During a SYNC event, clock outputs driven by the VCO are not synchronized to clock outputs driven by OSCin.
OSCout0 is always driven by OSCin. CLKout3 or 4 may be driven by OSCin depending on the
CLKoutX_OSCin_Sel bit value. While SYNC is asserted, NO_SYNC_CLKoutX operates normally for CLKout3
and 4 under all circumstances. SYNC operates normally for CLKout3 and 4 when driven by VCO.
8.3.9.3.1 Effect of SYNC
When SYNC is asserted, the outputs to be synchronized are held in a logic low state. When SYNC is
unasserted, the clock outputs to be synchronized are activated and will transition to a high state simultaneously
with one another except where different digital delay values have been programmed.
See Dynamically Programming Digital Delay for SYNC functionality when SYNC_QUAL = 1.
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Table 5. Steady State Clock Output Condition
Given Specified Inputs
SYNC_TYPE SYNC_POL
_INV SYNC PIN CLOCK OUTPUT STATE
0,1,2 (Input) 0 0 Active
0,1,2 (Input) 0 1 Low
0,1,2 (Input) 1 0 Low
0,1,2 (Input) 1 1 Active
3, 4, 5, 6 (Output) 0 0 or 1 Active
3, 4, 5, 6 (Output) 1 0 or 1 Low
8.3.9.3.2 Methods of Generating SYNC
There are five methods to generate a SYNC event:
Manual:
Asserting the SYNC pin according to the polarity set by SYNC_POL_INV.
Toggling the SYNC_POL_INV bit though MICROWIRE will cause a SYNC to be asserted.
Automatic:
If PLL1_SYNC_DLD or PLL2_SYNC_DLD is set, the SYNC pin will be asserted while DLD (digital lock
detect) is false for PLL1 or PLL2 respectively.
Programming Register R30, which contains PLL2_N will generate a SYNC event when using the internal
VCO.
Programming Register R0 through R5 when SYNC_EN_AUTO = 1.
NOTE
Due to the speed of the clock distribution path (as fast as approximately 325-ps period)
and the slow slew rate of the SYNC, the exact VCO cycle at which the SYNC is asserted
or unasserted by the SYNC is undefined. The timing diagrams show a sharp transition of
the SYNC to clarify functionality.
8.3.9.3.3 Avoiding Clock Output Interruption Due to SYNC
Any CLKout outputs that have their NO_SYNC_CLKoutX bits set will be unaffected by the SYNC event. It is
possible to perform a SYNC operation with the NO_SYNC_CLKoutX bits cleared, then set the
NO_SYNC_CLKoutX bits so that the selected clocks will not be affected by a future SYNC. Future SYNC events
will not effect these clocks but will still cause the newly synchronized clocks to be re-synchronized using the
currently programmed digital delay values. When this happens, the phase relationship between the first group of
synchronized clocks and the second group of synchronized clocks will be undefined unless the SYNC pulse is
qualified by an output clock. See Dynamically Programming Digital Delay.
8.3.9.3.4 SYNC Timing
When discussing the timing of the SYNC function, one cycle refers to one period of the clock distribution path.
Distribution
Path
SYNC
(SYNC_POL
_INV=1)
CLKout0
CLKout2
CLKout4
A B C D
6 cycles 6 cycles CLKoutX_DDLY &
CLKoutX_HS
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CLKout0_DIV = 0(valid only for external VCO mode)
CLKout2_DIV = 2
CLKout4_DIV = 4
The digital delay for all clock outputs is 5
The digital delay half step for all clock outputs is 0
SYNC_QUAL = 0 (No qualification)
Figure 11. Clock Output Synchronization Using the SYNC Pin (Active Low)
See Figure 11 during this discussion on the timing of SYNC. SYNC must be asserted for greater than one clock
cycle of the clock distribution path to latch the SYNC event. After SYNC is asserted, the SYNC event is latched
on the rising edge of the distribution path clock, at time A. After this event has been latched, the outputs will not
reflect the low state for 6 cycles, at time B. Due to the asynchronous nature of SYNC with respect to the output
clocks, it is possible that a glitch pulse could be created when the clock output goes low from the SYNC event.
This is shown by CLKout4 in Figure 11 and CLKout2 in Figure 12. See Relative Dynamic Digital Delay for more
information on synchronizing relative to an output clock to eliminate or minimize this glitch pulse.
After SYNC becomes unasserted the event is latched on the following rising edge of the distribution path clock,
time C. The clock outputs will rise at time D, coincident with a rising distribution clock edge that occurs after 6
cycles plus as many more cycles as programmed by the digital delay for that clock output. Therefore, the
soonest a clock output will become high is 11 cycles after the SYNC unassertion event registration, time C, when
the smallest digital delay value of 5 is set. If CLKoutX_HS = 1 and CLKoutX_DDLY = 5, then the clock output will
rise 10.5 cycles after SYNC is unassertion event registration.
Distribution
Path
SYNC
(SYNC_POL
_INV=1)
CLKout0
CLKout2
CLKout4
A B C D
CLKout5
E F
6 cycles
6 cycles
CLKoutX_DDLY & CLKoutX_HS
4.5
cycles 2.5
cycles 1 cycle
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CLKout0_DIV = 2, CLKout0_DDLY = 5
CLKout2_DIV = 4, CLKout2_DDLY = 7
CLKout4_DIV = 4, CLKout4_DDLY = 8
CLKout5_DIV = 4, CLKour4_DDLY = 8
CLKout0_HS = 1
CLKout2_HS = 0
CLKout4_HS = 0
CLKout5_HS = 0
SYNC_QUAL = 0 (No qualification)
Figure 12. Clock Output Synchronization Using the SYNC Pin (Active Low)
Figure 12 illustrates the timing with different digital delays programmed.
Time A) SYNC assertion event is latched.
Time B) SYNC unassertion latched.
Time C) All outputs toggle and remain low. A glitch pulse can occur at this time as shown by CLKout2.
Time D) After 6 + 4.5 = 10.5 cycles CLKout0 rises. This is the shortest time from SYNC unassertion
registration to clock rising edge possible.
Time E) After 6 + 7 = 13 cycles CLKout2 rises. CLKout2 and CLKout4, 5 are programmed for quadrature
operation.
Time F) After 6 + 8 = 14 cycles CLKout4 and 5 rise.
8.3.9.4 Dynamically Programming Digital Delay
To use dynamic digital delay synchronization qualification set SYNC_QUAL = 1. This causes the SYNC pulse to
be qualified by a clock output so that the SYNC event occurs after a specified time from a clock output transition.
This allows the relative adjustment of clock output phase in real-time with no or minimum interruption of clock
outputs. Hence the term dynamic digital delay.
Note that changing the phase of a clock output requires momentarily altering in the rate of change of the clock
output phase and therefore by definition results in a frequency distortion of the signal.
Without qualifying the SYNC with an output clock, the newly synchronized clocks would have a random and
unknown digital delay (or phase) with respect to clock outputs not currently being synchronized.
8.3.9.4.1 Absolute vs Relative Dynamic Digital Delay
The clock used for qualification of SYNC is selected with the feedback mux (FEEDBACK_MUX).
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If the clock selected by the feedback mux has its NO_SYNC_CLKoutX = 1, then an absolute dynamic digital
delay adjustment will be performed during a SYNC event and the digital delay of the feedback clock will not be
adjusted.
If the clock selected by the feedback mux has its NO_SYNC_CLKoutX = 0, then a self-referenced or relative
dynamic digital delay adjustment will be performed during a SYNC event and the digital delay of the feedback
clock will be adjusted.
Clocks with NO_SYNC_CLKoutX = 1 always operate without interruption.
8.3.9.4.2 Dynamic Digital Delay and 0-Delay Mode
When using a 0-delay mode absolute dynamic digital delay is recommended. Using relative dynamic digital
delay with a 0-delay mode may result in a momentary clock loss on the adjusted clock also being used for 0-
delay feedback that may result in PLL1 DLD becoming low. This may result in HOLDOVER mode being activated
depending upon device configuration.
8.3.9.4.3 SYNC and Minimum Step Size
The minimum step size adjustment for digital delay is half a clock distribution path cycle. This is achieved by
using the CLKoutX_HS bit. The CLKoutX_HS bit change effect is immediate without the need for SYNC. To shift
digital delay using CLKoutX_DDLY a SYNC signal must be generated for the change to take effect.
8.3.9.4.4 Programming Overview
To dynamically adjust the digital delay with respect to an existing clock output the device should be programmed
as follows:
Set SYNC_QUAL = 1 for clock output qualification.
Set CLKout2_PD = 0. Required for proper operation of SYNC_QUAL = 1.
Set EN_FEEDBACK_MUX = 1 to enable the feedback buffer.
Set FEEDBACK_MUX to the clock output that the newly synchronized clocks will be qualified by.
Set NO_SYNC_CLKoutX = 1 for the output clocks that will continue to operate during the SYNC event. There
is no interruption of output on these clocks.
If FEEDBACK_MUX selects a clock output with NO_SYNC_CLKoutX = 1, then absolute dynamic digital
delay is performed.
If FEEDBACK_MUX selects a clock output with NO_SYNC_CLKoutX = 0, then self-referenced or relative
dynamic digital delay is performed.
The SYNC_EN_AUTO bit may be set to cause a SYNC event to begin when register R0 to R5 is
programmed. The auto SYNC feature is a convenience since does not require the application to manually
assert SYNC by toggling the SYNC_POL_INV bit or the SYNC pin when changing digital delay. However,
under the following condition a special programming sequence is required if SYNC_EN_AUTO = 1:
The CLKoutX_DDLY value being set in the programmed register is 13 or more.
Under the following condition a SYNC_EN_AUTO must = 0:
If the application requires a digital delay resolution of half a clock distribution path cycle in relative
dynamic digital delay mode because the HS bit must be fixed per Table 6 for a qualifying clock.
8.3.9.4.5 Internal Dynamic Digital Delay Timing
To dynamically adjust digital delay a SYNC must occur. Once the SYNC is qualified by an output clock, 3 cycles
later an internal one shot pulse will occur. The width of the one shot pulse is 3 cycles. This internal one shot
pulse will cause the outputs to turn off and then back on with a fixed delay with respect to the falling edge of the
qualification clock. This allows for dynamic adjustments of digital delay with respect to an output clock.
The qualified SYNC timing is shown in Figure 13 for absolute dynamic digital delay and Figure 14 for relative
dynamic digital delay.
8.3.9.4.6 Other Timing Requirements
When adjusting digital delay dynamically, the falling edge of the qualifying clock selected by the
FEEDBACK_MUX must coincide with the falling edge of the clock distribution path. For this requirement to be
met, program the CLKoutX_HS value of the qualifying clock output according to Table 6.
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Table 6. Half Step Programming Requirement of Qualifying Clock During SYNC Event
DISTRIBUTION PATH FREQUENCY CLKoutX_DIV value CLKoutX_HS
1.8 GHz Even Must = 1 during SYNC event.
Odd Must = 0 during SYNC event.
< 1.8 GHz Even Must = 0 during SYNC event.
Odd Must = 1 during SYNC event.
8.3.9.5 Absolute Dynamic Digital Delay
Absolute dynamic digital delay can be used to program a clock output to a specific phase offset from another
clock output.
Pros:
Simple direct phase adjustment with respect to another clock output.
CLKoutX_HS will remain constant for qualifying clock.
Can easily use auto sync feature (SYNC_EN_AUTO = 1) when digital delay adjustment requires half step
digital delay requirements.
Can be used with 0-delay mode.
Cons:
For some phase adjustments there may be a glitch pulse due to SYNC assertion.
For example see CLKout4 in Figure 11 and CLKout2 in Figure 12.
8.3.9.5.1 Absolute Dynamic Digital Delay - Example
To illustrate the absolute dynamic digital delay adjust procedure, consider the following example.
System Requirements:
VCO Frequency = 2457.6 MHz
CLKout0 = 819.2 MHz (CLKout0_DIV = 3)
CLKout2 = 307.2 MHz (CLKout2_DIV = 8)
CLKout4 = 245.76 MHz (CLKout4_DIV = 10)
For all clock outputs during initial programming:
CLKoutX_DDLY = 5
CLKoutX_HS = 1
NO_SYNC_CLKoutX = 0
The application requires the 307.2 MHz clock to be stepped in 22.5 degree steps (approximately 203.4 ps),
which is the minimum step resolution allowable by the clock distribution path requiring use of the half step bit
(CLKoutX_HS). That is 1 / 2457.6 MHz / 2 = ~203.4 ps. During the stepping of the 307.2 MHz clock the 819.2
MHz and 245.76 MHz clock must not be interrupted.
1. The device is programmed from register R0 to R30 with values that result in the device being locked and
operating as desired, see the system requirements above. The phase of all the output clocks are aligned
because all the digital delay and half step values were the same when the SYNC was generated by
programming register R30. The timing of this is as shown in Figure 11.
2. Now the registers will be programmed to prepare for changing digital delay (or phase) dynamically.
Table 7. Register Setup for Absolute Dynamic Digital Delay Example
REGISTER PURPOSE
SYNC_QUAL = 1 Use a clock output for qualifying the SYNC pulse for dynamically
adjusting digital delay.
EN_SYNC = 1 (default) Required for SYNC functionality.
CLKout2_PD = 0 Required when SYNC_QUAL = 1.
CLKout2 outputs may be powered down or in use.
EN_FEEDBACK_MUX = 1 Enable the feedback mux for SYNC operation for dynamically
adjusting digital delay.
FEEDBACK_MUX = 2 (CLKout4) Use the fixed 245.76 MHz clock as the SYNC qualification clock.
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Table 7. Register Setup for Absolute Dynamic Digital Delay Example (continued)
REGISTER PURPOSE
NO_SYNC_CLKout0 = 1 This clock output (819.2 MHz) won't be affected by SYNC. It will
always operate without interruption.
NO_SYNC_CLKout4 = 1 This clock output (245.76 MHz) won't be affected by SYNC. It will
always operate without interruption.
This clock will also be the qualifying clock in this example.
CLKout4_HS = 1 Since CLKout4 is the qualifying clock and CLKoutX_DIV is even, the
half step bit must be set to 1. See Table 6.
SYNC_EN_AUTO = 1 Automatic generation of SYNC is allowed for this case.
After the registers in Table 7 have been programmed, the application may now dynamically adjust the digital
delay of CLKout2 (307.2 MHz).
3. Adjust digital delay of CLKout2.
See Table 8 for the programming values to set a specified phase offset from the absolute reference clock.
Table 8 is dependant upon the qualifying clock divide value of 12, see Calculating Dynamic Digital Delay Values
For Any Divide for information on creating tables for any divide value.
Table 8. Programming for Absolute Digital Delay Adjustment
DEGREES OF ADJUSTMENT FROM INITIAL 307.2-MHZ PHASE PROGRAMMING
±0 or ±360 degrees CLKout2_DDLY = 14; CLKout2_HS = 1
22.5° –337.5° CLKout2_DDLY = 14; CLKout2_HS = 0
45° –315° CLKout2_DDLY = 15; CLKout2_HS = 1
67.5° –292.54° CLKout2_DDLY = 5; CLKout2_HS = 0
90° –270° CLKout2_DDLY = 6; CLKout2_HS = 1
112.5° –247.5° CLKout2_DDLY = 6; CLKout2_HS = 0
135° –25° CLKout2_DDLY = 7; CLKout2_HS = 1
157.5° –202.5° CLKout2_DDLY = 7; CLKout2_HS = 0
180° –180° CLKout2_DDLY = 8; CLKout2_HS = 1
247.5° –112.5° CLKout2_DDLY = 8; CLKout2_HS = 0
270° –90° CLKout2_DDLY = 9; CLKout2_HS = 1
292.5° –67.5° CLKout2_DDLY = 9; CLKout2_HS = 0
315° –45° CLKout2_DDLY = 10; CLKout2_HS = 1
337.5° –22.5° CLKout2_DDLY = 10; CLKout2_HS = 0
After setting the new digital delay values, the act of programming R1 will start a SYNC automatically because
SYNC_EN_AUTO = 1.
If the user elects to reduce the number of SYNCs because they are not required when only CLKout2_HS is set,
then SYNC_EN_AUTO is = 0 and the SYNC may now be generated by toggling the SYNC pin or by toggling the
SYNC_POL_INV bit. Because of the internal one shot pulse, no strict timing of the SYNC pin or SYNC_POL_INV
bit is required.
After the SYNC event, the clock output will adjust according to Table 8. See Figure 13 for a detailed view of the
timing diagram. The timing diagram critical points are:
Time A) SYNC assertion event is latched.
Time B) First qualifying falling clock output edge.
Time C) Second qualifying falling clock output edge.
Time D) Internal one shot pulse begins. 5 cycles later clock outputs will be forced low
Time E) Internal one shot pulse ends. 5.5 cycles + digital delay cycles later the synced clock outputs rise.
Time F) Clock outputs are forced low. (CLKout2 is already low).
Time G) Beginning of digital delay cycles.
Time H) For CLKout2_DDLY = 14; the clock output rises now.
Distribution
Path
Internal One
Shot Pulse
5 cycles CLKoutX_DDLY and CLKoutX_HS
3 cycles
SYNC
5.5 cycles
AB C D E F G
CLKout0 /3
HS = 1
CLKout2 /8
HS = 1
CLKout4 /10
HS = 1
3 cycles
H
13.5 cycles
2
1
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(SYNC_QUAL = 1, Qualify with clock output)
Figure 13. Absolute Dynamic Digital Delay Programming Example
8.3.9.6 Relative Dynamic Digital Delay
Relative dynamic digital delay can be used to program a clock output to a specific phase offset from another
clock output.
Pros:
Simple direct phase adjustment with respect to same clock output.
The clock output will always behave the same during digital delay adjustment transient. For some divide
values there will be no glitch pulse.
Cons:
For some clock divide values there may be a glitch pulse due to SYNC assertion.
Adjustments of digital delay requiring the half step bit (CLKoutX_HS) for finer digital delay adjust is
complicated.
Use with 0-delay mode may result in PLL1 DLD becoming low and HOLDOVER mode becoming activated.
DISABLE_DLD1_DET can be set to prevent HOLDOVER from becoming activated due to PLL1 DLD
becoming low.
8.3.9.6.1 Relative Dynamic Digital Delay - Example
To illustrate the relative dynamic digital delay adjust procedure, consider the following example.
System Requirements:
VCO Frequency = 2457.6 MHz
CLKout0 = 819.2 MHz (CLKout0_DIV = 3)
CLKout2 = 491.52 MHz (CLKout2_DIV = 5)
CLKout4 = 491.52 MHz (CLKout4_DIV = 5)
For all clock outputs during initial programming:
CLKoutX_DDLY = 5
CLKoutX_HS = 0
NO_SYNC_CLKoutX = 0
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The application requires the 491.52 MHz clock to be stepped in 22.5degree steps (~203.4 ps), which is the
minimum step resolution allowable by the clock distribution path. That is 1 / 2457.62 MHz / 2 = ~203.4 ps. During
the stepping of the 491.52 MHz clocks the 819.2 MHz clock must not be interrupted.
1. The device is programmed from register R0 to R30 with values that result in the device being locked and
operating as desired, see the system requirements above. The phase of all the output clocks are aligned
because all the digital delay and half step values were the same when the SYNC was generated by
programming register R30. The timing of this is as shown in Figure 11.
2. Now the registers will be programmed to prepare for changing digital delay (or phase) dynamically.
Table 9. Register Setup for Relative Dynamic Digital Delay Adjustment
REGISTER PURPOSE
SYNC_QUAL = 1 Use clock output for qualifying the SYNC pulse for dynamically
adjusting digital delay.
EN_SYNC = 1 (default) Required for SYNC functionality.
CLKout2_PD = 0 Required when SYNC_QUAL = 1.
CLKout2 outputs may be powered down or in use.
EN_FEEDBACK_MUX = 1 Enable the feedback mux for SYNC operation for dynamically
adjusting digital delay.
FEEDBACK_MUX = 1 (CLKout2) Use the clock itself as the SYNC qualification clock.
NO_SYNC_CLKout0 = 1 This clock output (819.2 MHz) won't be affected by SYNC. It will
always operate without interruption.
NO_SYNC_CLKout4 = 1 CLKout4’s phase is not to change with respect to CLKout0.
SYNC_EN_AUTO = 0 (default) Automatic generation of SYNC is not allowed because of the half
step requirement in relative dynamic digital delay mode.
SYNC must be generated manually by toggling the SYNC_POL_INV
bit or the SYNC pin.
After the above registers have been programmed, the application may now dynamically adjust the digital
delay of the 491.52 MHz clocks.
3. Adjust digital delay of CLKout2 by one step which is 22.5 degrees or approximately 203.4 ps.
See Table 10 for the programming sequence to step one half clock distribution period forward or backwards.
Refer to Calculating Dynamic Digital Delay Values For Any Divide for more information on how to calculate digital
delay and half step values for other cases.
To fulfill the qualifying clock output half step requirement in Table 6 when dynamically adjusting digital delay, the
CLKoutX_HS bit must be cleared for clocks with even divides. So before any dynamic digital delay adjustment,
CLKoutX_HS must be clear because the clock divide value is even. To achieve the final required digital delay
adjustment, the CLKoutX_HS bit may set after SYNC.
Table 10. Programming Sequence for One Step Adjust
STEP DIRECTION AND CURRENT HS STATE PROGRAMMING SEQUENCE
Adjust clock output one step forward.
CLKout2_HS is 0. 1. CLKout2_HS = 1.
Adjust clock output one step forward.
CLKout2_HS is 1. 1. CLKout2_DDLY = 11.
2. Perform SYNC event.
3. CLKout2_HS = 0.
Adjust clock output one step backward.
CLKout2_HS is 0. 1. CLKout2_HS = 1.
2. CLKout2_DDLY =11.
3. Perform SYNC event.
Adjust clock output one step backward.
CLKout2_HS is 1. 1. CLKout2_HS = 0.
After programing the updated CLKout2_DDLY and CLKout2_HS values, perform a SYNC event. The SYNC may
be generated by toggling the SYNC pin or by toggling the SYNC_POL_INV bit. Because of the internal one shot
pulse, no strict timing of the SYNC pin or SYNC_POL_INV bit is required. After the SYNC event, the clock output
will be at the specified phase. See Figure 14 for a detailed view of the timing diagram. The timing diagram critical
points are:
Time A) SYNC assertion event is latched.
Distribution
Path
Internal One
Shot Pulse
5 cycles CLKoutX_DDLY and
CLKoutX_HS
10.5 cycles
3 cycles
SYNC
5.5 cycles
B C D E F G
CLKout0 /3
HS = 1
CLKout2 /5
HS = 1
CLKout4 /5
HS = 1
3 cycles
2
H
A
1
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Time B) First qualifying falling clock output edge.
Time C) Second qualifying falling clock output edge.
Time D) Internal one shot pulse begins. 5 cycles later clock outputs will be forced low.
Time E) Internal one shot pulse ends. 5.5 cycles + digital delay cycles later the synced clock outputs rise.
Time F) Clock outputs are forced low. (CLKouts are already low).
Time G) Beginning of digital delay cycles.
Time H) For CLKout2_DDLY = 11; the clock output rises now.
(SYNC_QUAL = 1, Qualify with clock output)
Starting condition is after half step is removed (CLKout2_HS = 0).
Figure 14. Relative Dynamic Digital Delay Programming Example—2nd Adjust
8.3.10 0-Delay Mode
When 0-delay mode is enabled the clock output selected by the Feedback Mux is connected to the PLL1 N
counter to ensure a fixed phase relationship between the selected CLKin and the fed back CLKout. When all the
clock outputs are synced together, all the clock outputs will share the same fixed phase relationship between the
selected CLKin and the fed back CLKout. The feedback can be internal or external using FBCLKin port.
When 0-delay mode is enabled the lowest frequency clock output is fed back to the Feedback Mux to ensure a
repeatable fixed CLKin to CLKout phase relationship between all clock outputs.
If a clock output that is not the lowest frequency output is selected for feedback, then clocks with lower
frequencies will have an unknown phase relationship with respect the other clocks and clock input. There will be
a number of possible phase relationships equal to Feedback_Clock_Frequency / Lower_Clock_Frequency that
may occur.
The Feedback Mux can select a clock output of some of the clocks for internal feedback or the FBCLKin port for
external 0-delay feedback.
To use 0-delay mode, the bit EN_FEEDBACK_MUX must be set (=1) to power up the feedback mux.
See PLL Programming for more information on programming PLL1_N for 0-delay mode.
When using an external VCO mode, internal 0-delay feedback must be used since the FBCLKin port is shared
with the Fin input.
Table 11 outlines several registers to program for 0-delay mode.
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Table 11. Programming 0-Delay Mode
REGISTER PURPOSE
MODE = 2 or 5 Select one of the 0-delay modes for device.
EN_FEEDBACK_MUX = 1 Enable feedback mux.
FEEDBACK_MUX = Application Specific Select CLKout or FBCLKin for 0-delay feedback.
CLKoutX_DIV The divide value of the clock selected by FEEDBACK_MUX is
important for PLL2 N value calculation
PLL1_N PLL1_N value used with CLKoutX_DIV in loop.
8.3.11 Hitless Switching
The LMK04906 supports hitless switching.
8.4 Device Functional Modes
8.4.1 Mode Selection
The LMK04906 family is capable of operating in several different modes as programmed by MODE: Device
Mode.
Table 12. Device Mode Selection
MODE
R11[31:27] PLL1 PLL2 PLL2 VCO 0-DELAY CLOCK DIST
0 X X Internal X
2 X X Internal X X
3 X X External X
5 X X External X X
6 X Internal X
8 X Internal X X
11 X External X
16 X
In addition to selecting the device's mode of operation above, some modes require additional configuration. Also
there are other features including holdover and dynamic digital delay that can also be enabled.
Table 13. Registers to Further Configure Device Mode of Operation
REGISTER HOLDOVER 0-DELAY DYNAMIC DIGITAL
DELAY
HOLDOVER_MODE 2
EN_TRACK User
DAC_CLK_DIV User
EN_MAN_DAC User
DISABLE_DLD1_DET User
EN_VTUNE_RAIL_
DET User
DAC_HIGH_TRIP User
DAC_LOW_TRIP User
FORCE_HOLDOVER 0
SYNC_EN_AUTO User
SYNC_QUAL 1
EN_SYNC 1
CLKout2_PD 0
EN_
FEEDBACK_MUX 1 1
R
CLKinX
CLKinX*
N
Phase
Detector
PLL1
External VCXO
or Tunable
Crystal
R
N
Phase
Detector
PLL2 Internal
VCO
External
Loop Filter
OSCin
CPout1
OSCout0
OSCout0*
LMK04906
CPout2
Partially
Integrated
Loop Filter
6 outputs
External
Loop Filter
PLL1 PLL2
6 blocks
1 output
3 inputs
Input
Buffer CLKoutX
CLKoutX*
Divider
Digital Delay
Analog Delay
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Table 13. Registers to Further Configure Device Mode of Operation (continued)
REGISTER HOLDOVER 0-DELAY DYNAMIC DIGITAL
DELAY
FEEDBACK_MUX Feedback Clock Qualifying Clock
NO_SYNC_
CLKoutX User
8.4.2 Operating Modes
The LMK04906 is a flexible device that can be configured for many different use cases. The following simplified
block diagrams help show the user the different use cases of the device.
8.4.2.1 Dual PLL
Figure 15 illustrates the typical use case of the LMK04906 in dual loop mode. In dual loop mode the reference to
PLL1 is either CLKin0, CLKin1, or CLKin2. An external VCXO or tunable crystal will be used to provide feedback
for the first PLL and a reference to the second PLL. This first PLL cleans the jitter with the VCXO or low cost
tunable crystal by using a narrow loop bandwidth. The VCXO or tunable crystal output may be buffered through
the OSCout0 port and optionally on up to 2 of the CLKouts. The VCXO or tunable crystal is used as the
reference to PLL2 and may be doubled using the frequency doubler. The internal VCO drives up to six
divide/delay blocks which drive 6 clock outputs.
Holdover functionality is optionally available when the input reference clock is lost. Holdover works by fixing the
tuning voltage of PLL1 to the VCXO or tunable crystal.
It is also possible to use an external VCO in place of PLL2's internal VCO.
Figure 15. Simplified Functional Block Diagram for Dual Loop Mode
8.4.2.2 0-Delay Dual PLL
Figure 16 illustrates the use case of 0-delay dual loop mode. This configuration is very similar to Dual PLL except
that the feedback to the first PLL is driven by a clock output. This causes the clock outputs to have deterministic
phase with the clock input. Since all the clock outputs can be synchronized together, all the clock outputs can be
in phase with the clock input signal. The feedback to PLL1 can be connected internally as shown, or externally
using FBCLKin (CLKin1) as an input port.
It is also possible to use an external VCO in place of PLL2's internal VCO.
R
N
Phase
Detector
PLL2 Internal
VCO
OSCin
OSCout0
OSCout0*
LMK04906
CPout2
Partially
Integrated
Loop Filter 6 outputs
External
Loop Filter
PLL2
6 blocks
1 outputs
OSCin* CLKoutX
CLKoutX*
Divider
Digital Delay
Analog Delay
R
CLKinX
CLKinX*
Phase
Detector
PLL1
External VCXO
or Tunable
Crystal
R
N
Phase
Detector
PLL2 Internal
VCO
External
Loop Filter
Input
Buffer
CPout1
OSCout0
OSCout0*
LMK04906
CPout2
Partially
Integrated
Loop Filter 6 outputs
External
Loop Filter
PLL1 PLL2
6 blocks
1 output
3 inputs
N
OSCin
Internal or external loopback, user programmable
CLKoutX
CLKoutX*
Divider
Digital Delay
Analog Delay
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Figure 16. Simplified Functional Block Diagram for 0-delay Dual Loop Mode
8.4.2.3 Single PLL
Figure 17 illustrates the use case of single PLL mode. In single PLL mode only PLL2 is used and PLL1 is
powered down. OSCin is used as the reference input. The internal VCO drives up to 6 divide/delay blocks which
drive 6 clock outputs. The reference at OSCin can be used to drive the OSCout0 port. OSCin can also optionally
drive up to 2 of the clock outputs.
It is also possible to use an external VCO in place of PLL2's internal VCO.
Figure 17. Simplified Functional Block Diagram for Single Loop Mode
8.4.2.4 0-delay Single PLL
Figure 18 illustrates the use case of 0-delay single PLL mode. This configuration is very similar to Single PLL
except that the feedback to PLL2 comes from a clock output. This causes the clock outputs to be in phase with
the reference input. Since all the clock outputs can be synchronized together, all the clock outputs can be in
phase with the clock input signal. The feedback to PLL2 can be performed internally as shown, or externally
using FBCLKin (CLKin1) as an input port.
It is also possible to use an external VCO in place of PLL2's internal VCO.
CLKin1
CLKin1*
OSCin OSCout0
OSCout0*
LMK04906
OSCin*
6 outputs
6 blocks
1 output
CLKoutX
CLKoutX*
Divider
Digital Delay
Analog Delay
R
N
Phase
Detector
PLL2 Internal
VCO
OSCin
OSCout0
OSCout0*
LMK04906
CPout2
Partially
Integrated
Loop Filter 6 outputs
External
Loop Filter
PLL2
6 blocks
1 output
OSCin*
Internal or external loopback, user programmable
CLKoutX
CLKoutX*
Divider
Digital Delay
Analog Delay
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Figure 18. Simplified Functional Block Diagram for 0-delay Single Loop Mode
8.4.2.5 Clock Distribution
Figure 19 illustrates the LMK04906 used for clock distribution. CLKin1 is used to drive up to 6 divide/delay blocks
which drive 6 outputs. OSCin can be used to drive the OSCout port. OSCin can also optionally drive up to 2 of
the clock outputs.
Figure 19. Simplified Functional Block Diagram for Mode Clock Distribution
8.5 Programming
LMK04906 devices are programmed using 32-bit registers. Each register consists of a 5-bit address field and 27-
bit data field. The address field is formed by bits 0 through 4 (LSBs) and the data field is formed by bits 5 through
31 (MSBs). The contents of each register is clocked in MSB first (bit 31), and the LSB (bit 0) last. During
programming, the LEuWire signal should be held low. The serial data is clocked in on the rising edge of the
CLKuWire signal. After the LSB (bit 0) is clocked in the LEuWire signal should be toggled low-to-high-to-low to
latch the contents into the register selected in the address field. It is recommended to program registers in
numeric order, for example R0 to R16, and R24 to R31 to achieve proper device operation. Figure 6 illustrates
the serial data timing sequence.
To achieve proper frequency calibration, the OSCin port must be driven with a valid signal before programming
register R30. Changes to PLL2 R divider or the OSCin port frequency require register R30 to be reloaded in
order to activate the frequency calibration process.
8.5.1 Special Programming Case for R0 to R5 for CLKoutX_DIV and CLKoutX_DDLY
In some cases when programming register R0 to R5 to change the CLKoutX_DIV divide value or
CLKoutX_DDLY delay value, 3 additional CLKuWire cycles must occur after loading the register for the newly
programmed divide or delay value to take effect. These special cases include:
When CLKoutX_DIV is > 25.
When CLKoutX_DDLY is > 12. Note, loading the digital delay value only prepares for a future SYNC event.
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Programming (continued)
Also, since SYNC_EN_AUTO bit = 1 automatically generates a SYNC on the falling edge of LE when R0 to R5 is
programmed, further programming considerations must be made when SYNC_EN_AUTO = 1.
These special programming cases requiring the additional three clock cycles may be properly programmed by
one of the following methods shown in Table 14.
Table 14. R0 to R5 Special Case
CLKoutX_DIV &
CLKoutX_DDLY
SYNC
_EN_
AUTO PROGRAMMING METHOD
CLKoutX_DIV 25 and
CLKoutX_DDLY 12 0 or 1 No Additional Clocks Required (Normal)
CLKoutX_DIV > 25 or
CLKoutX_DDLY > 12 0Three Extra CLKuWire Clocks (Or program another
register)
CLKoutX_DIV > 25 or
CLKoutX_DDLY > 12 1Three Extra CLKuWire Clocks while LEuWire is
High
Method: No Additional Clocks Required (Normal)
No special consideration to CLKuWire is required when changing divide value to 25, digital delay value to 12,
or when the digital delay and divide value do not change. See MICROWIRE timing Figure 6.
Method: Three Extra CLKuWire Clocks
Three extra clocks must be provided before CLKoutX_DIV > 25 or CLKoutX_DDLY > 12 take effect. See
MICROWIRE timing Figure 7.
Also, by programming another register the three clock requirement can be satisfied.
Method: Three Extra CLKuWire Clocks with LEuWire Asserted
When SYNC_EN_AUTO = 1 the falling edge of LEuWire will generate a SYNC event. CLKoutX_DIV and
CLKoutX_DDLY values must be updated before the SYNC event occurs. So 3 CLKuWire rising edges must
occur before LEuWire goes low. See MICROWIRE timing Figure 8.
Initial Programming Sequence
During the recommended programming sequence the device is programmed in order from R0 to R31, so it is
expected at least one additional register will be programmed after programming the last CLKoutX_DIV or
CLKoutX_DDLY value in R0 to R5. This will result in the extra needed CLKuWire rising edges, so this special
note is of little concern.
If programming R0 to R5 to change CLKout frequency or digital delay or dynamic digital delay at a later time in
the application, care must be taken to provide these extra CLKuWire cycles to properly load the new divide
and/or delay values.
8.5.1.1 Example
In this example, all registers have been programmed, the PLLs are locked. An LMK04906 has been generating a
clock output frequency of 61.44 MHz on CLKout4 using a VCO frequency of 2457.6 MHz and a divide value of
40. SYNC_EN_AUTO = 0. At a later time the application requires a 30.72 MHz output on CLKout4. By
reprogramming register R4 with CLKout4_DIV = 80 twice, the divide value of 80 is set for clock output 4 which
results in an output frequency of 30.72 MHz (2457.6 MHz / 80 = 30.72 MHz) on CLKout4.
In this example the required 3 CLKuWire cycles were achieved by reprogramming the R4 register with the same
value twice.
8.5.2 Recommended Programming Sequence
Registers are programmed in numeric order with R0 being the first and R31 being the last register programmed.
The recommended programming sequence involves programming R0 with the reset bit (b17) set to 1 to ensure
the device is in a default state. If R0 is programmed again, the reset bit must be cleared to 0 during the
programming of R0.
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8.5.2.1 Overview
Program R0 with RESET bit = 1. This ensures that the device is configured with default settings. When
RESET = 1, all other R0 bits are ignored.
If R0 is programmed again during the initial configuration of the device, the RESET bit must be cleared.
R0 through R5: CLKouts.
Program as necessary to configure the clock outputs, CLKout0 to CLKout5 as desired. These registers
configure clock output controls such as powerdown, digital delay and divider value, analog delay select,
and clock source select.
R6 through R8: CLKouts.
Program as necessary to configure the clock outputs, CLKout0 to CLKout5 as desired. These registers
configure the output format for each clock outputs and the analog delay for the clock outputs.
R9: Required programming
Program this register as shown in the register map for proper operation.
R10: OSCouts, VCO divider, and 0-delay.
Enable and configure clock outputs OSCout0/1.
Set and select VCO divider (VCO bypass is recommended).
Set 0-delay feedback source if used.
R11: Part mode, SYNC, and XTAL.
Program to configure the mode of the part, to configure SYNC functionality and pin, and to enable crystal
mode.
R12: Pins, SYNC, and holdover mode.
Status_LD pin, more SYNC options to generate a SYNC upon PLL1 and/or PLL2 lock detect.
Enable clock features such as holdover.
R13: Pins, holdover mode, and CLKins.
Status_HOLDOVER, Status_CLKin0, and Status_CLKin1 pin controls.
Enable clock inputs for use in specific part modes.
R14: Pins, LOS, CLKins, and DAC.
Status_CLKin1 pin control.
Loss of signal detection, CLKin type, DAC rail detect enable and high and low trip points.
R15: DAC and holdover mode.
Program to enable and set the manual DAC value.
HOLDOVER mode options.
R16: Crystal amplitude.
Increasing XTAL_LVL can improve tunable crystal phase noise performance.
R24: PLL1 and PLL2.
PLL1 N and R delay and PLL1 digital lock delay value.
PLL2 integrated loop filter.
R25: DAC and PLL1.
Program to configure DAC update clock divider and PLL1 digital lock detect count.
R26: PLL2.
Program to configure PLL2 options.
R27: CLKins and PLL1.
Clock input pre-dividers.
Program to configure PLL1 options.
R28: PLL1 and PLL2.
Program to configure PLL2 R and PLL1 N.
R29: OSCin and PLL2.
Program to configure oscillator input frequency, PLL2 fast phase detector frequency mode, and PLL2 N
calibration value.
R30: PLL2.
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Program to configure PLL2 prescaler and PLL2 N value.
R31: uWire lock.
Program to set the uWire_LOCK bit.
8.5.3 Readback
At no time should the MICROWIRE registers be programmed to any value other than what is specified in the
datasheet.
For debug of the MICROWIRE interface, it is recommended to simply program an output pin mux to active low
and then toggle the output type register between output and inverting output while observing the output pin for a
low to high transition. For example, to verify MICROWIRE programming, set the LD_MUX = 0 (Low) and then
toggle the LD_TYPE register between 3 (Output, push-pull) and 4 (Output inverted, push-pull). The result will be
that the Status_LD pin will toggle from low to high.
Readback from the MICROWIRE programming registers is available. The MICROWIRE readback function can
be enabled on the Status_LD, Status_HOLDOVER, Status_CLKin0, Status_CLKin1, or SYNC pin by
programming the corresponding MUX register to “uWire Readback” and the corresponding TYPE register to
"Output (push-pull)." Power on reset defaults the Status_HOLDOVER pin to “uWire Readback.”
Figure 9 illustrates the serial data timing sequence for a readback operation for both cases of READBACK_LE =
0 (POR default) and READBACK_LE = 1.
To perform a readback operation first set the register to be read back by programming the READBACK_ADDR
register. Then after any MICROWIRE write operation, with the LEuWire pin held low continue to clock the
CLKuWire pin. On every rising edge of the CLKuWire pin a new data bit is clocked onto the any pins
programmed for uWire Readback. If the READBACK_LE bit is set, the LEuWire pin should be left high after
LEuWire rising edge while continuing to clock the CLKuWire pin.
It is allowable to perform a register read back in the same MICROWIRE operation which set the
READBACK_ADDR register value.
Data is clocked out MSB first. After 27 clocks all the data values will have been read and the read operation is
complete. If READBACK_LE = 1, the LEuWire line may now be lowered. It is allowable for the CLKuWire pin to
be clocked additional cycles, but the data on the readback pin will be invalid.
CLKuWire must be low before the falling edge of LEuWire.
8.5.3.1 Readback - Example
To readback register R3 perform the following steps:
Write R31 with READBACK_ADDR = 3; READBACK_LE = 0. DATAuWire and CLKuWire are toggled as
shown in Figure 6 with new data being clocked in on rising edges of CLKuWire
Toggle LEuWire high and then low as shown in Figure 6 and Figure 9. LEuWire is returned low because
READBACK_LE = 0.
Toggle CLKuWire high and then low 27 times to read back all 27 bits of register R3. Data is read MSB first.
Data is valid on falling edge of CLKuWire.
Read operation is complete.
8.6 Register Maps
8.6.1 Register Map and Readback Register Map
Table 15 provides the register map for device programming. Normally any register can be read from the same
data address it is written to. However, READBACK_LE has a different readback address. Also, the DAC_CNT
register is a read only register. Table 16 shows the address for READBACK_LE and DAC_CNT. Bits marked as
reserved are undefined upon readback.
Observe that only the DATA bits are readback during a readback which can result in an offset of 5 bits between
the two register tables.
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Table 15. Register Map Description
Register 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Data [26:0] Address [4:0]
R0
CLKout 0_PD
0
CLKout0_ ADLY_SEL
0 CLKout0_DDLY [27:18] RESET
CLKout 0_HS
CLKout0_DIV [15:5] 0 0 0 0 0
R1
CLKout 1_PD
0 0
CLKout1_ ADLY_SEL
CLKout1_DDLY [27:18]
POWERDOWN
CLKout 1_HS
CLKout1_DIV [15:5] 0 0 0 0 1
R2
CLKout 2_PD
0
CLKout2_ ADLY_SEL
0 CLKout2_DDLY [27:18] 0
CLKout 2_HS
CLKout2_DIV [15:5] 0 0 0 1 0
R3
CLKout 3_PD
CLKout3_ OSCin_Sel
0
CLKout3_ ADLY_SEL
CLKout3_DDLY [27:18] 0
CLKout 3_HS
CLKout3_DiV [15:5] 0 0 0 1 1
R4
CLKout 4_PD
C0LKout4_ OSCin_Sel
0
CLKout4_ ADLY_SEL
CLKout4_DDLY [27:18] 0
CLKout 4_HS
CLKout4_DIV [15:5] 0 0 1 0 0
R5
CLKout 5_PD
0 0
CLKout5 ADLY_SEL
CLKout5_DDLY [27:18] 0
CLKout 5_HS
CLKout5_DIV [15:5] 0 0 1 0 1
R6 0 CLKout1_TYPE [27:24] CLKout0_TYPE [23:20] 0 CLKout1_ADLY
[15:11] 0CLKout0_ADLY
[9:5] 00110
R7 0 CLKout3_TYPE [27:24] CLKout2_TYPE [23:20] 0 CLKout3_ADLY
[15:11] 0CLKout2_ADLY
[9:5] 00111
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Table 15. Register Map Description (continued)
Register 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Data [26:0] Address [4:0]
(1) Although the value of 0 is written here, during readback the value of READBACK_LE will be read at this location. See Register Map and Readback Register Map.
R8 0 CLKout5_TYPE [27:24] 0 CLKout4_TYPE [19:16] CLKout5_ADLY
[15:11] 0CLKout4_ADLY
[9:5] 01000
R9 0 10101010101010101010101010 01001
R10 0 0 0 1OSCout0_TYPE [27:24] 0
EN_OSCout0
0
OSCout0_MUX
PD_OSCin
OSCout_DIV
[18:16] 010
VCO_MUX
EN_ FEEDBACK_MUX
VCO_DIV
[10:8] FEEDBACK
_MUX [7:5] 01010
R11 MODE [31:27]
EN_SYNC
NO_SYNC_CLKout5
NO_SYNC_CLKout4
NO_SYNC_CLKout3
NO_SYNC_CLKout2
NO_SYNC_CLKout1
NO_SYNC_CLKout0
SYNC _CLKin2_ MUX [19:18]
SYNC_QUAL
SYNC_POL_INV
SYNC_EN_AUTO
SYNC
_TYPE
[14:12] 000000
EN_PLL2_XTAL
01011
R12 LD_MUX [31:27] LD_TYPE [26:24]
SYNC_PLL2 _DLD
SYNC_PLL1 _DLD
0
(1) 01 1 0 0 0000000
EN_TRACK
HOLDOVER _MODE [7:6]
1 01100
R13 HOLDOVER_MUX
[31:27]
HOLDOVER
_TYPE
[26:24] 0
Status_
CLKin1
_MUX
[22:20]
0
Status_
CLKin0
_TYPE
[18:16]
DISABLE_ DLD1_DET
Status_
CLKin0
_MUX
[14:12]
CLKin
_Select
_MODE
[11:8]
CLKin_Sel_INV
EN_CLKin2
EN_CLKin1
EN_CLKin0
01101
R14
LOS_ TIMEOUT [31:30]
0
EN_LOS
0
Status_
CLKin1
_TYPE
[26:24]
0
CLKin2_BUF_TYPE
CLKin1_BUF_TYPE
CLKin0_BUF_TYPE
DAC_HIGH_TRIP
[19:14] 0 0 DAC_LOW_TRIP
[11:6]
EN_VTUNE_ RAIL_DET
01110
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Table 15. Register Map Description (continued)
Register 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Data [26:0] Address [4:0]
R15 MAN_DAC
[31:22] 0
EN_MAN_DAC
HOLDOVER_DLD_CNT
[19:6]
FORCE_ HOLDOVER
01111
R16 XTAL_
LVL 0 0 0001010101010000010 0 0 0 0 1 0 0 0 0
R24 PLL2_C4_LF
[31:28] PLL2_C3_LF
[27:24] 0PLL2_R4_LF
[22:20] 0PLL2_R3_LF
[18:16] 0PLL1_N_DLY
[14:12] 0PLL1_R_DLY
[10:8]
PLL1_
WND_
SIZE 0 11000
R25 DAC_CLK_DIV [31:22] 0 0 PLL1_DLD_CNT [19:6] 0 1 1 0 0 1
R26 PLL2_
WND_SIZE
[31:30]
EN_PLL2_ REF_2X
PLL2_ CP_POL
PLL2_CP _GAIN [27:26]
111010PLL2_DLD_CNT
[19:6]
PLL2_CP_TRI
11010
R27 0 0 0
PLL1_CP_POL
PLL1_CP_GAIN
CLKin2_ PreR_DIV
CLKin1_ PreR_DIV
CLKin0_ PreR_DIV
PLL1_R
[19:6]
PLL1_CP_TRI
11011
R28 PLL2_R PLL1_N [19:6] 0 1 1 1 0 0
R29 0 0 0 0 0 OSCin_FREQ
[26:24]
PLL2_ FAST_PDF
PLL2_N_CAL [22:5] 1 1 1 0 1
R30 0 0 0 0 0 PLL2_P 0 PLL2_N [22:5] 1 1 1 1 0
R31 0 0 0 0 0 0 0 0 0 0
READBACK _LE
READBACK_ADDR [20:16] 0 0 0 0 0 0 0 0 0 0
uWire_LOCK
11111
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Table 16. Readback Register Map
Register RD
26 RD
25 RD
24 RD
23 RD
22 RD
21 RD
20 RD
19 RD
18 RD
17 RD
16 RD
15 RD
14 RD
13 RD
12 RD
11 RD
10 RD
9RD
8RD
7RD
6RD
5RD
4RD
3RD
2RD
1RD
0
Data [26:0]
RD
R12 LD_MUX [26:22] LD_TYPE
[21:19]
SYNC_PLL2_DLD
SYNC_PLL1_DLD
READBACK_LE
01 1 0 0 0 0 0 0 0 0 0
EN_TRACK
HOLDOVER_MODE [2:1]
1
RD
R23 RESERVED
[26:24] DAC_CNT [23:14] RESERVED [13:0]
RD
R31 RESERVED [26:10]
uWire_LOCK
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8.6.2 Default Device Register Settings After Power On Reset
Table 17 illustrates the default register settings programmed in silicon for the LMK04906 after power on or
asserting the reset bit. Capital X and Y represent numeric values.
Table 17. Default Device Register Settings After Power On Reset
GROUP FIELD NAME DEFAULT
VALUE
(DECIMAL) DEFAULT STATE FIELD DESCRIPTION REGISTER BIT
LOCATION
(MSB:LSB)
Clock Output
Control
CLKout0_PD 1 PD
Powerdown control for analog and digital delay,
divider, and both output buffers
R0
31
CLKout1_PD 1 PD R1
CLKout2_PD 1 PD R2
CLKout3_PD 0 Normal R3
CLKout4_PD 0 Normal R4
CLKout5_PD 1 PD R5
CLKout3_OSCin_Sel 1 OSCin Selects the clock source for a clock output from
internal VCO or external OSCin R3 30
CLKout4_OSCin_Sel 0 VCO R4 30
CLKoutX_ADLY_SEL 0 None Add analog delay for clock output R0 to R5 28, 29
CLKoutX_DDLY 0 5 Digital delay value R0 to R5 27:18 [10]
RESET 0 Not in reset Performs power on reset for device R0 17
POWERDOWN 0 Disabled
(device is active) Device power down control R1 17
CLKoutX_HS 0 No shift Half shift for digital delay R0 to R5 16
CLKout0_DIV 25 Divide-by-25
Divide for clock outputs
R0
15:5 [11]
CLKout1_DIV 25 Divide-by-25 R1
CLKout2_DIV 25 Divide-by-25 R2
CLKout3_DIV 1 Divide-by-1 R3
CLKout4_DIV 25 Divide-by-25 R4
CLKout5_DIV 25 Divide-by-25 R5
CLKout1_TYPE 0 Powerdown
Individual clock output format. Select from
LVDS/LVPECL/LVCMOS.
R6
27:24 [4]CLKout3_TYPE 8 LVCMOS
(Norm/Norm) R7
CLKout5_TYPE 0 Powerdown R8
CLKout0_TYPE 0 Powerdown R6 23:20 [4]
CLKout2_TYPE 0 Powerdown R7
CLKout4_TYPE 1 LVDS R8 19:16 [4]
CLKoutX_ADLY 0 No delay Analog delay setting for clock output R6 to R8 15:11, 9:5 [5]
OSCout0_TYPE 1 LVDS OSCout0 default clock output R10 27:24 [4]
EN_OSCout0 1 Enabled Enable OSCout0 output buffer R10 22
OSCout0_MUX 0 Bypass Divider Select OSCout divider for OSCout0 or bypass R10 20
PD_OSCin 0 OSCin powered Allows OSCin to be powered down. For use in clock
distribution mode. R10 19
OSCout_DIV 0 Divide-by-8 OSCout divider value R10 18:16 [3]
Mode
VCO_MUX 0 VCO Select VCO or VCO Divider output R10 12
EN_FEEDBACK_MUX 0 Disabled Feedback MUX is powered down. R10 11
VCO_DIV 2 Divide-by-2 VCO Divide value R10 10:8 [3]
FEEDBACK_MUX 0 CLKout0 Selects CLKout to feedback into the PLL1 N divider R10 7:5 [3]
MODE 0 Internal VCO Device mode R11 31:27 [5]
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Table 17. Default Device Register Settings After Power On Reset (continued)
GROUP FIELD NAME DEFAULT
VALUE
(DECIMAL) DEFAULT STATE FIELD DESCRIPTION REGISTER BIT
LOCATION
(MSB:LSB)
Clock
Synchronization
EN_SYNC 1 Enabled Enables synchronization circuitry. R11 26
NO_SYNC_CLKout5 0 Will sync
Disable individual clock output from becoming
synchronized.
R11 25
NO_SYNC_CLKout4 1 Will not sync R11 24
NO_SYNC_CLKout3 1 Will not sync R11 23
NO_SYNC_CLKout2 0 Will sync R11 22
NO_SYNC_CLKout1 0 Will sync R11 21
NO_SYNC_CLKout0 0 Will sync R11 20
SYNC_CLKin2_MUX 0 Logic Low Mux controlling SYNC pin when set to output R11 19:18 [2]
SYNC_QUAL 0 Not qualified Allows SYNC operations to be qualified by a clock
output. R11 17
SYNC_POL_INV 1 Logic Low Sets the polarity of the SYNC pin when input R11 16
SYNC_EN_AUTO 0 Manual SYNC is not started by programming a register R0 to
R5. R11 15
SYNC_TYPE 1 Input /w
Pull-up SYNC IO pin type R11 14:12 [3]
Other Mode
Control
EN_PLL2_XTAL 0 Disabled Enable Crystal oscillator for OSCin R11 5
LD_MUX 3 PLL1 & 2 DLD Lock detect mux selection when output R12 31:27 [5]
LD_TYPE 3 Output
(Push-Pull) LD IO pin type R12 26:24 [3]
SYNC_PLL2_DLD 0 Normal Force synchronization mode until PLL2 locks R12 23
SYNC_PLL1_DLD 0 Normal Force synchronization mode until PLL1 locks R12 22
EN_TRACK 1 Enable Tracking DAC tracking of the PLL1 tuning voltage R12 8
HOLDOVER_MODE 2 Enable Holdover Causes holdover to activate when lock is lost R12 7:6 [2]
HOLDOVER_MUX 7 uWire Readback Holdover mux selection R13 31:27 [5]
HOLDOVER_TYPE 3 Output
(Push-Pull) HOLDOVER IO pin type R13 26:24 [3]
Status_CLKin1_MUX 0 Logic Low Status_CLKin1 pin MUX selection R13 22:20 [3]
Status_CLKin0_TYPE 2 Input /w Pull-down Status_CLKin0 IO pin type R13 18:16 [3]
DISABLE_DLD1_DET 0 Not Disabled Disables PLL1 DLD falling edge from causing
HOLDOVER mode to be entered R13 15
Status_CLKin0_MUX 0 Logic Low Status_CLKin0 pin MUX selection R13 14:12 [3]
CLKin_SELECT_MODE 3 Manual Select Mode to use in determining reference CLKin for PLL1 R13 11:9 [3]
CLKin_Sel_INV 0 Active High Invert Status 0 and 1 pin polarity for input R13 8
CLKin Control
EN_CLKin2 1 Usable Set CLKin2 to be usable R13 7
EN_CLKin1 1 Usable Set CLKin1 to be usable R13 6
EN_CLKin0 1 Usable Set CLKin0 to be usable R13 5
LOS_TIMEOUT 0 1200 ns, 420 kHz Time until no activity on CLKin asserts LOS R14 31:30 [2]
EN_LOS 1 Enabled Loss of Signal Detect at CLKin R14 28
Status_CLKin1_TYPE 2 Input /w Pull-down Status_CLKin1 pin IO pin type R14 26:24 [3]
CLKin2_BUF_TYPE 0 Bipolar CLKin2 Buffer Type R14 22
CLKin1_BUF_TYPE 0 Bipolar CLKin1 Buffer Type R14 21
CLKin0_BUF_TYPE 0 Bipolar CLKin0 Buffer Type R14 20
DAC Control
DAC_HIGH_TRIP 0 ~50 mV from Vcc Voltage from Vcc at which holdover mode is entered if
EN_VTUNE_RAIL_DAC is enabled. R14 19:14 [6]
DAC_LOW_TRIP 0 ~50 mV from GND Voltage from GND at which holdover mode is entered
if EN_VTUNE_RAIL_DAC is enabled. R14 11:6 [6]
EN_VTUNE_RAIL_DET 0 Disabled Enable PLL1 unlock state when DAC trip points are
achieved R14 5
MAN_DAC 512 3 V / 2 Writing to this register will set the value for DAC when
in manual override.
Readback from this register is DAC value. R15 31:22 [10]
EN_MAN_DAC 0 Disabled Set manual DAC override R15 20
HOLDOVER_DLD_CNT 512 512 counts Lock must be valid n many clocks of PLL1 PDF
before holdover mode is exited. R15 19:6 [14]
FORCE_HOLDOVER 0 Holdover not forced Forces holdover mode. R15 5
XTAL_LVL 0 1.65 Vpp Sets drive power level of Crystal R16 31:30 [2]
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Table 17. Default Device Register Settings After Power On Reset (continued)
GROUP FIELD NAME DEFAULT
VALUE
(DECIMAL) DEFAULT STATE FIELD DESCRIPTION REGISTER BIT
LOCATION
(MSB:LSB)
(1) This register must be reprogrammed to a value of 2 (3.7 ns) during user programming.
PLL Control
PLL2_C4_LF 0 10 pF PLL2 integrated capacitor C4 value R24 31:28 [4]
PLL2_C3_LF 0 10 pF PLL2 integrated capacitor C3 value R24 27:24 [4]
PLL2_R4_LF 0 200 ΩPLL2 integrated resistor R4 value R24 22:20 [3]
PLL2_R3_LF 0 200 ΩPLL2 integrated resistor R3 value R24 18:16 [3]
PLL1_N_DLY 0 No delay Delay in PLL1 feedback path to decrease lag from
input to output R24 14:12 [3]
PLL1_R_DLY 0 No delay Delay in PLL1 reference path to increase lag from
input to output R24 10:8 [3]
PLL1_WND_SIZE 3 40 ns Window size used for digital lock detect for PLL1 R24 7:6 [2]
DAC_CLK_DIV 4 Divide-by-4 DAC update clock divisor. Divides PLL1 phase
detector frequency. R25 31:22 [10]
PLL1_DLD_CNT 1024 1024 cycles Lock must be valid n many cycles before LD is
asserted R25 19:6 [14]
PLL2_WND_SIZE 0 Reserved
(1) Window size used for digital lock detect for PLL2 R26 31:30 [2]
EN_PLL2_REF_2X 0 Disabled, 1x Doubles reference frequency of PLL2. R26 29
PLL2_CP_POL 0 Negative Polarity of PLL2 Charge Pump R26 28
PLL2_CP_GAIN 3 3.2 mA PLL2 Charge Pump Gain R26 27:26 [2]
PLL2_DLD_CNT 8192 8192 Counts Number of PDF cycles which phase error must be
within DLD window before LD state is asserted. R26 19:6 [14]
PLL2_CP_TRI 0 Active PLL2 Charge Pump Active R26 5
PLL1_CP_POL 1 Positive Polarity of PLL1 Charge Pump R27 28
PLL1_CP_GAIN 0 100 uA PLL1 Charge Pump Gain R27 27:26 [2]
CLKin2_PreR_DIV 0 Divide-by-1 CLKin2 Pre-R divide value (1, 2, 4, or 8) R27 25:24 [2]
CLKin1_PreR_DIV 0 Divide-by-1 CLKin1 Pre-R divide value (1, 2, 4, or 8) R27 23:22 [2]
CLKin0_PreR_DIV 0 Divide-by-1 CLKin0 Pre-R divide value (1, 2, 4, or 8) R27 21:20 [2]
PLL1_R 96 Divide-by-96 PLL1 R Divider (1 to 16383) R27 19:6 [14]
PLL1_CP_TRI 0 Active PLL1 Charge Pump Active R27 5
PLL2_R 4 Divide-by-4 PLL2 R Divider (1 to 4095) R28 31:20 [12]
PLL1_N 192 Divide-by-192 PLL1 N Divider (1 to 16383) R28 19:6 [14]
OSCin_FREQ 7 448 to 511 MHz OSCin frequency range R29 26:24 [3]
PLL2_FAST_PDF 1 PLL2 PDF > 100 MHz When set, PLL2 PDF of greater than 100 MHz may
be used R29 23
PLL2_N_CAL 48 Divide-by-48 Must be programmed to PLL2_N value. R29 22:5 [18]
PLL2_P 2 Divide-by-2 PLL2 N Divider Prescaler (2 to 8) R30 26:24 [3]
PLL2_N 48 Divide-by-48 PLL2 N Divider (1 to 262143) R30 22:5 [18]
READBACK_LE 0 LEuWire Low for Readback State LEuWire pin must be in for readback R31 21
READBACK_ADDR 31 Register 31 Register to read back R31 20:16 [5]
uWire_LOCK 0 Writable The values of registers R0 to R30 are lockable R31 5
8.6.3 Register Descriptions
8.6.3.1 Register R0 to R5
Registers R0 through R5 control the 6 clock outputs CLKout0 to CLKout5. Register R0 controls CLKout0,
Register R1 controls CLKout1, and so on. All functions of the bits in these six registers are identical except the
different registers control different clock outputs. The X in CLKoutX_PD, CLKoutX_ADLY_SEL, CLKoutX_DDLY,
CLKoutX_HS, CLKoutX_DIV denote the actual clock output which may be from 0 to 5.
The RESET bit is only in register R0.
The POWERDOWN bit is only in register R1.
The CLKoutX_OSCin_Sel bit is only in registers R3 and R4.
8.6.3.1.1 CLKoutX_PD, Powerdown CLKoutX Output Path
This bit powers down the clock output as specified by CLKoutX. This includes the divider, digital delay, analog
delay, and output buffers.
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Table 18. CLKoutX_PD
R0-R5[31] STATE
0 Power up clock output
1 Power down clock output
8.6.3.1.2 CLKoutX_OSCin_Sel, Clock Output Source
This bit sets the source for the clock CLKoutX. The selected source will be either from a VCO via Mode Mux1 or
from the OSCin buffer.
This bit is valid only for registers R3 and R4, clock outputs CLKout3 and CLKout4 respectively. All other clock
outputs are driven by a VCO via Mode Mux1.
Table 19. CLKoutX_OSCin_Sel
R3-R4[30] CLOCK OUTPUT SOURCE
0 VCO
1 OSCin
8.6.3.1.3 CLKoutX_ADLX_SEL[29], CLKoutX_ADLX_SEL[28], Select Analog Delay
These bits individually select the analog delay block (CLKoutX_ADLY) for use with CLKoutX. If a clock output
does not use analog delay, the analog delay block is powered down.
Table 20. CLKoutX_ADLX_SEL[29], CLKoutX_ADLX_SEL[28]
R0-R5[28],[29] STATE
0 Analog delay powered down
1 Analog delay on CLKoutX
8.6.3.1.4 CLKoutX_DDLY, Clock Channel Digital Delay
CLKoutX_DDLY and CLKoutX_HS sets the digital delay used for CLKoutX. This value only takes effect during a
SYNC event and if the NO_SYNC_CLKoutX bit is cleared for this clock output. See Clock Output
Synchronization (SYNC).
Programming CLKoutX_DDLY can require special attention. See section Special Programming Case for R0 to
R5 for CLKoutX_DIV and CLKoutX_DDLY for more details.
Using a CLKoutX_DDLY value of 13 or greater will cause the clock output to operate in extended mode
regardless of the clock ouptut's divide value or the half step value.
One clock cycle is equal to the period of the clock distribution path. The period of the clock distribution path is
equal to VCO Divider value divided by the frequency of the VCO. If the VCO divider is disabled or an external
VCO is used, the VCO divide value is treated as 1.
tclock distribution path = VCO divide value / fVCO
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Table 21. CLKoutX_DDLY, 10 Bits
R0-R5[27:18] DELAY POWER MODE
0 (0x00) 5 clock cycles
Normal Mode
1 (0x01) 5 clock cycles
2 (0x02) 5 clock cycles
3 (0x03) 5 clock cycles
4 (0x04) 5 clock cycles
5 (0x05) 5 clock cycles
6 (0x06) 6 clock cycles
7 (0x07) 7 clock cycles
... ...
12 (0x0C) 12 clock cycles
13 (0x0D) 13 clock cycles
Extended Mode
... ...
520 (0x208) 520 clock cycles
521 (0x209) 521 clock cycles
522 (0x20A) 522 clock cycles
8.6.3.1.5 Reset
The RESET bit is located in register R0 only. Setting this bit will cause the silicon default values to be loaded.
When programming register R0 with the RESET bit set, all other programmed values are ignored. After resetting
the device, the register R0 must be programmed again (with RESET = 0) to set non-default values in register R0.
The reset occurs on the falling edge of the LEuWire pin which loaded R0 with RESET = 1.
The RESET bit is automatically cleared upon writing any other register. For instance, when R0 is written to again
with default values.
Table 22. RESET
R0[17] STATE
0 Normal operation
1 Reset (automatically cleared)
8.6.3.1.6 POWERDOWN
The POWERDOWN bit is located in register R1 only. Setting the bit causes the device to enter powerdown
mode. Normal operation is resumed by clearing this bit with MICROWIRE.
Table 23. POWERDOWN
R1[17] STATE
0 Normal operation
1 Powerdown
8.6.3.1.7 CLKoutX_HS, Digital Delay Half Shift
This bit subtracts a half clock cycle of the clock distribution path period to the digital delay of CLKoutX.
CLKoutX_HS is used together with CLKoutX_DDLY to set the digital delay value.
When changing CLKoutX_HS, the digital delay immediately takes effect without a SYNC event.
Table 24. CLKoutX_HS
R0-R5[16] STATE
0 Normal
1Subtract half of a clock distribution path period from the total digital
delay
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(1) CLKoutX_HS must = 0 for divide by 1.
(2) After programming PLL2_N value, a SYNC must occur on channels using this divide value. Programming PLL2_N does generate a
SYNC event automatically which satisfies this requirement, but NO_SYNC_CLKoutX must be set to 0 for these clock outputs.
8.6.3.1.8 CLKoutX_DIV, Clock Output Divide
CLKoutX_DIV sets the divide value for the clock output. The divide may be even or odd. Both even and odd
divides output a 50% duty cycle clock.
Using a divide value of 26 or greater will cause the clock output to operate in extended mode regardless of the
clock output's digital delay value.
Programming CLKoutX_DIV can require special attention. See section Special Programming Case for R0 to R5
for CLKoutX_DIV and CLKoutX_DDLY for more details.
Table 25. CLKoutX_DIV, 11 Bits
R0-R5[15:5] DIVIDE VALUE POWER MODE
0 (0x00) Reserved
Normal Mode
1 (0x01) 1 (1)
2 (0x02) 2 (2)
3 (0x03) 3
4 (0x04) 4 (2)
5 (0x05) 5 (2)
6 (0x06) 6
... ...
24 (0x18) 24
25 (0x19) 25
26 (0x1A) 26
Extended Mode
27 (0x1B) 27
... ...
1044 (0x414) 1044
1045 (0x415) 1045
8.6.3.2 Registers R6 to R8
Registers R6 to R8 set the clock output types and analog delays.
8.6.3.2.1 CLKoutX_TYPE
The clock output types of the LMK04906 are individually programmable. The CLKoutX_TYPE registers set the
output type of an individual clock output to LVDS, LVPECL, LVCMOS, or powers down the output buffer. Note
that LVPECL supports four different amplitude levels and LVCMOS supports single LVCMOS outputs, inverted,
and normal polarity of each output pin for maximum flexibility. For lowest spurious levels, configure the LVCMOS
outputs as LVCMOS (Inv/Norm) or LVCMOS (Norm/Inv). LVCMOS (Inv/Inv) and LVCMOS (Norm/Norm) are the
worst for spurious levels.
The programming addresses table shows at what register and address the specified clock output
CLKoutX_TYPE register is located.
The CLKoutX_TYPE table shows the programming definition for these registers.
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Table 26. CLKoutX_TYPE Programming Addresses
CLKoutX PROGRAMMING ADDRESS
CLKout0 R6[23:20]
CLKout1 R6[27:24]
CLKout2 R723:20]
CLKout3 R7[27:24]
CLKout4 R8[19:16]
CLKout5 R8[27:24]
Table 27. CLKoutX_TYPE, 4 Bits
R6-R8[31:28, 27:24, 23:20] DEFINITION
0 (0x00) Power down
1 (0x01) LVDS
2 (0x02) LVPECL (700 mVpp)
3 (0x03) LVPECL (1200 mVpp)
4 (0x04) LVPECL (1600 mVpp)
5 (0x05) LVPECL (2000 mVpp)
6 (0x06) LVCMOS (Norm/Inv)
7 (0x07) LVCMOS (Inv/Norm)
8 (0x08) LVCMOS (Norm/Norm)
9 (0x09) LVCMOS (Inv/Inv)
10 (0x0A) LVCMOS (Low/Norm)
11 (0x0A) LVCMOS (Low/Inv)
12 (0x0C) LVCMOS (Norm/Low)
13 (0x0D) LVCMOS (Inv/Low)
14 (0x0E) LVCMOS (Low/Low)
8.6.3.2.2 CLKoutX_ADLY
These registers control the analog delay of the clock output CLKoutX. Adding analog delay to the output will
increase the noise floor of the output. For this analog delay to be active for a clock output, it must be selected
with CLKoutX_ADL_SEL. If neither clock output in a clock output selects the analog delay, then the analog delay
block is powered down.
In addition to the programmed delay, a fixed 500 ps of delay will be added by engaging the delay block.
The programming addresses table shows at what register and address the specified clock output
CLKoutX_ADLY register is located.
The CLKoutX_ADLY table shows the programming definition for these registers.
Table 28. CLKoutX_ADLY Programming Addresses
CLKoutX_ADLY PROGRAMMING ADDRESS
CLKout0_ADLY R6[9:5]
CLKout1_ADLY R6[15:11]
CLKout2_ADLY R7[9:5]
CLKout3_ADLY R7[15:11]
CLKout4_ADLY R8[9:5]
CLKout5_ADLY R8[15:11]
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Table 29. CLKoutX_ADLY, 5 Bits
R6-R8[15:11, 9:5] DEFINITION
0 (0x00) 500 ps + No delay
1 (0x01) 500 ps + 25 ps
2 (0x02) 500 ps + 50 ps
3 (0x03) 500 ps + 75 ps
4 (0x04) 500 ps + 100 ps
5 (0x05) 500 ps + 125 ps
6 (0x06) 500 ps + 150 ps
7 (0x07) 500 ps + 175 ps
8 (0x08) 500 ps + 200 ps
9 (0x09) 500 ps + 225 ps
10 (0x0A) 500 ps + 250 ps
11 (0x0B) 500 ps + 275 ps
12 (0x0C) 500 ps + 300 ps
13 (0x0D) 500 ps + 325 ps
14 (0x0E) 500 ps + 350 ps
15 (0x0F) 500 ps + 375 ps
16 (0x10) 500 ps + 400 ps
17 (0x11) 500 ps + 425 ps
18 (0x12) 500 ps + 450 ps
19 (0x13) 500 ps + 475 ps
20 (0x14) 500 ps + 500 ps
21 (0x15) 500 ps + 525 ps
22 (0x16) 500 ps + 550 ps
23 (0x17) 500 ps + 575 ps
8.6.3.3 Register R10
8.6.3.3.1 OSCout0_TYPE
The OSCout0 clock output has a programmable output type. The OSCout0_TYPE register sets the output type to
LVDS, LVPECL, LVCMOS, or powers down the output buffer. Note that LVPECL supports four different
amplitude levels and LVCMOS supports dual and single LVCMOS outputs with inverted, and normal polarity of
each output pin for maximum flexibility.
To turn on the output, the OSCout0_TYPE must be set to a non-power down setting and enabled with
EN_OSCout0, OSCout0 Output Enable.
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Table 30. OSCout0_TYPE, 4 Bits
R10[27:24] DEFINITION
0 (0x00) Powerdown
1 (0x01) LVDS
2 (0x02) LVPECL (700 mVpp)
3 (0x03) LVPECL (1200 mVpp)
4 (0x04) LVPECL (1600 mVpp)
5 (0x05) LVPECL (2000 mVpp)
6 (0x06) LVCMOS (Norm/Inv)
7 (0x07) LVCMOS (Inv/Norm)
8 (0x08) LVCMOS (Norm/Norm)
9 (0x09) LVCMOS (Inv/Inv)
10 (0x0A) LVCMOS (Low/Norm)
11 (0x0B) LVCMOS (Low/Inv)
12 (0x0C) LVCMOS (Norm/Low)
13 (0x0D) LVCMOS (Inv/Low)
14 (0x0E) LVCMOS (Low/Low)
8.6.3.3.2 EN_OSCout0, OSCout0 Output Enable
EN_OSCout0 is used to enable an oscillator buffered output.
Table 31. EN_OSCout0
R10[22] OUTPUT STATE
0 OSCout0 Disabled
1 OSCout0 Enabled
OSCout0 note: In addition to enabling the output with EN_OSCout0. The OSCout0_TYPE must be programmed
to a non-power down value for the output buffer to power up.
8.6.3.3.3 OSCout0_MUX, Clock Output Mux
Sets OSCout0 buffer to output a divided or bypassed OSCin signal. The divisor is set by OSCout_DIV, Oscillator
Output Divide.
Table 32. OSCout0_MUX
R10[20] MUX OUTPUT
0 Bypass divider
1 Divided
8.6.3.3.4 PD_OSCin, OSCin Powerdown Control
Except in clock distribution mode, the OSCin buffer must always be powered up.
In clock distribution mode, the OSCin buffer must be powered down if not used.
Table 33. PD_OSCin
R10[19] OSCin BUFFER
0 Normal Operation
1 Powerdown
8.6.3.3.5 OSCout_DIV, Oscillator Output Divide
The OSCout divider can be programmed from 2 to 8. Divide by 1 is achieved by bypassing the divider with
OSCout0_MUX, Clock Output Mux.
Note that OSCout_DIV will be in the PLL1 N feedback path if OSCout0_MUX selects divided as an output. When
OSCout_DIV is in the PLL1 N feedback path, the OSCout_DIV divide value must be accounted for when
programming PLL1 N.
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See PLL Programming for more information on programming PLL1 to lock.
Table 34. OSCout_DIV, 3 Bits
R10[18:16] DIVIDE
0 (0x00) 8
1 (0x01) 2
2 (0x02) 2
3 (0x03) 3
4 (0x04) 4
5 (0x05) 5
6 (0x06) 6
7 (0x07) 7
8.6.3.3.6 VCO_MUX
When the internal VCO is used, the VCO divider can be selected to divide the VCO output frequency to reduce
the frequency on the clock distribution path. It is recommended to use the VCO directly unless:
Very low output frequencies are required.
If using the VCO divider results in three or more clock output divider/delays changing from extended to
normal power mode, a small power savings may be achieved by using the VCO divider.
A consequence of using the VCO divider is a small degradation in phase noise.
Table 35. VCO_MUX
R10[12] DIVIDE
0 VCO selected
1 VCO divider selected
8.6.3.3.7 EN_FEEDBACK_MUX
When using 0-delay or dynamic digital delay (SYNC_QUAL = 1), EN_FEEDBACK_MUX must be set to 1 to
power up the feedback mux.
Table 36. EN_FEEDBACK_MUX
R10[11] DIVIDE
0 Feedback mux powered down
1 Feedback mux enabled
8.6.3.3.8 VCO_DIV, VCO Divider
Divide value of the VCO Divider.
See PLL Programming for more information on programming PLL2 to lock.
Table 37. VCO_DIV, 3 Bits
R10[10:8] DIVIDE
0 (0x00) 8
1 (0x01) 2
2 (0x02) 2
3 (0x03) 3
4 (0x04) 4
5 (0x05) 5
6 (0x06) 6
7 (0x07) 7
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8.6.3.3.9 FEEDBACK_MUX
When in 0-delay mode, the feedback mux selects the clock output to be fed back into the PLL1 N Divider.
Table 38. FEEDBACK_MUX, 3 Bits
R10[7:5] DIVIDE
0 (0x00) Reserved
1 (0x01) CLKout1
2 (0x02) Reserved
3 (0x03) CLKout3
4 (0x04) CLKout4
5 (0x05) CLKout5
6 (0x06) FBCLKin/FBCLKin*
8.6.3.4 REGISTER R11
8.6.3.4.1 MODE: Device Mode
MODE determines how the LMK04906 operates from a high level. Different blocks of the device can be powered
up and down for specific application requirements from a dual loop architecture to clock distribution.
The LMK04906 can operate in:
Dual PLL mode with the internal VCO or an external VCO.
Single PLL mode uses PLL2 and powers down PLL1. OSCin is used for PLL reference input.
Clock Distribution mode allows use of CLKin1 to distribute to clock outputs CLKout0 through CLKout11, and
OSCin to distribute to OSCout0, and optionally CLKout3 through CLKout9.
For the PLL modes, 0-delay can be used have deterministic phase with the input clock.
For the PLL modes it is also possible to use an external VCO.
Table 39. MODE, 5 Bits
R11[31:27] VALUE
0 (0x00) Dual PLL, Internal VCO
1 (0x01) Reserved
2 (0x02) Dual PLL, Internal VCO,
0-Delay
3 (0x03) Dual PLL, External VCO (Fin)
4 (0x04) Reserved
5 (0x05) Dual PLL, External VCO (Fin),
0-Delay
6 (0x06) PLL2, Internal VCO
7 (0x07) Reserved
8 (0x08) PLL2, Internal VCO,
0–Delay
9 (0x09) Reserved
10 (0x0A) Reserved
11 (0x0B) PLL2, External VCO (Fin)
12 (0x0C) Reserved
13 (0x0D) Reserved
14 (0x0E) Reserved
15 (0x0F) Reserved
16 (0x10) Clock Distribution
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8.6.3.4.2 EN_SYNC, Enable Synchronization
The EN_SYNC bit (default on) must be enabled for synchronization to work. Synchronization is required for
dynamic digital delay.
The synchronization enable may be turned off once the clocks are operating to save current. If EN_SYNC is set
after it has been cleared (a transition from 0 to 1), a SYNC is generated that can disrupt the active clock outputs.
Setting the NO_SYNC_CLKoutX bits will prevent this SYNC pulse from affecting the output clocks. Setting the
EN_SYNC bit is not a valid method for synchronizing the clock outputs. See the Clock Output Synchronization
(SYNC) for more information on synchronization.
Table 40. EN_SYNC
R11[26] DEFINITION
0 Synchronization disabled
1 Synchronization enabled
8.6.3.4.3 NO_SYNC_CLKoutX
The NO_SYNC_CLKoutX bits prevent individual clock outputs from becoming synchronized during a SYNC
event. A reason to prevent individual clock output from becoming synchronized is that during synchronization, the
clock output is in a fixed low state or can have a glitch pulse.
By disabling SYNC on a clock output, it will continue to operate normally during a SYNC event.
Digital delay requires a SYNC operation to take effect. If NO_SYNC_CLKoutX is set before a SYNC event, the
digital delay value will be unused.
Setting the NO_SYNC_CLKoutX bit has no effect on clocks already synchronized together.
Table 41. NO_SYNC_CLKoutX Programming Addresses
NO_SYNC_CLKoutX PROGRAMMING ADDRESS
CLKout0 R11:20
CLKout1 R11:21
CLKout2 R11:22
CLKout3 R11:23
CLKout4 R11:24
CLKout5 R11:25
Table 42. NO_SYNC_CLKoutX
R11[25, 24, 23, 22, 21, 20] DEFINITION
0 CLKoutX will synchronize
1 CLKoutX will not synchronize
8.6.3.4.4 SYNC_CLKin2_MUX
Mux controlling SYNC/Status_CLKin2 pin.
All the outputs logic is active high when SYNC_TYPE = 3 (Output). All the outputs logic is active low when
SYNC_TYPE = 4 (Output Inverted). For example, when SYNC_MUX = 0 (Logic Low) and SYNC_TYPE = 3
(Output) then SYNC outputs a logic low. When SYNC_MUX = 0 (Logic Low) and SYNC_TYPE = 4 (Output
Inverted) then SYNC outputs a logic high.
Table 43. SYNC_MUX, 2 Bits
R11[19:18] SYNC PIN OUTPUT
0 (0x00) Logic Low
1 (0x01) CLKin2 LOS
2 (0x02) CLKin2 Selected
3 (0x03) uWire Readback
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8.6.3.4.5 SYNC_QUAL
When SYNC_QUAL is set, clock outputs will be synchronized to an existing clock output selected by
FEEDBACK_MUX. By using the NO_SYNC_CLKoutX bits, selected clock outputs will not be interrupted during
the SYNC event.
Qualifying the SYNC by an output clock means that the pulse which turns the clock outputs off and on will have a
fixed time relationship to the qualifying output clock.
SYNC_QUAL = 1 requires CLKout2_PD = 0 for proper operation. CLKout2_TYPE may be set to Powerdown
mode.
See Clock Output Synchronization (SYNC) for more information.
Table 44. SYNC_QUAL
R11[17] MODE
0 No qualification
1Qualification by clock output from feedback mux
(Must set
CLKout2_PD = 0)
8.6.3.4.6 SYNC_POL_INV
Sets the polarity of the SYNC pin when input. When SYNC is asserted the clock outputs will transition to a low
state.
See Clock Output Synchronization (SYNC) for more information on SYNC. A SYNC event can be generated by
toggling this bit through the MICROWIRE interface.
Table 45. SYNC_POL_INV
R11[16] POLARITY
0 SYNC is active high
1 SYNC is active low
8.6.3.4.7 SYNC_EN_AUTO
When set, causes a SYNC event to occur when programming register R0 to R5 to adjust digital delay values.
The SYNC event will coincide with the LEuWire pin falling edge.
See Special Programming Case for R0 to R5 for CLKoutX_DIV and CLKoutX_DDLY for more information on
possible special programming considerations when SYNC_EN_AUTO = 1.
Table 46. SYNC_EN_AUTO
R11[15] MODE
0 Manual SYNC
1 SYNC Internally Generated
8.6.3.4.8 SYNC_TYPE
Sets the IO type of the SYNC pin.
Table 47. SYNC_TYPE, 3 Bits
R11[14:12] POLARITY
0 (0x00) Input
1 (0x01) Input /w pull-up resistor
2 (0x02) Input /w pull-down resistor
3 (0x03) Output (push-pull)
4 (0x04) Output inverted (push-pull)
5 (0x05) Output (open source)
6 (0x06) Output (open drain)
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When in output mode the SYNC input is forced to 0 regardless of the SYNC_MUX setting. A synchronization can
then be activated by uWire by programming the SYNC_POL_INV register to active low to assert SYNC. SYNC
can then be released by programming SYNC_POL_INV to active high. Using this uWire programming method to
create a SYNC event saves the need for an IO pin from another device.
8.6.3.4.9 EN_PLL2_XTAL
If an external crystal is being used to implement a discrete VCXO, the internal feedback amplifier must be
enabled with this bit in order to complete the oscillator circuit.
Table 48. EN_PLL2_XTAL
R11[5] OSCILLATOR AMPLIFIER STATE
0 Disabled
1 Enabled
(1) Only valid when HOLDOVER_MUX is not set to 2 (PLL2_DLD) or 3 (PLL1 & PLL2 DLD).
8.6.3.5 Register R12
8.6.3.5.1 LD_MUX
LD_MUX sets the output value of the LD pin.
All the outputs logic is active high when LD_TYPE = 3 (Output). All the outputs logic is active low when
LD_TYPE = 4 (Output Inverted). For example, when LD_MUX = 0 (Logic Low) and LD_TYPE = 3 (Output) then
Status_LD outputs a logic low. When LD_MUX = 0 (Logic Low) and LD_TYPE = 4 (Output Inverted) then
Status_LD outputs a logic high.
Table 49. LD_MUX, 5 Bits
R12[31:27] DIVIDE
0 (0x00) Logic Low
1 (0x01) PLL1 DLD
2 (0x02) PLL2 DLD
3 (0x03) PLL1 & PLL2 DLD
4 (0x04) Holdover Status
5 (0x05) DAC Locked
6 (0x06) Reserved
7 (0x07) uWire Readback
8 (0x08) DAC Rail
9 (0x09) DAC Low
10 (0x0A) DAC High
11 (0x0B) PLL1_N
12 (0x0C) PLL1_N/2
13 (0x0D) PLL2 N
14 (0x0E) PLL2 N/2
15 (0x0F) PLL1_R
16 (0x10) PLL1_R/2
17 (0x11) PLL2 R (1)
18 (0x12) PLL2 R/2 (1)
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8.6.3.5.2 LD_TYPE
Sets the IO type of the LD pin.
Table 50. LD_TYPE, 3 Bits
R12[26:24] POLARITY
0 (0x00) Reserved
1 (0x01) Reserved
2 (0x02) Reserved
3 (0x03) Output (push-pull)
4 (0x04) Output inverted (push-pull)
5 (0x05) Output (open source)
6 (0x06) Output (open drain)
8.6.3.5.3 SYNC_PLLX_DLD
By setting SYNC_PLLX_DLD a SYNC mode will be engaged (asserted SYNC) until PLL1 and/or PLL2 locks.
SYNC_QUAL must be 0 to use this functionality.
Table 51. SYNC_PLL2_DLD
R12[23] SYNC MODE FORCED
0 No
1 Yes
Table 52. SYNC_PLL1_DLD
R12[22] SYNC MODE FORCED
0 No
1 Yes
8.6.3.5.4 EN_TRACK
Enable the DAC to track the PLL1 tuning voltage. For optional use in in holdover mode.
Tracking can be used to monitor PLL1 voltage by readback of DAC_CNT register in any mode.
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Table 53. EN_TRACK
R12[8] DAC TRACKING
0 Disabled
1 Enabled
8.6.3.5.5 HOLDOVER_MODE
Enable the holdover mode.
Table 54. HOLDOVER_MODE, 2 Bits
R12[7:6] HOLDOVER MODE
0 Reserved
1 Disabled
2 Enabled
3 Reserved
(1) Only valid when LD_MUX is not set to 2 (PLL2_DLD) or 3 (PLL1 & PLL2 DLD).
8.6.3.6 Register R13
8.6.3.6.1 HOLDOVER_MUX
HOLDOVER_MUX sets the output value of the Status_Holdover pin.
The outputs are active high when HOLDOVER_TYPE = 3 (Output). The outputs are active low when
HOLDOVER_TYPE = 4 (Output Inverted).
Table 55. HOLDOVER_MUX, 5 Bits
R13[31:27] DIVIDE
0 (0x00) Logic Low
1 (0x01) PLL1 DLD
2 (0x02) PLL2 DLD
3 (0x03) PLL1 & PLL2 DLD
4 (0x04) Holdover Status
5 (0x05) DAC Locked
6 (0x06) Reserved
7 (0x07) uWire Readback
8 (0x08) DAC Rail
9 (0x09) DAC Low
10 (0x0A) DAC High
11 (0x0B) PLL1 N
12 (0x0C) PLL1 N/2
13 (0x0D) PLL2 N
14 (0x0E) PLL2 N/2
15 (0x0F) PLL1 R
16 (0x10) PLL1 R/2
17 (0x11) PLL2 R (1)
18 (0x12) PLL2 R/2 (1)
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8.6.3.6.2 HOLDOVER_TYPE
Sets the IO mode of the Status_Holdover pin.
Table 56. HOLDOVER_TYPE, 3 Bits
R13[26:24] POLARITY
0 (0x00) Reserved
1 (0x01) Reserved
2 (0x02) Reserved
3 (0x03) Output (push-pull)
4 (0x04) Output inverted (push-pull)
5 (0x05) Output (open source)
6 (0x06) Output (open drain)
8.6.3.6.3 Status_CLKin1_MUX
Status_CLKin1_MUX sets the output value of the Status_CLKin1 pin. If Status_CLKin1_TYPE is set to an input
type, this register has no effect. This MUX register only sets the output signal.
The outputs are active high when Status_CLKin1_TYPE = 3 (Output). The outputs are active low when
Status_CLKin1_TYPE = 4 (Output Inverted).
Table 57. Status_CLKin1_MUX, 3 Bits
R13[22:20] DIVIDE
0 (0x00) Logic Low
1 (0x01) CLKin1 LOS
2 (0x02) CLKin1 Selected
3 (0x03) DAC Locked
4 (0x04) DAC Low
5 (0x05) DAC High
6 (0x06) uWire Readback
8.6.3.6.4 Status_CLKin0_TYPE
Status_CLKin0_TYPE sets the IO type of the Status_CLKin0 pin.
Table 58. Status_CLKin0_TYPE, 3 Bits
R13[18:16] POLARITY
0 (0x00) Input
1 (0x01) Input /w pull-up resistor
2 (0x02) Input /w pull-down resistor
3 (0x03) Output (push-pull)
4 (0x04) Output inverted (push-pull)
5 (0x05) Output (open source)
6 (0x06) Output (open drain)
8.6.3.6.5 DISABLE_DLD1_DET
DISABLE_DLD1_DET disables the HOLDOVER mode from being activated when PLL1 lock detect signal
transitions from high to low.
When using Pin Select Mode as the input clock switch mode, this bit should normally be set.
Table 59. DISABLE_DLD1_DET
R13[15] HOLDOVER DLD1 DETECT
0 PLL1 DLD causes clock switch event
1 PLL1 DLD does not cause clock switch event
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8.6.3.6.6 Status_CLKin0_MUX
CLKin0_MUX sets the output value of the Status_CLKin0 pin. If Status_CLKin0_TYPE is set to an input type, this
register has no effect. This MUX register only sets the output signal.
The outputs logic is active high when Status_CLKin0_TYPE = 3 (Output). The outputs logic is active low when
Status_CLKin0_TYPE = 4 (Output Inverted).
Table 60. Status_CLKin0_MUX, 3 Bits
R13[14:12] DIVIDE
0 (0x00) Logic Low
1 (0x01) CLKin0 LOS
2 (0x02) CLKin0 Selected
3 (0x03) DAC Locked
4 (0x04) DAC Low
5 (0x05) DAC High
6 (0x06) uWire Readback
8.6.3.6.7 CLKin_SELECT_MODE
CLKin_SELECT_MODE sets the mode used in determining reference CLKin for PLL1.
Table 61. CLKin_SELECT_MODE, 3 Bits
R13[11:9] MODE
0 (0x00) CLKin0 Manual
1 (0x01) CLKin1 Manual
2 (0x02) CLKin2 Manual
3 (0x03) Pin Select Mode
4 (0x04) Auto Mode
5 (0x05) Reserved
6 (0x06) Auto mode & next clock pin select
7 (0x07) Reserved
8.6.3.6.8 CLKin_Sel_INV
CLKin_Sel_INV sets the input polarity of Status_CLKin0 and Status_CLKin1 pins (Auto modes only).
Table 62. CLKin_Sel_INV
R13[8] INPUT
0 Active High
1 Active Low
8.6.3.6.9 EN_CLKinX
Each clock input can individually be enabled to be used during auto-switching CLKin_SELECT_MODE. Clock
input switching priority is always CLKin0 CLKin1 CLKin2 CLKin0.
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Table 63. EN_CLKin2
R13[7] INPUT
0 No
1 Yes
Table 64. EN_CLKin1
R13[6] VALID
0 No
1 Yes
Table 65. EN_CLKin0
R13[5] VALID
0 No
1 Yes
8.6.3.7 Register 14
8.6.3.7.1 LOS_TIMEOUT
This bit controls the amount of time in which no activity on a CLKin causes LOS (Loss-of-Signal) to be asserted.
Table 66. LOS_TIMEOUT, 2 Bits
R14[31:30] TIMEOUT
0 (0x00) 1200 ns, 420 kHz
1 (0x01) 206 ns, 2.5 MHz
2 (0x02) 52.9 ns, 10 MHz
3 (0x03) 23.7 ns, 22 MHz
8.6.3.7.2 EN_LOS
Enables the LOS (Loss-of-Signal) timeout control.
Table 67. EN_LOS
R14[28] LOS
0 Disabled
1 Enabled
8.6.3.7.3 Status_CLKin1_TYPE
Sets the IO type of the Status_CLKin1 pin.
Table 68. Status_CLKin1_TYPE, 3 Bits
R14[26:24] POLARITY
0 (0x00) Input
1 (0x01) Input /w pull-up resistor
2 (0x02) Input /w pull-down resistor
3 (0x03) Output (push-pull)
4 (0x04) Output inverted (push-pull)
5 (0x05) Output (open source)
6 (0x06) Output (open drain)
8.6.3.7.4 CLKinX_BUF_TYPE, PLL1 CLKinX/CLKinX* Buffer Type
There are two input buffer types for the PLL1 reference clock inputs: either bipolar or CMOS. Bipolar is
recommended for differential inputs such as LVDS and LVPECL. CMOS is recommended for DC coupled single
ended inputs.
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When using bipolar, CLKinX and CLKinX* input pins must be AC coupled when using a differential or single
ended input.
When using CMOS, CLKinX and CLKinX* input pins may be AC or DC coupled with a differential input.
When using CMOS in single ended mode, the unused clock input pin (CLKinX or CLKinX*) must be AC
grounded. The used clock input pin (CLKinX* or CLKinX) may be AC or DC coupled to the signal source.
The programming addresses table shows at what register and address the specified CLKinX_BUF_TYPE bit is
located.
The CLKinX_BUF_TYPE table shows the programming definition for these registers.
Table 69. CLKinX_BUF_TYPE Programming Addresses
CLKinX_BUF_TYPE PROGRAMMING ADDRESS
CLKin2_BUF_TYPE R14[22]
CLKin1_BUF_TYPE R14[21]
CLKin0_BUF_TYPE R14[20]
Table 70. CLKinX_BUF_TYPE
R14[22, 21, 20] CLKinX BUFFER TYPE
0 Bipolar
1 CMOS
8.6.3.7.5 DAC_HIGH_TRIP
Voltage from Vcc at which holdover mode is entered if EN_VTUNE_RAIL_DAC is enabled. Will also set flags
which can be monitored out Status_LD/Status_Holdover pins.
Step size is ~51 mV
Table 71. DAC_HIGH_TRIP, 6 Bits
R14[19:14] TRIP VOLTAGE FROM VCC (V)
0 (0x00) 1 × Vcc / 64
1 (0x01) 2 × Vcc / 64
2 (0x02) 3 × Vcc / 64
3 (0x03) 4 × Vcc / 64
4 (0x04) 5 × Vcc / 64
... ...
61 (0x3D) 62 × Vcc / 64
62 (0x3E) 63 × Vcc / 64
63 (0x3F) 64 × Vcc / 64
8.6.3.7.6 DAC_LOW_TRIP
Voltage from GND at which holdover mode is entered if EN_VTUNE_RAIL_DAC is enabled. Will also set flags
which can be monitored out Status_LD/Status_Holdover pins.
Step size is ~51 mV
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Table 72. DAC_LOW_TRIP, 6 Bits
R14[11:6] TRIP VOLTAGE FROM GND (V)
0 (0x00) 1 × Vcc / 64
1 (0x01) 2 × Vcc / 64
2 (0x02) 3 × Vcc / 64
3 (0x03) 4 × Vcc / 64
4 (0x04) 5 × Vcc / 64
... ...
61 (0x3D) 62 × Vcc / 64
62 (0x3E) 63 × Vcc / 64
63 (0x3F) 64 × Vcc / 64
8.6.3.7.7 EN_VTUNE_RAIL_DET
Enables the DAC Vtune rail detection. When the DAC achieves a specified Vtune, if this bit is enabled, the
current clock input is considered invalid and an input clock switch event is generated.
Table 73. EN_VTUNE_RAIL_DET
R14[5] STATE
0 Disabled
1 Enabled
8.6.3.8 Register 15
8.6.3.8.1 MAN_DAC
Sets the DAC value when in manual DAC mode in approximately 3.2-mV steps.
Table 74. MAN_DAC, 10 Bits
R15[31:22] DAC VOLTAGE
0 (0x00) 0 × Vcc / 1023
1 (0x01) 1 × Vcc / 1023
2 (0x02) 2 × Vcc / 1023
... ...
1023 (0x3FF) 1023 × Vcc / 1023
8.6.3.8.2 EN_MAN_DAC
This bit enables the manual DAC mode.
Table 75. EN_MAN_DAC
R15[20] DAC MODE
0 Automatic
1 Manual
8.6.3.8.3 HOLDOVER_DLD_CNT
Lock must be valid for this many clocks of PLL1 PDF before holdover mode is exited.
Table 76. HOLDOVER_DLD_CNT, 14 Bits
R15[19:6] EXIT COUNTS
0 (0x00) Reserved
1 (0x01) 1
2 (0x02) 2
... ...
16,383 (0x3FFF) 16,383
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8.6.3.8.4 FORCE_HOLDOVER
This bit forces the holdover mode.
When holdover is forced, if in fixed CPout1 mode, then the DAC will set the programmed MAN_DAC value. If in
tracked CPout1 mode, then the DAC will set the current tracked DAC value.
Setting FORCE_HOLDOVER does not constitute a clock input switch event unless DISABLE_DLD1_DET = 0,
since in holdover mode, PLL1_DLD = 0 this will trigger the clock input switch event.
Table 77. FORCE_HOLDOVER
R15[5] HOLDOVER
0 Disabled
1 Enabled
(1) At crystal frequency of 20.48 MHz
8.6.3.9 Register 16
8.6.3.9.1 XTAL_LVL
Sets the peak amplitude on the tunable crystal.
Increasing this value can improve the crystal oscillator phase noise performance at the cost of increased current
and higher crystal power dissipation levels.
Table 78. XTAL_LVL, 2 Bits
R15[31:22] PEAK AMPLITUDE(1)
0 (0x00) 1.65 Vpp
1 (0x01) 1.75 Vpp
2 (0x02) 1.90 Vpp
3 (0x03) 2.05 Vpp
8.6.3.10 Register 23
This register must not be programmed, it is a readback only register.
8.6.3.10.1 DAC_CNT
The DAC_CNT register is 10 bits in size and located at readback bit position [23:14]. When using tracking mode
for holdover, the DAC value can be readback at this address.
8.6.3.11 Register 24
8.6.3.11.1 PLL2_C4_LF, PLL2 Integrated Loop Filter Component
Internal loop filter components are available for PLL2, enabling either 3rd or 4th order loop filters without
requiring external components.
Internal loop filter capacitor C4 can be set according to the following table.
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Table 79. PLL2_C4_LF, 4 Bits
R24[31:28] LOOP FILTER CAPACITANCE (pF)
0 (0x00) 10 pF
1 (0x01) 15 pF
2 (0x02) 29 pF
3 (0x03) 34 pF
4 (0x04) 47 pF
5 (0x05) 52 pF
6 (0x06) 66 pF
7 (0x07) 71 pF
8 (0x08) 103 pF
9 (0x09) 108 pF
10 (0x0A) 122 pF
11 (0x0B) 126 pF
12 (0x0C) 141 pF
13 (0x0D) 146 pF
14 (0x0E) Reserved
15 (0x0F) Reserved
8.6.3.11.2 PLL2_C3_LF, PLL2 Integrated Loop Filter Component
Internal loop filter components are available for PLL2, enabling either 3rd or 4th order loop filters without
requiring external components.
Internal loop filter capacitor C3 can be set according to the following table.
Table 80. PLL2_C3_LF, 4 Bits
R24[27:24] LOOP FILTER CAPACITANCE (pF)
0 (0x00) 10 pF
1 (0x01) 11 pF
2 (0x02) 15 pF
3 (0x03) 16 pF
4 (0x04) 19 pF
5 (0x05) 20 pF
6 (0x06) 24 pF
7 (0x07) 25 pF
8 (0x08) 29 pF
9 (0x09) 30 pF
10 (0x0A) 33 pF
11 (0x0B) 34 pF
12 (0x0C) 38 pF
13 (0x0D) 39 pF
14 (0x0E) Reserved
15 (0x0F) Reserved
8.6.3.11.3 PLL2_R4_LF, PLL2 Integrated Loop Filter Component
Internal loop filter components are available for PLL2, enabling either 3rd or 4th order loop filters without
requiring external components.
Internal loop filter resistor R4 can be set according to the following table.
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Table 81. PLL2_R4_LF, 3 Bits
R24[22:20] RESISTANCE
0 (0x00) 200 Ω
1 (0x01) 1 kΩ
2 (0x02) 2 kΩ
3 (0x03) 4 kΩ
4 (0x04) 16 kΩ
5 (0x05) Reserved
6 (0x06) Reserved
7 (0x07) Reserved
8.6.3.11.4 PLL2_R3_LF, PLL2 Integrated Loop Filter Component
Internal loop filter components are available for PLL2, enabling either 3rd or 4th order loop filters without
requiring external components.
Internal loop filter resistor R3 can be set according to Table 82.
Table 82. PLL2_R3_LF, 3 Bits
R24[18:16] RESISTANCE
0 (0x00) 200 Ω
1 (0x01) 1 kΩ
2 (0x02) 2 kΩ
3 (0x03) 4 kΩ
4 (0x04) 16 kΩ
5 (0x05) Reserved
6 (0x06) Reserved
7 (0x07) Reserved
8.6.3.11.5 PLL1_N_DLY
Increasing delay of PLL1_N_DLY will cause the outputs to lead from CLKinX. For use in 0-delay mode.
Table 83. PLL1_N_DLY, 3 Bits
R24[14:12] DEFINITION
0 (0x00) 0 ps
1 (0x01) 205 ps
2 (0x02) 410 ps
3 (0x03) 615 ps
4 (0x04) 820 ps
5 (0x05) 1025 ps
6 (0x06) 1230 ps
7 (0x07) 1435 ps
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8.6.3.11.6 PLL1_R_DLY
Increasing delay of PLL1_R_DLY will cause the outputs to lag from CLKinX. For use in 0-delay mode.
Table 84. PLL1_R_DLY, 3 Bits
R24[10:8] DEFINITION
0 (0x00) 0 ps
1 (0x01) 205 ps
2 (0x02) 410 ps
3 (0x03) 615 ps
4 (0x04) 820 ps
5 (0x05) 1025 ps
6 (0x06) 1230 ps
7 (0x07) 1435 ps
8.6.3.11.7 PLL1_WND_SIZE
PLL1_WND_SIZE sets the window size used for digital lock detect for PLL1. If the phase error between the
reference and feedback of PLL1 is less than specified time, then the PLL1 lock counter increments.
See Digital Lock Detect Frequency Accuracy for more information.
Table 85. PLL1_WND_SIZE, 2 Bits
R24[7:6] DEFINITION
0 5.5 ns
1 10 ns
2 18.6 ns
3 40 ns
8.6.3.12 Register 25
8.6.3.12.1 DAC_CLK_DIV
The DAC update clock frequency is the PLL1 phase detector frequency divided by this divisor.
Table 86. DAC_CLK_DIV, 10 Bits
R25[31:22] DIVIDE
0 (0x00) Reserved
1 (0x01) 1
2 (0x02) 2
3 (0x03) 3
... ...
1,022 (0x3FE) 1022
1,023 (0x3FF) 1023
8.6.3.12.2 PLL1_DLD_CNT
The reference and feedback of PLL1 must be within the window of phase error as specified by PLL1_WND_SIZE
for this many phase detector cycles before PLL1 digital lock detect is asserted.
See Digital Lock Detect Frequency Accuracy for more information.
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Table 87. PLL1_DLD_CNT, 14 Bits
R25[19:6] DIVIDE
0 Reserved
1 1
2 2
3 3
... ...
16,382 (0x3FFE) 16,382
16,383 (0x3FFF) 16,383
8.6.3.13 Register 26
8.6.3.13.1 PLL2_WND_SIZE
PLL2_WND_SIZE sets the window size used for digital lock detect for PLL2. If the phase error between the
reference and feedback of PLL2 is less than specified time, then the PLL2 lock counter increments. This value
must be programmed to 2 (3.7 ns).
See Digital Lock Detect Frequency Accuracy for more information.
Table 88. PLL2_WND_SIZE, 2 Bits
R26[31:30] DEFINITION
0 Reserved
1 Reserved
2 3.7 ns
3 Reserved
(1) When the doubler is not enabled, PLL2_R should not be programmed to 1.
8.6.3.13.2 EN_PLL2_REF_2X, PLL2 Reference Frequency Doubler
Enabling the PLL2 reference frequency doubler allows for higher phase detector frequencies on PLL2 than would
normally be allowed with the given VCXO or Crystal frequency.
Higher phase detector frequencies reduces the PLL N values which makes the design of wider loop bandwidth
filters possible.
See PLL Programming for more information on how to program the PLL dividers to lock the PLL.
Table 89. EN_PLL2_REF_2X
R26[29] DESCRIPTION
0Reference frequency normal
(1)
1 Reference frequency doubled (2x)
8.6.3.13.3 PLL2_CP_POL, PLL2 Charge Pump Polarity
PLL2_CP_POL sets the charge pump polarity for PLL2. The internal VCO requires the negative charge pump
polarity to be selected. Many VCOs use positive slope.
A positive slope VCO increases output frequency with increasing voltage. A negative slope VCO decreases
output frequency with increasing voltage.
Table 90. PLL2_CP_POL
R26[28] DESCRIPTION
0 Negative Slope VCO/VCXO
1 Positive Slope VCO/VCXO
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8.6.3.13.4 PLL2_CP_GAIN, PLL2 Charge Pump Current
This bit programs the PLL2 charge pump output current level. The table below also illustrates the impact of the
PLL2 TRI-STATE bit in conjunction with PLL2_CP_GAIN.
Table 91. PLL2_CP_GAIN, 2 Bits
R26[27:26] PLL2_CP_TRI
R27[5] CHARGE PUMP CURRENT (µA)
X 1 Hi-Z
0 (0x00) 0 100
1 (0x01) 0 400
2 (0x02) 0 1600
3 (0x03) 0 3200
8.6.3.13.5 PLL2_DLD_CNT
The reference and feedback of PLL2 must be within the window of phase error as specified by PLL2_WND_SIZE
for PLL2_DLD_CNT cycles before PLL2 digital lock detect is asserted.
See Digital Lock Detect Frequency Accuracy for more information
Table 92. PLL2_DLD_CNT, 14 Bits
R26[19:6] DIVIDE
0 (0x00) Reserved
1 (0x01) 1
2 (0x02) 2
3 (0x03) 3
... ...
16,382 (0x3FFE) 16,382
16,383 (0x3FFF) 16,383
8.6.3.13.6 PLL2_CP_TRI, PLL2 Charge Pump TRI-STATE
This bit allows for the PLL2 charge pump output pin, CPout2, to be placed into TRI-STATE.
Table 93. PLL2_CP_TRI
R26[5] DESCRIPTION
0 PLL2 CPout2 is active
1 PLL2 CPout2 is at TRI-STATE
8.6.3.14 Register 27
8.6.3.14.1 PLL1_CP_POL, PLL1 Charge Pump Polarity
PLL1_CP_POL sets the charge pump polarity for PLL1. Many VCXOs use positive slope.
A positive slope VCXO increases output frequency with increasing voltage. A negative slope VCXO decreases
output frequency with increasing voltage.
Table 94. PLL1_CP_POL
R27[28] DESCRIPTION
0 Negative Slope VCO/VCXO
1 Positive Slope VCO/VCXO
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8.6.3.14.2 PLL1_CP_GAIN, PLL1 Charge Pump Current
This bit programs the PLL1 charge pump output current level. The table below also illustrates the impact of the
PLL1 TRI-STATE bit in conjunction with PLL1_CP_GAIN.
Table 95. PLL1_CP_GAIN, 2 Bits
R26[27:26] PLL1_CP_TRI
R27[5] CHARGE PUMP CURRENT (µA)
X 1 Hi-Z
0 (0x00) 0 100
1 (0x01) 0 200
2 (0x02) 0 400
3 (0x03) 0 1600
8.6.3.14.3 CLKinX_PreR_DIV
The pre-R dividers before the PLL1 R divider can be programmed such that when the active clock input is
switched, the frequency at the input of the PLL1 R divider will be the same. This allows PLL1 to stay in lock
without needing to re-program the PLL1 R register when different clock input frequencies are used. This is
especially useful in the auto CLKin switching modes.
Table 96. CLKinX_PreR_DIV Programming Addresses
CLKinX_PreR_DIV PROGRAMMING ADDRESS
CLKin2_PreR_DIV R27[25:24]
CLKin1_PreR_DIV R27[23:22]
CLKin0_PreR_DIV R27[21:20]
Table 97. CLKinX_PreR_DIV, 2 Bits
R27[25:24, 23:22, 21:20] DIVIDE
0 (0x00) 1
1 (0x01) 2
2 (0x02) 4
3 (0x03) 8
8.6.3.14.4 PLL1_R, PLL1 R Divider
The reference path into the PLL1 phase detector includes the PLL1 R divider. See PLL Programming for more
information on how to program the PLL dividers to lock the PLL.
The valid values for PLL1_R are shown in the table below.
Table 98. PLL1_R, 14 Bits
R27[19:6] DIVIDE
0 (0x00) Reserved
1 (0x01) 1
2 (0x02) 2
3 (0x03) 3
... ...
16,382 (0x3FFE) 16,382
16,383 (0x3FFF) 16,383
8.6.3.14.5 PLL1_CP_TRI, PLL1 Charge Pump TRI-STATE
This bit allows for the PLL1 charge pump output pin, CPout1, to be placed into TRI-STATE.
Table 99. PLL1_CP_TRI
R27[5] DESCRIPTION
0 PLL1 CPout1 is active
1 PLL1 CPout1 is at TRI-STATE
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(1) When using PLL2_R divide value of 1, the PLL2 reference doubler should be used (EN_PLL2_REF_2X = 1).
8.6.3.15 Register 28
8.6.3.15.1 PLL2_R, PLL2 R Divider
The reference path into the PLL2 phase detector includes the PLL2 R divider.
See PLL Programming for more information on how to program the PLL dividers to lock the PLL.
Table 100 shows the valid values for PLL2_R .
Table 100. PLL2_R, 12 Bits
R28[31:20] DIVIDE
0 (0x00) Not Valid
1 (0x01) 1 (1)
2 (0x02) 2
3 (0x03) 3
... ...
4,094 (0xFFE) 4,094
4,095 (0xFFF) 4,095
8.6.3.15.2 PLL1_N, PLL1 N Divider
The feedback path into the PLL1 phase detector includes the PLL1 N divider.
See PLL Programming for more information on how to program the PLL dividers to lock the PLL.
Table 101 shows the valid values for PLL1_N.
Table 101. PLL1_N, 14 Bits
R28[19:6] DIVIDE
0 (0x00) Not Valid
1 (0x01) 1
2 (0x02) 2
... ...
4,095 (0xFFF) 4,095
8.6.3.16 REGISTER 29
8.6.3.16.1 OSCin_FREQ, PLL2 Oscillator Input Frequency Register
The frequency of the PLL2 reference input to the PLL2 Phase Detector (OSCin/OSCin* port) must be
programmed to support proper operation of the frequency calibration routine which locks the internal VCO to the
target frequency.
Table 102. OSCin_FREQ, 3 Bits
R29[26:24] OSCin FREQUENCY
0 (0x00) 0 to 63 MHz
1 (0x01) >63 MHz to 127 MHz
2 (0x02) >127 MHz to 255 MHz
3 (0x03) Reserved
4 (0x04) >255 MHz to 400 MHz
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8.6.3.16.2 PLL2_FAST_PDF, High PLL2 Phase Detector Frequency
When PLL2 phase detector frequency is greater than 100 MHz, set the PLL2_FAST_PDF to ensure proper
operation of device.
Table 103. PLL2_FAST_PDF
R29[23] PLL2 PDF
0Less than or
equal to 100 MHz
1 Greater than 100 MHz
8.6.3.16.3 PLL2_N_CAL, PLL2 N Calibration Divider
During the frequency calibration routine, the PLL uses the divide value of the PLL2_N_CAL register instead of
the divide value of the PLL2_N register to lock the VCO to the target frequency.
See PLL Programming for more information on how to program the PLL dividers to lock the PLL.
Table 104. PLL2_N_CAL, 18 Bits
R30[22:5] DIVIDE
0 (0x00) Not Valid
1 (0x01) 1
2 (0x02) 2
... ...
262,143 (0x3FFFF) 262,143
8.6.3.17 Register 30
If an internal VCO mode is used, programming Register 30 triggers the frequency calibration routine. This
calibration routine will also generate a SYNC event. See Clock Output Synchronization (SYNC) for more details
on a SYNC.
8.6.3.17.1 PLL2_P, PLL2 N Prescaler Divider
The PLL2 N Prescaler divides the output of the VCO as selected by Mode_MUX1 and is connected to the PLL2
N divider.
See PLL Programming for more information on how to program the PLL dividers to lock the PLL.
Table 105. PLL2_P, 3 Bits
R30[26:24] DIVIDE VALUE
0 (0x00) 8
1 (0x01) 2
2 (0x02) 2
3 (0x03) 3
4 (0x04) 4
5 (0x05) 5
6 (0x06) 6
7 (0x07) 7
8.6.3.17.2 PLL2_N, PLL2 N Divider
The feeback path into the PLL2 phase detector includes the PLL2 N divider.
Each time register 30 is updated via the MICROWIRE interface, a frequency calibration routine runs to lock the
VCO to the target frequency. During this calibration PLL2_N is substituted with PLL2_N_CAL.
See PLL Programming for more information on how to program the PLL dividers to lock the PLL.
Table 106 shows the valid values for PLL2_N.
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Table 106. PLL2_N, 18 Bits
R30[22:5] DIVIDE
0 (0x00) Not Valid
1 (0x01) 1
2 (0x02) 2
... ...
262,143 (0x3FFFF) 262,143
8.6.3.18 Register 31
8.6.3.18.1 READBACK_LE
Sets the required state of the LEuWire pin when performing register readback.
See Readback.
Table 107. READBACK_LE
R31[21] REGISTER
0 (0x00) LE must be low for readback
1 (0x01) LE must be high for readback
8.6.3.18.2 READBACK_ADDR
Sets the address of the register to read back when performing readback.
When reading register 12, the READBACK_ADDR will be read back at R12[20:16].
When reading back from R31 bits 6 to 31 should be ignored. Only uWire_LOCK is valid.
See Register Readback for more information on readback.
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Table 108. READBACK_ADDR, 5 Bits
R31[20:16] REGISTER
0 (0x00) R0
1 (0x01) R1
2 (0x02) R2
3 (0x03) R3
4 (0x04) R4
5 (0x05) R5
6 (0x06) R6
7 (0x07) R7
8 (0x08) R8
9 (0x09) Reserved
10 (0x0A) R10
11 (0x0B) R11
12 (0x0C) R12
13 (0x0D) R13
14 (0x0E) R14
15 (0x0F) R15
16 (0x10) Reserved
17 (0x11) Reserved
... ...
22 (0x16) Reserved
23 (0x17) Reserved
24 (0x18) R24
25 (0x19) R25
26 (0x1A) R26
27 (0x1B) R27
28 (0x1C) R28
29 (0x1D) R29
30 (0x1E) R30
31 (0x1F) R31
8.6.3.18.3 uWire_LOCK
Setting uWire_LOCK will prevent any changes to uWire registers R0 to R30. Only by clearing the uWire_LOCK
bit in R31 can the uWire registers be unlocked and written to once more.
It is not necessary to lock the registers to perform a readback operation.
Table 109. uWire_LOCK
R31[5] STATE
0 Registers unlocked
1 Registers locked, Write-protect
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9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
To assist customers in frequency planning and design of loop filters, Texas Instruments provides the Clock
Design Tool and Clock Architect.
9.1.1 Loop Filter
Each PLL of the LMK04906 requires a dedicated loop filter.
9.1.1.1 PLL1
The loop filter for PLL1 must be connected to the CPout1 pin. Figure 20 shows a simple 2-pole loop filter. The
output of the filter drives an external VCXO module or discrete implementation of a VCXO using a crystal
resonator and external varactor diode. Higher order loop filters may be implemented using additional external R
and C components. It is recommended the loop filter for PLL1 result in a total closed loop bandwidth in the range
of 10 Hz to 200 Hz. The design of the loop filter is application specific and highly dependent on parameters such
as the phase noise of the reference clock, VCXO phase noise, and phase detector frequency for PLL1. TI's
Clock Conditioner Owner’s Manual covers this topic in detail and TI's Clock Design Tool can be used to simulate
loop filter designs for both PLLs.
These resources may be found: Clock and Timing landing page.
9.1.1.2 PLL2
As shown in Figure 20, the charge pump for PLL2 is directly connected to the optional internal loop filter
components, which are normally used only if either a third or fourth pole is needed. The first and second poles
are implemented with external components. The loop must be designed to be stable over the entire application-
specific tuning range of the VCO. The designer should note the range of KVCO listed in Electrical Characteristics
and how this value can change over the expected range of VCO tuning frequencies. Because loop bandwidth is
directly proportional to KVCO, the designer should model and simulate the loop at the expected extremes of the
desired tuning range, using the appropriate values for KVCO.
When designing with the integrated loop filter of the LMK04906 family, considerations for minimum resistor
thermal noise often lead one to the decision to design for the minimum value for integrated resistors, R3 and R4.
Both the integrated loop filter resistors (R3 and R4) and capacitors (C3 and C4) also restrict the maximum loop
bandwidth. However, these integrated components do have the advantage that they are closer to the VCO and
can therefore filter out some noise and spurs better than external components. For this reason, a common
strategy is to minimize the internal loop filter resistors and then design for the largest internal capacitor values
that permit a wide enough loop bandwidth. In situations where spur requirements are very stringent and there is
margin on phase noise, a feasible strategy would be to design a loop filter with integrated resistor values larger
than their minimum value.
0.1 PF
0.1 PFLMK04906
Input
100:
100:Trace
(Differential)
CLKinX
CLKinX*
LVPECL
Ref Clk
240:240:
0.1 PF
0.1 PF
0.1 PF
0.1 PFLMK04906
Input
100:
100:Trace
(Differential)
CLKinX
CLKinX*
LVDS
PLL2
Phase
Detector
C4
R3 R4
LMK04906 PLL2
PLL2 Internal Loop Filter
PLL2 External Loop
Filter
LMK04906 PLL1
PLL1 External Loop
Filter
CPout2
External VCXO
Internal VCO
C3
PLL1
Phase
Detector
LF1_C2
LF1_R2
LF1_C1
CPout1
LF2_C2
LF2_R2
LF2_C1
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Application Information (continued)
Figure 20. PLL1 and PLL2 Loop Filters
9.1.2 Driving CLKin and OSCin Inputs
9.1.2.1 Driving CLKin Pins With a Differential Source
Both CLKin ports can be driven by differential signals. It is recommended that the input mode be set to bipolar
(CLKinX_BUF_TYPE = 0) when using differential reference clocks. The LMK04906 family internally biases the
input pins so the differential interface should be AC coupled. The recommended circuits for driving the CLKin
pins with either LVDS or LVPECL are shown in Figure 21 and Figure 22.
Figure 21. CLKinX/X* Termination for an LVDS Reference Clock Source
Figure 22. CLKinX/X* Termination for an LVPECL Reference Clock Source
0.1 PF
0.1 PF
50:Trace
50:LMK04906
Clock Source
CLKinX
CLKinX*
0.1 PF
0.1 PFLMK04906
Input
100:
100:Trace
(Differential)
Differential
Sinewave Clock
Source
CLKinX
CLKinX*
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Application Information (continued)
Finally, a reference clock source that produces a differential sine wave output can drive the CLKin pins using the
following circuit. Note: the signal level must conform to the requirements for the CLKin pins listed in Electrical
Characteristics.
Figure 23. CLKinX/X* Termination for a Differential Sinewave Reference Clock Source
9.1.2.2 Driving CLKin Pins With a Single-Ended Source
The CLKin pins of the LMK04906 family can be driven using a single-ended reference clock source, for example,
either a sine wave source or an LVCMOS/LVTTL source. Either AC coupling or DC coupling may be used. In the
case of the sine wave source that is expecting a 50-Ωload, it is recommended that AC coupling be used as
shown in the circuit below with a 50-Ωtermination.
NOTE
The signal level must conform to the requirements for the CLKin pins listed in the
Electrical Characteristics table. CLKinX_BUF_TYPE in Register 11 is recommended to be
set to bipolar mode (CLKinX_BUF_TYPE = 0).
Figure 24. CLKinX/X* Single-Ended Termination
If the CLKin pins are being driven with a single-ended LVCMOS/LVTTL source, either DC coupling or AC
coupling may be used. If DC coupling is used, the CLKinX_BUF_TYPE should be set to MOS buffer mode
(CLKinX_BUF_TYPE = 1) and the voltage swing of the source must meet the specifications for DC coupled,
MOS-mode clock inputs given in the table of Electrical Characteristics. If AC coupling is used, the
CLKinX_BUF_TYPE should be set to the bipolar buffer mode (CLKinX_BUF_TYPE = 0). The voltage swing at
the input pins must meet the specifications for AC coupled, bipolar mode clock inputs given in the table of
Electrical Characteristics. In this case, some attenuation of the clock input level may be required. A simple
resistive divider circuit before the AC coupling capacitor is sufficient.
Figure 25. DC Coupled LVCMOS/LVTTL Reference Clock
CLKoutX
CLKoutX*
LVPECL
Receiver
50:
100:Trace
(Differential)
50:
Vcc - 2 V
Vcc - 2 V
LVPECL
Driver
CLKoutX
CLKoutX*
LVDS
Receiver
100:
100:Trace
(Differential)
LVDS
Driver
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Application Information (continued)
9.1.3 Termination and Use of Clock Output (Drivers)
When terminating clock drivers keep in mind these guidelines for optimum phase noise and jitter performance:
Transmission line theory should be followed for good impedance matching to prevent reflections.
Clock drivers should be presented with the proper loads. For example:
LVDS drivers are current drivers and require a closed current loop.
LVPECL drivers are open emitters and require a DC path to ground.
Receivers should be presented with a signal biased to their specified DC bias level (common mode voltage)
for proper operation. Some receivers have self-biasing inputs that automatically bias to the proper voltage
level. In this case, the signal should normally be AC coupled.
It is possible to drive a non-LVPECL or non-LVDS receiver with an LVDS or LVPECL driver as long as the above
guidelines are followed. Check the datasheet of the receiver or input being driven to determine the best
termination and coupling method to be sure that the receiver is biased at its optimum DC voltage (common mode
voltage). For example, when driving the OSCin/OSCin* input of the LMK04906 family, OSCin/OSCin* should be
AC coupled because OSCin/OSCin* biases the signal to the proper DC level (See Figure 39) This is only slightly
different from the AC coupled cases described in Driving CLKin Pins With a Single-Ended Source because the
DC blocking capacitors are placed between the termination and the OSCin/OSCin* pins, but the concept remains
the same. The receiver (OSCin/OSCin*) sets the input to the optimum DC bias voltage (common mode voltage),
not the driver.
9.1.3.1 Termination for DC Coupled Differential Operation
For DC coupled operation of an LVDS driver, terminate with 100 Ωas close as possible to the LVDS receiver as
shown in Figure 26.
Figure 26. Differential LVDS Operation, DC Coupling, No Biasing of the Receiver
For DC coupled operation of an LVPECL driver, terminate with 50 Ωto VCC 2 V as shown in Figure 27.
Alternatively terminate with a Thevenin equivalent circuit (120-Ωresistor connected to VCC and an 82-Ωresistor
connected to ground with the driver connected to the junction of the 120-Ωand 82-Ωresistors) as shown in
Figure 28 for VCC = 3.3 V.
Figure 27. Differential LVPECL Operation, DC Coupling
0.1 PF
0.1 PF
LVDS
Receiver
100:Trace
(Differential)
LVDS
Driver
100:
CLKoutX
CLKoutX*
0.1 PF
0.1 PF
LVDS
Receiver
50:
100:Trace
(Differential)
LVDS
Driver
50:
Vbias
CLKoutX
CLKoutX*
LVPECL
Receiver
120:
100:Trace
(Differential)
120:
Vcc
Vcc
LVPECL
Driver
82:82:
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Application Information (continued)
Figure 28. Differential LVPECL Operation, DC Coupling, Thevenin Equivalent
9.1.3.2 Termination for AC Coupled Differential Operation
AC coupling allows for shifting the DC bias level (common mode voltage) when driving different receiver
standards. Since AC coupling prevents the driver from providing a DC bias voltage at the receiver it is important
to ensure the receiver is biased to its ideal DC level.
When driving non-biased LVDS receivers with an LVDS driver, the signal may be AC coupled by adding DC
blocking capacitors; however, the proper DC bias point needs to be established at the receiver. One way to do
this is with the termination circuitry in Figure 29.
Figure 29. Differential LVDS Operation, AC Coupling, External Biasing at the Receiver
Some LVDS receivers may have internal biasing on the inputs. In this case, the circuit shown in Figure 29 is
modified by replacing the 50-Ωterminations to Vbias with a single 100-Ωresistor across the input pins of the
receiver, as shown in Figure 30. When using AC coupling with LVDS outputs, there may be a start-up delay
observed in the clock output due to capacitor charging. The previous figures employ a 0.1-µF capacitor. This
value may need to be adjusted to meet the start-up requirements for a particular application.
Figure 30. LVDS Termination for a Self-Biased Receiver
CLKoutX
CLKoutX* 50:
50:Trace
50:
Load
Vcc - 2V
Vcc - 2V
LVPECL
Driver
CLKoutX
CLKoutX*
120:120:
0.1 PF
0.1 PFLVPECL
Receiver
100:Trace
(Differential)
LVPECL
Driver
82:
120:
Vcc
82:
120:
Vcc
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Application Information (continued)
LVPECL drivers require a DC path to ground. When AC coupling an LVPECL signal use 120-Ωemitter resistors
close to the LVPECL driver to provide a DC path to ground as shown in Figure 31. For proper receiver operation,
the signal should be biased to the DC bias level (common mode voltage) specified by the receiver. The typical
DC bias voltage for LVPECL receivers is 2 V. A Thevenin equivalent circuit (82-Ωresistor connected to VCC and
a 120-Ωresistor connected to ground with the driver connected to the junction of the 82-Ωand 120-Ωresistors)
is a valid termination as shown in Figure 31 for VCC = 3.3 V. Note this Thevenin circuit is different from the DC
coupled example in Figure 28.
Figure 31. Differential LVPECL Operation, AC Coupling, Thevenin Equivalent, External Biasing at the
Receiver
9.1.3.3 Termination for Single-Ended Operation
A balun can be used with either LVDS or LVPECL drivers to convert the balanced, differential signal into an
unbalanced, single-ended signal.
It is possible to use an LVPECL driver as one or two separate 800 mVpp signals. When using only one LVPECL
driver of a CLKoutX/CLKoutX* pair, be sure to properly terminated the unused driver. When DC coupling one of
the LMK04906 family clock LVPECL drivers, the termination should be 50 Ωto VCC 2 V as shown in Figure 32.
The Thevenin equivalent circuit is also a valid termination as shown in Figure 33 for Vcc = 3.3 V.
Figure 32. Single-Ended LVPECL Operation, DC Coupling
CLKoutX
CLKoutX*
120:
120:
0.1 PF
0.1 PF
50:Trace
50:
Load
50:
LVPECL
Driver
CLKoutX
CLKoutX*
:
50:Trace
120:
Load
Vcc
82:
120:
Vcc
LVPECL
Driver
82
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Application Information (continued)
Figure 33. Single-Ended LVPECL Operation, DC Coupling, Thevenin Equivalent
When AC coupling an LVPECL driver use a 120 Ωemitter resistor to provide a DC path to ground and ensure a
50-Ωtermination with the proper DC bias level for the receiver. The typical DC bias voltage for LVPECL
receivers is 2 V (See Driving CLKin Pins With a Single-Ended Source). If the companion driver is not used it
should be terminated with either a proper AC or DC termination. This latter example of AC coupling a single-
ended LVPECL signal can be used to measure single-ended LVPECL performance using a spectrum analyzer or
phase noise analyzer. When using most RF test equipment no DC bias point (0 VDC) is required for safe and
proper operation. The internal 50 Ωtermination of the test equipment correctly terminates the LVPECL driver
being measured as shown in Figure 34.
Figure 34. Single-Ended LVPECL Operation, AC-Coupling
9.1.4 Frequency Planning With the LMK04906 Family
Calculating the value of the output dividers for use with the LMK04906 family is simple due to the architecture of
the LMK04906. That is, the VCO divider may be bypassed and the clock output dividers allow for even and odd
output divide values from 2 to 1045. For most applications it is recommended to bypass the VCO divider.
The procedure for determining the needed LMK04906 device and clock output divider values for a set of clock
output frequencies is straightforward.
1. Calculate the least common multiple (LCM) of the clock output frequencies.
2. Determine which VCO ranges will support the target clock output frequencies given the LCM.
3. Determine the clock output divide values based on VCO frequency.
4. Determine the PLL2 reference frequency doubler mode and PLL2_P, PLL2_N, and PLL2_R divider values
given the OSCin VCXO or crystal frequency and VCO frequency.
For example, given the following target output frequencies: 200 MHz, 120 MHz, and 25 MHz with a VCXO
frequency of 40 MHz:
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Application Information (continued)
First determine the LCM of the three frequencies. LCM(200 MHz, 120 MHz, 25 MHz) = 600 MHz. The LCM
frequency is the lowest frequency for which all of the target output frequencies are integer divisors of the LCM.
Note, if there is one frequency which causes the LCM to be very large, greater than 3 GHz for example,
determine if there is a single frequency requirement which causes this. It may be possible to select the
VCXO/crystal frequency to satisfy this frequency requirement through OSCout or CLKout3/4 driven by OSCin. In
this way it is possible to get non-integer related frequencies at the outputs.
Second, since the LCM is not in a VCO frequency range supported by the LMK04906, multiply the LCM
frequency by an integer which causes it to fall into a valid VCO frequency range of an LMK04906 device. In this
case 600 MHz * 4 = 2400 MHz which is valid for the LMK04906.
Third, continuing the example by using a VCO frequency of 2400 MHz and the LMK04906, the CLKout dividers
can be calculated by simply dividing the VCO frequency by the output frequency. To output 200 MHz, 120 MHz,
and 25 MHz the output dividers will be 12, 20, and 96 respectively.
2400 MHz / 200 MHz = 12
2400 MHz / 120 MHz = 20
2400 MHz / 25 MHz = 96
Fourth, PLL2 must be locked to its input reference. See PLL Programming for more information on this topic. By
programming the clock output dividers and the PLL2 dividers the VCO can lock to the frequency of 2400 MHz
and the clock outputs dividers will each divide the VCO frequency down to the target output frequencies of 200
MHz, 120 MHz, and 25 MHz.
NOTE
Refer to application note AN-1865 Frequency Synthesis and Planning for PLL
Architectures for more information on this topic and LCM calculations.
9.1.5 PLL Programming
To lock a PLL the divided reference and divided feedback from VCO or VCXO must result in the same phase
detector frequency. The tables below illustrate how the divides are structured for the reference path (R) and
feedback path (N) depending on the MODE of the device.
Table 110. PLL1 Phase Detector Frequency Reference Path (R)
MODE (R) PLL1 PDF =
All CLKinX Frequency / CLKinX_PreR_DIV / PLL1_R
(1) The actual CLKoutX_DIV used is selected by FEEDBACK_MUX.
Table 111. PLL1 Phase Detector Frequency Feedback Path (N)
MODE VCO_MUX OSCout0 PLL1 PDF (N) =
Internal VCO Dual PLL Bypass VCXO Frequency / PLL1_N
Divided VCXO Frequency / OSCin_DIV / PLL1_N
Internal VCO /w 0-delay Bypass VCO Frequency / CLKoutX_DIV / PLL1_N (1)
Divided VCO Frequency / VCO_DIV / CLKoutX_DIV / PLL1_N (1)
(1) For applications in which the OSCin frequency and PLL2 phase detector frequency are equal, the best PLL2 in-band noise can be
achieved when the doubler is enabled (EN_PLL2_REF_2X = 1) and the PLL2 R divide value is 2. Do not use doubler disabled
(EN_PLL2_REF_2X = 0) and PLL2 R divide value of 1.
Table 112. PLL2 Phase Detector Frequency Reference Path (R)
EN_PLL2_REF_2X PLL2 PDF (R) =
Disabled OSCin Frequency / PLL2_R (1)
Enabled OSCin Frequency * 2 / PLL2_R (1)
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Table 113. PLL2 Phase Detector Frequency Feedback Path (N)
MODE VCO_MUX PLL2 PDF (N) =
Dual PLL VCO VCO Frequency / PLL2_P / PLL2_NDual PLL /w 0-delay
Single PLL
Dual PLL VCO Divider VCO Frequency / VCO_DIV / PLL2_P / PLL2_NDual PLL /w 0-delay
Single PLL
Dual PLL External VCO VCO Frequency / VCO_DIV / PLL2_P / PLL2_N
Dual PLL External VCO /w 0-delay
Single PLL /w 0-delay VCO VCO Frequency / CLKoutX_DIV / PLL2_N
VCO Divider VCO Frequency / VCO_DIV / CLKoutX_DIV / PLL2_N
Table 114. PLL2 Phase Detector Frequency Feedback Path (N) during VCO Frequency Calibration
MODE VCO_MUX PLL2 PDF (N_CAL) =
All Internal VCO Modes VCO VCO Frequency / PLL2_P / PLL2_N_CAL
VCO Divider VCO Frequency / VCO_DIV / PLL2_P / PLL2_N_CAL
(1) For applications in which the OSCin frequency and PLL2 phase detector frequency are equal, the best PLL2 in-band noise can be
achieved when the doubler is enabled (EN_PLL2_REF_2X = 1) and the PLL2 R divide value is 2. Do not use doubler disabled
(EN_PLL2_REF_2X = 0) and PLL2 R divide value of 1.
9.1.5.1 Example PLL2 N Divider Programming
To program PLL2 to lock an LMK04906 using Dual PLL mode to a VCO frequency of 2400 MHz using a 40 MHz
VCXO reference, first determine the total PLL2 N divide value. This is VCO Frequency / PLL2 phase detector
frequency. This example assumes the PLL2 reference frequency doubler is enabled and a PLL2 R divider value
of 2 (1) which results in PLL2 R divide value of 1 which results in PLL2 phase detector frequency the same as
PLL2 reference frequency (40 MHz). 2400 MHz / 40 MHz = 60, so the total PLL2 N divide value is 60.
The dividers in the PLL2 N feedback path for Dual PLL mode include PLL2_P and PLL2_N. PLL2_P can be
programmed from 2 to 8 even and odd. PLL2_N can be programmed from 1 to 263,143 even and odd. Since the
total PLL2 N divide value of 60 contains the factors 2, 2, 3, and 5, it would be allowable to program PLL2_P to 2,
3 or 5. It is simplest to use the smallest divide, so PLL2_P = 2, and PLL2_N = 30 which results in a Total PLL2 N
= 60.
For this example and in most cases, PLL2_N_CAL will have the same value as PLL2_N. However when using
Single PLL mode with 0-delay, the values will differ. When using an external VCO, PLL2_N_CAL value is
unused.
9.1.6 Digital Lock Detect Frequency Accuracy
The digital lock detect circuit is used to determine PLL1 locked, PLL2 locked, and holdover exit events. A window
size and lock count register are programmed to set a ppm frequency accuracy of reference to feedback signals
of the PLL for each event to occur. When a PLL digital lock event occurs the PLL's digital lock detect is asserted
true. When the holdover exit event occurs, the device will exit holdover mode.
EVENT PLL WINDOW SIZE LOCK COUNT
PLL1 Locked PLL1 PLL1_WND_SIZE PLL1_DLD_CNT
PLL2 Locked PLL2 PLL2_WND_SIZE PLL2_DLD_CNT
Holdover exit PLL1 PLL1_WND_SIZE HOLDOVER_DLD_CNT
For a digital lock detect event to occur there must be a “lock count” number of phase detector cycles of PLLX
during which the time/phase error of the PLLX_R reference and PLLX_N feedback signal edges are within the
user programmable "window size." Since there must be at least "lock count" phase detector events before a lock
event occurs, a minimum digital lock event time can be calculated as "lock count" / fPDX where X = 1 for PLL1 or
2 for PLL2.
16
¨
©
§¸
¹
·
0 digital delay = CLKoutX_DIV x CLKoutX_DIV
+ 0.5 - 11.5
¸
¹
·
¨
©
§«
«
ª
¬
«
«
ª
¬
1e6 PLLX_WND_SIZE f
x x PDX
PLLX_DLD_CNT
ppm =
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By using Equation 4, values for a lock count and window size can be chosen to set the frequency accuracy
required by the system in ppm before the digital lock detect event occurs:
(4)
The effect of the lock count value is that it shortens the effective lock window size by dividing the window size by
lock count.
If at any time the PLLX_R reference and PLLX_N feedback signals are outside the time window set by window
size, then the lock count value is reset to 0.
9.1.6.1 Minimum Lock Time Calculation Example
To calculate the minimum PLL2 digital lock time given a PLL2 phase detector frequency of 40 MHz and
PLL2_DLD_CNT = 10,000. Then the minimum lock time of PLL2 will be 10,000 / 40 MHz = 250 µs.
9.1.7 Calculating Dynamic Digital Delay Values For Any Divide
This section explains how to calculate the dynamic digital delay for any divide value.
Dynamic digital delay allows the time offset between two or more clock outputs to be adjusted with no or minimal
interruption of clock outputs. Since the clock outputs are operating at a known frequency, the time offset can also
be expressed as a phase shift. When dynamically adjusting the digital delay of clock outputs with different
frequencies the phase shift should be expressed in terms of the higher frequency clock. The step size of the
smallest time adjustment possible is equal to half the period of the Clock Distribution Path, which is the VCO
frequency (Equation 2) or the VCO frequency divided by the VCO divider (Equation 3) if not bypassed. The
smallest degree phase adjustment with respect to a clock frequency will be 360 * the smallest time adjustment *
the clock frequency. The total number of phase offsets that the LMK04906 family is able to achieve using
dynamic digital delay is equal 1 / (higher clock frequency * the smallest phase adjustment).
Equation 5 calculates the digital delay value that must be programmed for a synchronizing clock to achieve a 0
time/phase offset from the qualifying clock. Once this digital delay value is known, it is possible to calculate the
digital delay value for any phase offset. The qualifying clock for dynamic digital delay is selected by the
FEEDBACK_MUX. When dynamic digital delay is engaged with same clock output used for the qualifying clock
and the new synchronized clock, it is termed relative dynamic digital delay since causing another SYNC event
with the same digital delay value will offset the clock by the same phase once again. The important part of
relative dynamic digital delay is that the CLKoutX_HS must be programmed correctly when the SYNC event
occurs (Table 6). This can result in needing to program the device twice. Once to set the new CLKoutX_DDLY
with CLKoutX_HS as required for the SYNC event, and again to set the CLKoutX_HS to its desired value.
Digital delay values are programmed using the CLKoutX_DDLY and CLKoutX_HS registers as shown in
Equation 6. For example, to achieve a digital delay of 13.5, program CLKoutX_DDLY = 14 and CLKoutX_HS = 1.
(5)
Equation 5 uses the ceiling operator. To find the ceiling of a fractional number round up. An integer remains the
same value.
Digital delay = CLKoutX_DDLY - (0.5 * CLKoutX_HS) (6)
Note: since the digital delay value for 0 time/phase offset is a function of the qualifying clock's divide value, the
resulting digital delay value can be used for any clock output operating at any frequency to achieve a 0
time/phase offset from the qualifying clock. Therefore the calculated time shift table will also be the same as in
Table 115
9.1.7.1 Example
Consider a system with:
A VCO frequency of 2000 MHz.
The VCO divider is bypassed, therefore the clock distribution path frequency is 2000 MHz.
CLKout0_DIV = 10 resulting in a 200 MHz frequency on CLKout0.
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CLKout2_DIV = 20 resulting in a 100 MHz frequency on CLKout2.
For this system the minimum time adjustment is 0.25 ns, which is 0.5 / (2000 MHz). Since the higher frequency
is 200 MHz, phase adjustments will be calculated with respect to the 200 MHz frequency. The 0.25 ns minimum
time adjustment results in a minimum phase adjustment of 18 degrees, which is 360 degrees / 200 MHz * 0.25
ns.
To calculate the digital delay value to achieve a 0 time/phase shift of CLKout2 when CLKout0 is the qualifying
clock. Solve Equation 5 using the divide value of 10. To solve the equation 16/10 = 1.6, the ceiling of 1.6 is 2.
Then to finish solving the equation solve (2 + 0.5) * 10 - 11.5 = 13.5. A digital delay value of 13.5 is programmed
by setting CLKout2_DDLY = 14 and CLKout2_HS = 1.
To calculate the digital delay value to achieve a 0 time/phase shift of CLKout0 when CLKout2 is the qualifying
clock, solve Equation 5 using the divide value of CLKout2, which is 20. This results in a digital delay of 18.5
which is programmed as CLKout0_DDLY = 19 and CLKout0_HS = 1.
Once the 0 time/phase shift digital delay programming value is known a table can be constructed with the digital
delay value to be programmed for any time/phase offset by decrementing or incrementing the digital delay value
by 0.5 for the minimum time/phase adjustment.
A complete filled out table for use of CLKout0 as the qualifying clock is shown in Table 115. It was created by
entering a digital delay of 13.5 for 0 degree phase shift, then decrementing the digital delay down to the minimum
value of 4.5. Since this did not result in all the possible phase shifts, the digital delay was then incremented from
13.5 to 14.0 to complete all possible phase shifts.
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Table 115. Example Digital Delay Calculation
DIGITAL DELAY CALCULATED TIME SHIFT
(ns)
RELATIVE TIME SHIFT TO 200
MHz
(ns)
PHASE SHIFT OF 200 MHZ
(DEGREES)
4.5 –4.5 0.5 36
5 4.25 0.75 54
5.5 –4 1 72
6 3.75 1.25 90
6.5 –3.5 1.5 108
7 –3.25 1.75 126
7.5 –3 2 144
8 –2.75 2.25 162
8.5 –2.5 2.5 180
9 –2.25 2.75 198
9.5 –2 3 216
10 –1.75 3.25 234
10.5 –1.5 3.5 252
11 –1.25 3.75 270
11.5 –1 4 288
12 –0.75 4.25 306
12.5 –0.5 4.5 324
13 –0.25 4.75 342
13.5 0 0 0
14 0.25 0.25 18
14.5 0.5 0.5 36
Observe that the digital delay value of 4.5 and 14.5 will achieve the same relative time shift/phase delay.
However programming a digital delay of 14.5 will result in a clock off time for the synchronizing clock to achieve
the same phase time shift/phase delay.
Digital delay value is programmed as CLKoutX_DDLY (0.5 × CLKoutX_HS). So to achieve a digital delay of
13.5, program CLKoutX_DDLY = 14 and CLKoutX_HS = 1. To achieve a digital delay of 14, program
CLKoutX_DDLY = 14 and CLKoutX_HS = 0.
9.1.8 Optional Crystal Oscillator Implementation (OSCin/OSCin*)
The LMK04906 family features supporting circuitry for a discretely implemented oscillator driving the OSCin port
pins. Figure 35 illustrates a reference design circuit for a crystal oscillator:
2
CSTRAY
CL = CTUNE + CIN +
CPout1
LMK04906
OSCin
OSCin*
PLL1 Loop Filter
XTAL
CC1 = 2.2 nF
CC2 = 2.2 nF
R1 = 4.7k
R3 = 10k
1 nF
R2 = 4.7k
SMV1249-074LF
Copt
Copt
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Figure 35. Reference Design Circuit for Crystal Oscillator Option
This circuit topology represents a parallel resonant mode oscillator design. When selecting a crystal for parallel
resonance, the total load capacitance, CL, must be specified. The load capacitance is the sum of the tuning
capacitance (CTUNE), the capacitance seen looking into the OSCin port (CIN), and stray capacitance due to PCB
parasitics (CSTRAY), and is given by Equation 7.
(7)
CTUNE is provided by the varactor diode shown in Figure 35, Skyworks model SMV1249-074LF. A dual diode
package with common cathode provides the variable capacitance for tuning. The single diode capacitance
ranges from approximately 31 pF at 0.3 V to 3.4 pF at 3 V. The capacitance range of the dual package (anode to
anode) is approximately 15.5 pF at 3 V to 1.7 pF at 0.3 V. The desired value of VTUNE applied to the diode should
be VCC/2, or 1.65 V for VCC = 3.3 V. The typical performance curve from the data sheet for the SMV1249-074LF
indicates that the capacitance at this voltage is approximately 6 pF (12 pF / 2).
The nominal input capacitance (CIN) of the LMK04906 family OSCin pins is 6 pF. The stray capacitance (CSTRAY)
of the PCB should be minimized by arranging the oscillator circuit layout to achieve trace lengths as short as
possible and as narrow as possible trace width (50-Ωcharacteristic impedance is not required). As an example,
assume that CSTRAY is 4 pF. The total load capacitance is nominally:
1
(C0 + CL1)-1
(C0 + CL2)=2
1À
FFCL1
FCL1 - FCL2 =2À
C1
=
F
'FC0
C1¸
¹
·
¨
©
§CL2
C1
+
1
-
C0
C1¸
¹
·
¨
©
§CL1
C1
+
1
2(C0 + CL1)+ 1 C0
C1¸
¹
·
¨
©
§CL
C1
+
1+ 1
2
C1
FL = FS À = FS À
2
CL = 6 + 6 + 4= 14 pF
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(8)
Consequently the load capacitance specification for the crystal in this case should be nominally 14 pF.
The 2.2-nF capacitors shown in the circuit are coupling capacitors that block the DC tuning voltage applied by
the 4.7-kand 10-kresistors. The value of these coupling capacitors should be large, relative to the value of
CTUNE (CC1 = CC2 >> CTUNE), so that CTUNE becomes the dominant capacitance.
For a specific value of CL, the corresponding resonant frequency (FL) of the parallel resonant mode circuit is:
where
FS= Series resonant frequency
C1= Motional capacitance of the crystal
CL= Load capacitance
C0= Shunt capacitance of the crystal, specified on the crystal datasheet (9)
The normalized tuning range of the circuit is closely approximated by:
(10)
CL1, CL2 = The endpoints of the circuit’s load capacitance range, assuming a variable capacitance element is one
component of the load. FCL1, FCL2 = parallel resonant frequencies at the extremes of the circuit’s load
capacitance range.
A common range for the pullability ratio, C0/C1, is 250 to 280. The ratio of the load capacitance to the shunt
capacitance is approximately (n × 1000), n < 10. Hence, picking a crystal with a smaller pullability ratio supports
a wider tuning range because this allows the scale factors related to the load capacitance to dominate.
Examples of the phase noise and jitter performance of the LMK04906 with a crystal oscillator are shown in
Table 116. This table illustrates the clock output phase noise when a 20.48-MHz crystal is paired with PLL1.
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(1) Performance data and crystal specifications contained in this section are based on Vectron model VXB1-1150-20M480, 20.48 MHz.
PLL1 has a narrow loop bandwidth, PLL2 loop parameters are: C1 = 150 pF, C2 = 120 nF, R2 = 470 , Charge Pump current = 3.2 mA,
Phase detector frequency = 20.48 MHz or 40.96 MHz, VCO frequency = 2949.12 MHz. Loop filter was optimized for 40.96-MHz phase
detector performance.
Table 116. Example RMS Jitter and Clock Output Phase Noise for LMK04906 With a
20.48-MHz Crystal Driving OSCin (T = 25 °C, VCC = 3.3 V) (1)
INTEGRATION
BANDWIDTH CLOCK OUTPUT TYPE
PLL2 PDF = 20.48 MHz
(EN_PLL2_REF2X = 0,
XTAL_LVL = 3)
PLL2 PDF = 40.96 MHz
(EN_PLL2_REF2X = 1, XTAL_LVL = 3)
fCLK = 245.76 MHz fCLK = 122.88 MHz fCLK = 245.76 MHz
RMS JITTER (ps)
100 Hz 20 MHz LVCMOS 374 412 382
LVDS 419 421 372
LVPECL 1.6 Vpp 460 448 440
10 kHz 20 MHz LVCMOS 226 195 190
LVDS 231 205 194
LVPECL 1.6 Vpp 226 191 188
PHASE NOISE (dBc/Hz)
Offset Clock Output Type
PLL2 PDF = 20.48 MHz
(EN_PLL2_REF2X = 0,
XTAL_LVL = 3) PLL2 PDF = 40.96 MHz
(EN_PLL2_REF2X = 1, XTAL_LVL = 3)
fCLK = 245.76 MHz fCLK = 122.88 MHz fCLK = 245.76 MHz
100 Hz LVCMOS -87 -93 -87
LVDS -86 -91 -86
LVPECL 1.6 Vpp -86 -92 -85
1 kHz LVCMOS -115 -121 -115
LVDS -115 -123 -116
LVPECL 1.6 Vpp -114 -122 -116
10 kHz LVCMOS -117 -128 -122
LVDS -117 -128 -122
LVPECL 1.6 Vpp -117 -128 -122
100 kHz LVCMOS -130 -135 -129
LVDS -130 -135 -129
LVPECL 1.6 Vpp -129 -135 -129
1 MHz LVCMOS -150 -154 -148
LVDS -149 -153 -148
LVPECL 1.6 Vpp -150 -154 -148
40 MHz LVCMOS -159 -162 -159
LVDS -157 -159 -157
LVPECL 1.6 Vpp -159 -161 -159
Example crystal specifications are presented in Table 117.
Table 117. Example Crystal Specifications
PARAMETER VALUE
Nominal Frequency (MHz) 20.48
Frequency Stability, T = 25 °C ± 10 ppm
Operating temperature range -40 °C to +85 °C
Frequency Stability, -40 °C to +85 °C ± 15 ppm
Load Capacitance 14 pF
Shunt Capacitance (C0) 5 pF Maximum
Motional Capacitance (C1) 20 fF ± 30%
'V À 106
FNOM À ('ppm2 - 'ppm1)
KVCO =
= 0.00164 MHz
V
2.03 - 0.814
0.001 - (-0.001)
KVCO = 'F
'V,MHz
V
=¸
¹
·
¨
©
§'F2 - 'F1
VTUNE2 - VTUNE1
0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2
-180
-140
-100
-60
-20
20
60
100
140
180
PPM
VTUNE(V)
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Table 117. Example Crystal Specifications (continued)
PARAMETER VALUE
Equivalent Series Resistance 25 ΩMaximum
Drive level 2 mWatts Maximum
C0/C1ratio 225 typical, 250 Maximum
See Figure 36 for a representative tuning curve.
Figure 36. Example Tuning Curve, 20.48-MHz Crystal
The tuning curve achieved in the user's application may differ from the curve shown above due to differences in
PCB layout and component selection.
This data is measured on the bench with the crystal integrated with the LMK04906 family. Using a voltmeter to
monitor the VTUNE node for the crystal, the PLL1 reference clock input frequency is swept in frequency and the
resulting tuning voltage generated by PLL1 is measured at each frequency. At each value of the reference clock
frequency, the lock state of PLL1 should be monitored to ensure that the tuning voltage applied to the crystal is
valid.
The curve shows over the tuning voltage range of 0.3 VDC to 3.0 VDC, the frequency range is –140 to 91 ppm;
or equivalently, a tuning range of –2850 Hz to 1850 Hz. The measured tuning voltage at the nominal crystal
frequency (20.48 MHz) is 1.7 V. Using the diode data sheet tuning characteristics, this voltage results in a tuning
capacitance of approximately 6.5 pF.
The tuning curve data can be used to calculate the gain of the oscillator (KVCO). The data used in the calculations
is taken from the most linear portion of the curve, a region centered on the crossover point at the nominal
frequency (20.48 MHz). For a well designed circuit, this is the most likely operating range. In this case, the tuning
range used for the calculations is ± 1000 Hz 0.001 MHz), or ± 81.4 ppm. The simplest method is to calculate
the ratio:
(11)
ΔF2 and ΔF1 are in units of MHz. Using data from the curve this becomes:
(12)
A second method uses the tuning data in units of ppm:
(13)
FNOM is the nominal frequency of the crystal and is in units of MHz. Using the data, this becomes:
R
CLKinX
CLKinX*
N
Phase
Detector
PLL1
External VCXO
or Tunable
Crystal
R
N
Phase
Detector
PLL2 Internal
VCO
External
Loop Filter
OSCin
CPout1
OSCout0
OSCout0*
LMK04906
CPout2
Partially
Integrated
Loop Filter
6 outputs
External
Loop Filter
PLL1 PLL2
6 blocks
1 output
3 inputs
Input
Buffer CLKoutX
CLKoutX*
Divider
Digital Delay
Analog Delay
Copyright © 2016, Texas Instruments Incorporated
= 0.00164, MHz
V
(2.03 - 0.814) À 106
12.288 À 81.4 - (-81.4)
( )
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(14)
In order to ensure startup of the oscillator circuit, the equivalent series resistance (ESR) of the selected crystal
should conform to the specifications listed in Electrical Characteristics.
It is also important to select a crystal with adequate power dissipation capability, or drive level. If the drive level
supplied by the oscillator exceeds the maximum specified by the crystal manufacturer, the crystal will undergo
excessive aging and possibly become damaged. Drive level is directly proportional to resonant frequency,
capacitive load seen by the crystal, voltage and equivalent series resistance (ESR). For more complete coverage
of crystal oscillator design, see AN-1939 Crystal Based Oscillator Design with the LMK04000 Family (SNAA065).
9.2 Typical Application
Normal use case of the LMK04906 device is as a dual loop jitter cleaner. This section will discuss a design
example to illustrate the various functional aspects of the LMK04906 device.
Figure 37. Simplified Functional Block Diagram for Dual Loop Mode
9.2.1 Design Requirements
Given a remote radio head (RRU) type application which needs to clock some ADCs, DACs, FPGA, SERDES,
and an LO. The input clock will be a recovered clock which needs jitter cleaning. The FPGA clock should have a
clock output on power up. A summary of clock input and output requirements are as follows:
Clock Input:
30.72 MHz recovered clock.
Clock Outputs:
2x 245.76 MHz clock for ADC, LVPECL
4x 983.04 MHz clock for DAC, LVPECL
1x 122.88 MHz clock for FPGA, LVPECL. POR clock
1x 122.88 MHz clock for SERDES, LVPECL
2x 122.88 MHz clock for LO, LVCMOS
It is also desirable to have the holdover feature engage if the recovered clock reference is ever lost. The
following information reviews the steps to produce this design.
9.2.2 Detailed Design Procedure
Design of all aspects of the LMK04906 are quite involved and software has been written to assist in part
selection, part programming, loop filter design, and simulation. This design procedure will give a quick outline of
the process.
Note that this information is current as of the date of the release of this datasheet. Design tools receive
continuous improvements to add features and improve model accuracy. Refer to software instructions or training
for latest features.
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Typical Application (continued)
1. Device Selection
the key to device selection is required VCO frequency given required output frequencies. The device
must be able to produce the VCO frequency that can be divided down to required output frequencies.
The software design tools will take inot account VCO frequency range for specific devices based on the
application's required output frequencies. Using an external VCO provides increased flexibility regarding
valid designs.
To understand the process better, refer to Frequency Planning With the LMK04906 Family for more detail
on calculating valid VCO frequency when using integer dividers using the least common multiple (LCM) of
the output frequencies.
2. Device Configuration
There are many possible permutations of dividers and other registers to get same input and output
frequencies from a device. However there are some optimizations and trade-offs to be considered.
If more than one divider is in series, for instance VCO divider to CLKout divider, or VCO divider to PLL
prescaler to PLL N. It is possible although not assured that some crosstalk/mixing could be created
when using some divides.
The design software normally attempts to maximize phase detector frequency, use smallest dividers, and
maximizes PLL charge pump current.
When an external VCXO or crystal is used for jitter cleaning, the design software will choose the
maximum frequency value, depending on design software options, this max frequency may be limited to
standard value VCXOs/Crystals. Note, depending on application, different frequency VCXOs may be
chosen to generate some of the required output frequencies.
Refer to PLL Programming for divider equations need to ensure PLL is locked. The design software is
able to configure the device for most cases, but at this time for advanced features like 0-delay, the
user must take care to ensure proper PLL programming.
These guidelines may be followed when configuring PLL related dividers or other related registers:
For lowest possible in-band PLL flat noise, maximize phase detector frequency to minimize N divide
value.
For lowest possible in-band PLL flat noise, maximize charge pump current. The highest value charge
pump currents often have similar performance due to diminishing returns.
To reduce loop filter component sizes, increase N value and/or reduce charge pump current.
Large capacitors help reduce phase detector spurs at phase detector frequency caused by external
VCOs/VCXOs with low input impedance.
As rule of thumb, keeping the phase detector frequency approximately between 10 * PLL loop
bandwidth and 100 * PLL loop bandwidth. A phase detector frequency less than 5 * PLL bandwidth
may be unstable and a phase detector frequency > 100 * loop bandwidth may experience increased
lock time due to cycle slipping.
3. PLL Loop Filter Design
It is recommended to use Clock Design Tool or Clock Architect to design your loop filter.
Best loop filter design and simulation can be achieved when:
Custom reference and VCXO phase noise profiles are loaded into the software.
VCO gain of the external VCXO or possible external VCO device are entered.
The Clock Design Tool will return solutions with high reference/phase detector frequencies by default. In
the Clock Design Tool the user may increase the reference divider to reduce the frequency if desired.
Due to the narrow loop bandwidth used on PLL1, it is common to lower the phase detector frequency on
PLL1 to reduce component size.
While designing loop filter, adjusting the charge pump current or N value can help with loop filter
component selection. Lower charge pump currents and larger N values result in smaller component
values but may increase impacts of leakage and reduce PLL phase noise performance.
More detailed understanding of loop filter design can found in Dean Banerjee's PLL Performance,
Simulation, and Design (www.ti.com/tool/pll_book).
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Typical Application (continued)
4. Clock Output Assignment
At this time the design software does not take into account frequency assignment to specific outputs
except to ensure that the output frequencies can be achieved. It is best to consider proximity of each
clock output to each other and other PLL circuitry when choosing final clock output locations. Here are
some guidelines to help achieve best performance when assigning outputs to specific CLKout/OSCout
pins.
Group common frequencies together.
PLL charge pump circuitry can cause crosstalk at charge pump frequency. Place outputs sharing
charge pump frequency or lower priority outputs not sensitive to charge pump frequency spurs
together.
Muxes can create a path for noise coupling. Consider all frequencies which may have some bleed
through from non-selected mux inputs.
For example, LMK04906 CLKout6/7 and CLKout8/9 share a mux with OSCin.
Some clock targets require low close-in phase noise. If possible, use a VCXO based PLL1 output for
such a clock target. An example is a clock to a PLL reference.
Some clock targets require excellent noise floor performance. Outputs driven by the internal VCO have
the best noise floor performance. An example is an ADC or DAC.
5. Other device specific configuration. For LMK04906, consider the following:
PLL lock time based on programming:
In addition to the time it takes the device to lock to frequency, there is a digital filter to avoid false lock
time detects which can also be used to ensure a specific PPM frequency accuracy. This also impacts
the time it takes for the digital lock detect (DLD) pin to be asserted. Refer to Digital Lock Detect
Frequency Accuracy for more information.
Holdover configuration:
Specific PPM frequency accuracy required to exit holdover can be programmed. Refer to Holdover
Mode - Automatic Exit of Holdover for more information.
Digital delay: phase alignment of the output clocks.
Analog delay: another method to shift phases of clocks with finer resolution with the penalty of increase
noise floor. Clock Design Tool can simulate analog delay impact on phase noise floor.
Dynamic digital delay: ability to shift phase alignment of clocks with minimum disruption during operation.
6. Device Programming
The software tool CodeLoader for EVM programming can be used to setup the device in the desired
configuration, then export a hex register map suitable for use in application.
9.2.2.1 Device Selection
Use the WEBENCH Clock Architect Tool or Clock Design Tool. Enter the required frequencies and formats into
the tool. To use this device, find a solution using the LMK04906.
9.2.2.1.1 Clock Architect
When viewing resulting solutions, it is possible to narrow the parts used in the solution by setting a filter.
Under advanced tab, filtering of specific parts can be done using regular expressions in the Part Filter box.
"LMK04906" will filter for only the LMK04906 device (without quotes).
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Typical Application (continued)
9.2.2.1.2 Clock Design Tool
In wizard-mode, select Dual Loop PLL to find the LMK04906 device. If a high frequency and clean reference is
available, Although dual loop mode is selected as a customer requirement, it is not required to use dual loop;
PLL1 can be powered down and input is then provided via the OSCin port. When simulating single loop
solutions, set PLL1 loop filter block to "0 Hz LBW" and use VCXO as the reference block.
9.2.2.1.3 Calculation Using LCM
In this example, the LCM(245.76 MHz, 983.04 MHz, 122.88 MHz) = 983.04 MHz. A valid VCO frequency for
LMK04906 is 2949.12 MHz = 3 * 983.04 MHz. Therefore the LMK0480B may be used to produce these output
frequencies.
9.2.2.2 Device Configuration
The tools automatically configure the simulation to meet the input and output frequency requirements given and
make assumptions about other parameters to give some default simulations. The assumptions made are to
maximize input frequencies, phase detector frequencies, and charge pump currents while minimizing VCO
frequency and divider values.
For this example, when using the clock design tool, the reference would have been manually entered as 30.72
MHz according to input frequency requirements, but the tool allows VCXO1 frequency either to be set manually,
auto-selected according to standard frequencies, or auto-selected for best frequency. With the best frequency
option, the highest possible VCXO frequency which gives the highest possible PLL2 PDF frequency is
recommended first. In this case: 421 + 53/175 MHz VCXO resulting in a 140 + 76/175 MHz phase detector
frequency. This is a high phase detector frequency, but the VCXO is likely going to be a custom order. The
select configuration page just before simulation shows before some different configurations possible with different
VCO divider values. For example, a more common 491.52 MHz frequency provides a 122.88 MHz PDF. This is a
more logical configuration.
From the simulation page of clock design tool, it can be seen that the VCXO frequency of 491.52 MHz is too high
for feedback into the PLL1_N divider. Reducing the VCXO frequency to 245.76 MHz resolves the PLL1_N divider
max input frequency problem. The PLL2 R divider must be updated to 2 so that the VCO of PLL2 is still at
2949.12 MHz.
At this point the design meets all input and output frequency requirements and it is possible to design a loop filter
for system and simulate performance on CLKouts. However, consider also the following:
At this time the clock design tool doesn't assign outputs strategically for jitter, such as PLL1 vs PLL2. If PLL1
output frequency is high enough, it may have improved jitter performance depending on the noise floor and
application required integration range.
The clock design tool does not consider power on reset clocks in the clock requirements or assignments.
The clock design tool simplifies the LMK04906 architecture not showing the mux complexity around
OSCout0/1 and not showing OSCout1. Simulation of OSCout0 is equivalent to OSCout1.
The next section addresses how the user may alter the design when considering these items.
9.2.2.2.1 PLL LO Reference
PLL1 outputs have the best phase noise performance for LO references. As such OSCout0 can be used to
provide the 122.88 MHz LO reference clock. To achieve this with the 245.76 MHz VCXO the OSCout_DIV can
be set to 2 to provide 122.88 MHz at OSCout0. However in the next section it is determined that for the POR
clock, a 122.88 MHz VCXO will be chosen which results not needing to change this parameter.
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Typical Application (continued)
9.2.2.2.2 POR Clock
If OSCout1 is to be used for LVPECL POR 122.88 MHz clock, the POR value of the OSCout_DIV is 1, so a
122.88 MHz VCXO frequency must be chosen. This may be desired anyway since the phase detector frequency
is limited to 122.88 MHz and lower frequency VCXOs tend to cost less. With this change the OSCin frequency
and phase detector frequency are the same, so the doubler must be enabled and the PLL2 R divider
programmed = 2 to follow the rule stated in PLL Programming. Since the clock design tool does not show the
doubler, PLL2_R will still reflect the value 1 one for the simulation purposes.
If LVDS was required for POR clock, a voltage divider could be used to convert from LVPECL to LVDS.
Note: it is possible to set the PLL2 R = 0.5 to simulate the doubler in-case lower frequency VCXOs would like to
be simulated. For example a 61.44 MHz VCXO could be used while retaining a 122.88 MHz phase detector
frequency. However, it would reduce the LO reference frequency and POR clock frequency to 61.44 MHz.
At this time the main design updates have been made to support the POR clock and loop filter design may begin.
9.2.2.3 PLL Loop Filter Design
The PLL structure for the LMK04906 is illustrated in Figure 37.
At this time the user may choose to make adjustments to the simulation tools for more accurate simulations to
their application. For example:
Clock Design Tool allows loading a custom phase noise plot for any block. Typically, a custom phase noise
plot is entered for CLKin to match the reference phase noise to the device; a phase noise plot for the VCXO
can additionally be provided to match the performance of VCXO used. For improved accuracy in simulation
and optimum loop filter design, be sure to load these custom noise profiles for use in application. After
loading a phase noise plot, user should recalculate the recommended loop filter design.
The Clock Design Tool will return solutions with high reference/phase detector frequencies by default. In the
Clock Design Tool the user may increase the reference divider to reduce the frequency if desired. Due to the
narrow loop bandwidth used on PLL1, it is common to reduce the phase detector frequency on PLL1 by
increasing PLL1 R.
For this example, for PLL1 to perform jitter cleaning and to minimize jitter from PLL2 used for frequency
multiplication:
PLL1: A narrow loop bandwidth PLL1 filter was design by updating the loop bandwidth to 50 Hz and phase
margin to 50 degrees.
PLL2:
VCXO noise profile is measured, then loaded into VCXO block in clock design tool.
The recommended loop filter is redesigned. Updates to the PLL1 loop filter and VCXO phase noise may
change the loop filter recommendation.
The next two sections will discuss PLL1 and PLL2 loop filter design specific to this example using default phase
noise profiles.
NOTE
Clock Design Tool provides some recommend loop filters upon first load of the simulation.
Anytime PLL related inputs change like an input phase noise, charge pump current,
divider values, and so forth. it is best to re-design the PLL1 loop filter to the recommended
design or your desired parameters. After PLL1, then update the PLL2 loop filter in the
same way to keep the loop filters designed and optimized for the application. Since PLL1
loop filter design may impact PLL2 loop filter design, be sure to update the designs in
order.
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Typical Application (continued)
9.2.2.3.1 PLL1 Loop Filter Design
For this example, in the clock design tool simulator click on the PLL1 loop filter design button, then update the
loop bandwidth for 0.05 kHz and the phase margin for 50 degrees and press calculate. With the 30.72 MHz
phase detector frequency and 1.6 mA charge pump; the designed loop filter's largest capacitor, C2, is 27 µF.
Supposing a goal of < 10 µF; setting PLL1 R = 4 and pressing the calculate again shows that C2 is 6.8 µF.
Suppose that a reduction to < 1 µF is desired, continuing to increase the PLL1 R to 8 resulting in a phase
detector frequency of 3.84 MHz and reducing the charge pump current from 1.6 mA to 0.4 mA and calculating
again shows that C2 is 820 nF. As N was increased and charge pump decreased, this final design has R2 = 12
kΩ. The first design with low N value and high charge pump current result in R2 = 390 Ω. The impact of the
thermal resistance is calculated in the tool. Viewing the simulation of the loop filter with the 12-kΩresistor shows
that the thermal noise in the loop is not impacting performance.
It may be desired to design a 3rd order loop filter for additional attenuation input noise and spurs
With the PLL1 loop filter design complete, PLL2's loop filter is ready to be designed.
9.2.2.3.2 PLL2 Loop Filter Design
In the clock design tool simulator, click on the PLL2 loop filter design button, then press recommend design. For
PLL2's loop filter maximum phase detector frequency and maximum charge pump current are typically used.
Typically the jitter integration bandwidth includes the loop filter bandwidth for PLL2. The recommended loop filter
by the tools are designed to minimize jitter. The integrated loop filter components are minimized with this
recommendation as to allow maximum flexibility in achieve wide loop bandwidths for low PLL noise. With the
recommended loop filter calculated, this loop filter is ready to be simulated.
If using integrated components is desired, open the bode plot for the PLL2 Loop Filter, then make adjustments to
the integrated components. The effective loop bandwidth and phase margin with these updates is calculated.
The integrated loop filter components are good to use when attempting to eliminate some spurs since they
provide filtering after the bond wires. The recommended procedure is to increase C3/C4 capacitance, then
R3/R4 resistance. Large R3/R4 resistance can result in degraded VCO phase noise performance.
9.2.2.4 Clock Output Assignment
At this time the Clock Design Tool and Clock Architect only assign outputs to specific clock outputs numerically;
not necessarily by optimum configuration. The user may wish to make some educated re-assignment of outputs.
During device configuration, some output assignment was discussed since it impacted the part's configuration
relating to loop filter design, such as:
In this example, OSCout1 can be used to provide the power on reset (POR) start-up clock to the FPGA at
122.88 MHz since the VCXO frequency is the required output frequency.
Since PLL1 outputs have best in-band noise, OSCout0 is used to provide LVCMOS output to the PLL
reference for the LO. LVCMOS (Norm/Inv) is used instead of LVCMOS (Norm/Norm) to reduce crosstalk. It is
also possible to use CLKout6/7 or CLKout8/9 for a PLL reference being driven from the VCXO. The noise
floor will be higher, but close-in noise is typically of more concern since noise above the loop bandwidth of the
LO will be dominated by the VCO of the LO. See Figure 38.
Since CLKout6/7 and CLKout8/9 have a mux allowing them to be driven by the VCXO and due there is a chance
for some 122.88 MHz crosstalk from the VCXO. The 122.88 MHz SERDES clock will be placed on CLKout6
since it will not be sensitive to crosstalk as it is operating at the same frequency.
The two 245.76 MHz clocks and four 983.04 MHz clocks for the converters need to be discussed. There is some
flexibility in assignment. For example CLKout0/1 could operate at 245.76 MHz for the ADCs and then CLKout2/3
and CLKout4/5 could operate at 983.04 MHz for the DAC. It is also possible to consider CLKout2/3 for the ADC
and position CLKout0/1 and CLKout10/11 for the DAC. The ADCs clock was placed as far as possible from other
clock which could result in sub-harmonic spurs since the ADC clock is often the most sensitive.
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Typical Application (continued)
9.2.2.5 Other Device Specific Configuration
9.2.2.5.1 Digital Lock Detect
Digital lock time for PLL1 will ultimately depend upon the programming of the PLL1_DLD_CNT register as
discussed in Digital Lock Detect Frequency Accuracy. Since the PLL1 phase detector frequency in this example
is 3.84 MHz, the lock time will = 1 / (PLL1_DLD_CNT * 3.84 MHz)
Digital lock time for PLL1 if PLL1_DLD_CNT = 10000 is just over 2.6 ms. When using holdover, it is very
important to program the PLL1_DLD_CNT to a value large enough to prevent false digital lock detect signals.
If PLL1_DLD_CNT is too small, when the device exits holdover and is re-locking, the DLD will go high while the
phase of the reference and feedback are within the specified window size because the programmed
PLL1_DLD_CNT will be satisfied. However, if the loop has not yet settled to without the window size, when the
phases of the reference and feedback once again exceed the window size, the DLD will return low. Provided that
DISABLE_DLD1_DET = 0, the device once again enter holdover. Assuming that the reference clock is valid
because holdover was just exited, the exit criteria will again be met, holdover will exit, and PLL1 will start locking.
Unfortunately, the same sequence of events will repeat resulting in oscillation out-of and back-into holdover.
Setting the PLL1_DLD_CNT to an appropriately large value prevents chattering of the PLL1 DLD signal and
stable holdover operation can be achieved.
Refer to Holdover Mode - Automatic Exit of Holdover for more detail on calculating exit times and how the
PLL1_DLD_CNT and PLL1_WND_SIZE work together.
9.2.2.5.2 Holdover
For this example, when the recovered clock is lost, the goal is to set the VCXO to Vcc/2 until the recovered clock
returns. Holdover Mode contains detailed information on how to program holdover.
To achieve the above goal, fixed holdover will be used. Program:
HOLDOVER_MODE = 2 (Holdover enabled)
EN_TRACK = 0 (Tracking disabled)
EN_MAN_DAC = 1 (Use manual DAC for holdover voltage value)
MAN_DAC = 512 (Approximately Vcc/2)
DISABLE_DLD1_DET = 0 (Use PLL1 DLD = Low to start holdover)
9.2.2.6 Device Programming
The CodeLoader software is used to program the LMK04906 evaluation board using the LMK04906 profile. It
also allows the exporting of a register map which can be used to program the device to the user’s desired
configuration.
Once a configuration of dividers has been achieved using the Clock Design Tool to meet the requested
input/output frequencies with the desired performance, the CodeLoader software is manually updated with this
information to meet the required application. At this time no automatic import exists.
Frequency Offset (Hz)
Phase Noise (dBc/Hz)
-170
-165
-160
-155
-150
-145
-140
-135
-130
1k 10k 100k 1M 10M
D001
VCO CLKoutX
VCXO CLKout6/7/8/9
VCXO OSCout0/1
VCXO Direct
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Typical Application (continued)
9.2.3 Application Curve
Figure 38. LVPECL Phase Noise, 122.88 MHz
Illustration of Different Performance Depending on Signal Path.
9.3 System Examples
9.3.1 System Level Diagram
Figure 39 and Figure 40 show an LMK04906 family device with external circuitry for clocking and for power
supply to serve as a guideline for good practices when designing with the LMK04906 family. See Pin Connection
Recommendations for more details on the pin connections and bypassing recommendations. Also refer to the
evaluation board. PCB design will also play a role in device performance.
CPout1
LEuWire
CLKuWire
DATAuWire
To Host
processor
LDObyp1
LDObyp2
10 PF0.1 PF
LMK04906
OSCin
OSCin*
100:
0.1 PF
0.1 PF
PLL1 Loop Filter
Rterm
0.1 PF
CLKin2
CLKin2*
50:0.1 PF
0.1 PFCLKin0
CLKin0*
Recovered
Reference
Clocks
0.1 PF
CPout2
PLL2 External
Loop Filter
CLKout2*,3*
CLKout2, 3
0.1 PF
240:
2x LVPECL
output clocks
to ADC
0.1 PF
240:
LVDS clock to
FPGAs or
microcontroller
OSCout0*
OSCout0
0.1 PF
240:
LVPECL
OSCout clocks
to PLL
references
0.1 PF
240:
CLKout4 active at startup
OSCout0 on at startup
CLKout0*, 1*
CLKout0, 1
0.1 PF
240:
2x LVPECL
output clocks
to DAC
0.1 PF
240:
CLKout5*
CLKout5 LVDS Low
Frequency
System
Synchronization
Clock
CLKout4*
CLKout4
Up to 7 total differential clocks
SYNC
Status_HOLDOVER
Status_LD
Status_CLKin1
Status_CLKin0
100:
0.1 PF
0.1 PFCLKin1
CLKin1*
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System Examples (continued)
Figure 39. Example Application System Schematic Except for Power
Figure 39 shows the primary reference clock input is at CLKin0/0*. A secondary reference clock is driving
CLKin1/1*. Both clocks are depicted as AC coupled differential drivers. The VCXO attached to the OSCin/OSCin*
port is configured as an AC coupled single-ended driver. Any of the input ports (CLKin0/0*, CLKin1/1*,
CLKin2/2*or OSCin/OSCin*) may be configured as either differential or single-ended. These options are
discussed later in the data sheet.
See Loop Filter for more information on PLL1 and PLL2 loop filters.
LMK04906
FB = Ferrite bead
Vcc13 CLKout0
Vcc12 CLKout5
Vcc11 CLKout4
Vcc10 CLKout3
Vcc9 PLL2 N Divider
Vcc7 OSCin/OSCout0/
PLL2 Circuitry
Vcc6 PLL1 CP
Vcc4 Digital
Vcc3 CLKout2
Vcc2 CLKout1
Vcc1 VCO LDO
Vcc8 PLL2 CP
FB
FB
FB
FB
FB
Vcc5 CLKin/OSCout1
PLL Supply Plane
Clock Supply Plane
LDO
LP3878-ADJ
10 PF, 1 PF, 0.1 PF
10 PF, 1 PF, 0.1 PF 1 PF, 0.1 PF, 10 nF
0.1 PF
0.1 PF
0.1 PF
0.1 PF
FB
FB
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System Examples (continued)
The clock outputs are all AC coupled with 0.1 µF capacitors. Some clock outputs are depicted as LVPECL with
240 Ωemitter resistors and some clock outputs as LVDS. However, the output format of the clock outputs will
vary by user programming, so the user should use the appropriate source termination for each clock output.
Later sections of this data sheet illustrate alternative methods for AC coupling, DC coupling and terminating the
clock outputs.
PCB design will influence crosstalk performance. Tightly coupled clock traces will have less crosstalk than
loosely coupled clock traces. Also proximity to other clocks traces will influence crosstalk.
Figure 40. Example Application Power System Schematic
Figure 40 shows an example decouping and bypassing scheme for the LMK04906. Components drawn in dotted
lines are optional. Two power planes are used in this design, one for the clock outputs and one for other PLL
circuits.
PCB design will influence impedance to the supply. Vias and traces will increase the impedance to the power
supply. Ensure good direct return current paths.
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9.4 Do's and Don'ts
9.4.1 LVCMOS Complementary vs. Non-Complementary Operation
It is recommended to use a complementary LVCMOS output format such as LVCMOS (Norm/Inv) to reduce
switching noise and crosstalk when using LVCMOS.
If only a single LVCMOS output is required, the complementary LVCMOS output format can still be used by
leaving the unused LVCMOS output floating.
A non-complimentary format such as LVCMOS (Norm/Norm) is not recommended as increased switching
noise is present.
9.4.2 LVPECL Outputs
When using an LVPECL output it is not recommended to place a capacitor to ground on the output as might be
done when using a capacitor input LC lowpass filter. The capacitor will appear as a short to the LVPECL output
drivers which are able to supply large amounts of switching current. The effect of the LVPECL sourcing large
switching currents can result in:
1. Large switching currents through the Vcc pin of the LVPECL power supply resulting in more Vcc noise and
possible Vcc spikes.
2. Large switching currents injected into the ground plane through the capacitor which could couple onto other
Vcc pins with bypass capacitors to ground resulting in more Vcc noise and possible Vcc spikes.
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10 Power Supply Recommendations
10.1 Pin Connection Recommendations
10.1.1 Vcc Pins and Decoupling
All Vcc pins must always be connected.
Integrated capacitance on the LMK04906 makes external high frequency decoupling capacitors (1 nF)
unnecessary. The internal capacitance is more effective at filtering high frequency noise than off device bypass
capacitance because there is no bond wire inductance between the LMK04906 circuit and the bypass capacitor.
10.1.1.1 Vcc2, Vcc3, Vcc10, Vcc11, Vcc12, Vcc13 (CLKout Vccs)
Each of these pins has an internal 200 pF of capacitance.
Ferrite beads may be used to reduce crosstalk between different clock output frequencies on the same
LMK04906 device. Ferrite beads placed between the power supply and a clock Vcc pin will reduce noise
between the Vcc pin and the power supply. When several output clocks share the same frequency a single ferrite
bead can be used between the power supply and each same frequency CLKout Vcc pin.
When using ferrite beads on CLKout Vcc pins, care must be taken to ensure the power supply can source the
needed switching current.
In most cases a ferrite bead may be placed and the internal capacitance is sufficient.
If a ferrite bead is used with a low frequency output (typically 10 MHz) and a high current switching clock
output format such as non-complementary LVCMOS or high swing LVPECL is used, then...
the ferrite bead can be removed to the lower impedance to the main power supply and bypass capacitors,
or
localized capacitance can be placed between the ferrite bead and Vcc pin to support the switching current.
Note that decoupling capacitors used between the ferrite bead and a CLKout Vcc pin can permit high
frequency switching noise to couple through the capacitors into the ground plane and onto other
CLKout Vcc pins with decoupling capacitors. This can degrade crosstalk performance.
10.1.1.2 Vcc1 (VCO), Vcc4 (Digital), and Vcc9 (PLL2)
Each of these pins has internal bypass capacitance.
Ferrite beads should not be used between these pins and the power supply/large bypass capacitors because
these Vcc pins don’t produce much noise or a ferrite bead can cause phase noise disturbances and resonances.
The typical application diagram in Figure 40 shows all these Vccs connected to together to Vcc without a ferrite
bead.
10.1.1.3 Vcc6 (PLL1 Charge Pump) and Vcc8 (PLL2 Charge Pump)
Each of these pins has an internal bypass capacitor.
Use of a ferrite bead between the power supply/large bypass capacitors and PLL1 is optional. PLL1 charge
pump can be connected directly to Vcc along with Vcc1, Vcc4, and Vcc9. Depending on the application, a 0.1 uF
capacitor may be placed close to PLL1 charge pump Vcc pin.
A ferrite bead should be placed between the power supply/large bypass capacitors and Vcc8. Most applications
have high PLL2 phase detector frequencies and (> 50 MHz) such that the internal bypassing is sufficient and a
ferrite bead can be used to isolate this switching noise from other circuits. For lower phase detector frequencies
a ferrite bead is optional and depending on application a 0.1 uF capacitor may be added on Vcc8.
10.1.1.4 Vcc5 (CLKin), Vcc7 (OSCin & OSCout0)
Each of these pins has an internal 100 pF of capacitance. No ferrite bead should be placed between the power
supply/large bypass capacitors and Vcc5 or Vcc7.
These pins are unique since they supply an output clock and other circuitry.
Vcc5 supplies CLKin.
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Pin Connection Recommendations (continued)
Vcc7 supplies OSCin, OSCout0, and PLL2 circuitry.
10.1.2 Unused Clock Outputs
Leave unused clock outputs floating and powered down.
10.1.3 Unused Clock Inputs
Unused clock inputs can be left floating.
10.1.4 LDO Bypass
The LDObyp1 and LDObyp2 pins should be connected to GND through external capacitors, as shown in the
diagram.
10.2 Current Consumption and Power Dissipation Calculations
From Table 118 the current consumption can be calculated for any configuration.
For example, the current for the entire device with 1 LVDS (CLKout0) and 1 LVPECL 1.6 Vpp /w 240 ohm
emitter resistors (CLKout1) output active with a clock output divide = 1, and no other features enabled can be
calculated by adding up the following blocks: core current, clock buffer, one LVDS output buffer current, and one
LVPECL output buffer current. There will also be one LVPECL output drawing emitter current, which means
some of the power from the current draw of the device is dissipated in the external emitter resistors which
doesn't add to the power dissipation budget for the device but is important for LDO ICC calculations.
For total current consumption of the device, add up the significant functional blocks. In this example, 228.1 mA =
140 mA (core current)
17.3 mA (base clock distribution)
25.5 mA (CLKout0 & 1 divider)
14.3 mA (LVDS buffer)
31 mA (LVPECL 1.6 Vpp buffer /w 240 ohm emitter resistors)
Once total current consumption has been calculated, power dissipated by the device can be calculated. The
power dissipation of the device is equation to the total current entering the device multiplied by the voltage at the
device minus the power dissipated in any emitter resistors connected to any of the LVPECL outputs. If no emitter
resistors are connected to the LVPECL outputs, this power will be 0 watts. Continuing the above example which
has 228.1 mA total Icc and one output with 240 ohm emitter resitors. Total IC power = 717.7 mW = 3.3 V * 228.1
mA - 35 mW.
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Current Consumption and Power Dissipation Calculations (continued)
(1) Power is dissipated externally in LVPECL emitter resistors. The externally dissipated power is calculated as twice the DC voltage level
of one LVPECL clock output pin squared over the emitter resistance. That is to say power dissipated in emitter resistors = 2 * Vem2/
Rem.
Table 118. Typical Current Consumption for Selected Functional Blocks
(TA= 25 °C, VCC = 3.3 V)
BLOCK CONDITION TYPICAL
ICC
(mA)
POWER
DISSIPATE
D IN
DEVICE
(mW)
POWER
DISSIPATE
D
EXTERNAL
LY(1)
(mW)
CORE AND FUNCTIONAL BLOCKS
Core
MODE = 0: Dual Loop, Internal VCO PLL1 and PLL2 locked 140 462
MODE = 2: Dual Loop, Internal VCO,
0-Delay PLL1 and PLL2 locked; Includes
EN_FEEDBACK_MUX = 1 155 512
MODE = 3: Dual Loop, External VCO PLL1 and PLL2 locked 127 419
MODE = 5: Dual Loop, External VCO,
0-Delay PLL1 and PLL2 locked; Includes
EN_FEEDBACK_MUX = 1 142 469
MODE = 6: Single Loop (PLL2),
Internal VCO PLL2 locked 116 383
MODE = 11: Single Loop (PLL2),
External VCO PLL2 locked 103 340
MODE = 16: Clock Distribution PD_OSCin = 0 42 139
PD_OSCin = 1 34.5 114
EN_TRACK Tracking is enabled (EN_TRACK = 1) 2 6.6
Base Clock
Distribution At least 1 CLKoutX_PD = 0 17.3 57.1
CLKout Outputs Each CLKout Output 2.8 9.2
Clock Divider/
Digital Delay When a clock output is enabled, this contributes the divider/delay block 25.5 84.1
Divider / digital delay in extended mode 29.6 97.7
VCO Divider VCO Divider current 7.7 25.4
HOLDOVER
mode When in holdover mode 2.2 7.2
Feedback Mux Feedback mux must be enabled for 0-delay modes and digital delay mode
(SYNC_QUAL = 1) 4.9 16.1
SYNC Asserted While SYNC is asserted, this extra current is drawn 1.7 5.6
EN_SYNC = 1 Required for SYNC functionality. May be turned off once SYNC is complete
to save power. 6 19.8
SYNC_QUAL = 1 Delay enabled, delay > 7 (CLKout_MUX = 2, 3) 8.7 28.7
Crystal Mode Enabling the Crystal Oscillator
XTAL_LVL = 0 1.8 5.9
XTAL_LVL = 1 2.7 9
XTAL_LVL = 2 3.6 12
XTAL_LVL = 3 4.5 15
OSCin Doubler EN_PLL2_REF_2X = 1 2.8 9.2
Analog Delay Analog Delay Value
CLKoutX_ANLG_DLY = 0 to 3 3.4 11.2
CLKoutX_ANLG_DLY = 4 to 7 3.8 12.5
CLKoutX_ANLG_DLY = 8 to 11 4.2 13.9
CLKoutX_ANLG_DLY = 12 to 15 4.7 15.5
CLKoutX_ANLG_DLY = 16 to 23 5.2 17.2
Clock Output Has Analog Delay Selected. Example:
CLKout0_ADLY_SEL = 1 2.8 9.2
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Current Consumption and Power Dissipation Calculations (continued)
Table 118. Typical Current Consumption for Selected Functional Blocks
(TA= 25 °C, VCC = 3.3 V) (continued)
BLOCK CONDITION TYPICAL
ICC
(mA)
POWER
DISSIPATE
D IN
DEVICE
(mW)
POWER
DISSIPATE
D
EXTERNAL
LY(1)
(mW)
CLOCK OUTPUT BUFFERS
LVDS 100-Ωdifferential termination 14.3 47.2
LVPECL
LVPECL 2.0 Vpp, AC coupled using 240-Ωemitter resistors 32 70.6 35
LVPECL 1.6 Vpp, AC coupled using 240-Ωemitter resistors 31 67.3 35
LVPECL 1.6 Vpp, AC coupled using 120-Ωemitter resistors 46 91.8 60
LVPECL 1.2 Vpp, AC coupled using 240-Ωemitter resistors 30 59 40
LVPECL 0.7 Vpp, AC coupled using 240-Ωemitter resistors 29 55.7 40
LVCMOS
LVCMOS Pair (CLKoutX_TYPE = 6
to 9)
CL= 5 pF
3 MHz 24 79.2
30 MHz 26.5 87.5
150 MHz 36.5 120.5
LVCMOS Single (CLKoutX_TYPE =
10 to 13)
CL= 5 pF
3 MHz 15 49.5
30 MHz 16 52.8
150 MHz 21.5 71
11 Layout
11.1 Layout Guidelines
Power consumption of the LMK04906 can be high enough to require attention to thermal management. For
reliability and performance reasons the die temperature should be limited to a maximum of 125°C. That is, as an
estimate, TA(ambient temperature) plus device power consumption times θJA should not exceed 125°C.
The package of the device has an exposed pad that provides the primary heat removal path as well as excellent
electrical grounding to a printed circuit board. To maximize the removal of heat from the package a thermal land
pattern including multiple vias to a ground plane must be incorporated on the PCB within the footprint of the
package. The exposed pad must be soldered down to ensure adequate heat conduction out of the package.
A recommended land and via pattern is shown in Figure 41. More information on soldering WQFN packages can
be obtained: http://www.ti.com/packaging.
To minimize junction temperature it is recommended that a simple heat sink be built into the PCB (if the ground
plane layer is not exposed). This is done by including a copper area of about 2 square inches on the opposite
side of the PCB from the device. This copper area may be plated or solder coated to prevent corrosion but
should not have conformal coating (if possible), which could provide thermal insulation. The vias shown in
Figure 41 should connect these top and bottom copper layers and to the ground layer. These vias act as “heat
pipes” to carry the thermal energy away from the device side of the board to where it can be more effectively
dissipated.
0.2 mm
1.46 mm
7.2 mm
1.15 mm
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Layout Guidelines (continued)
Figure 41. Recommended Land and Via Pattern
CLKin and OSCin path ± if differential input (preferred) route trace
tightly coupled like clock outputs. If single ended, have at least 3 trace
width (of CLKin/OSCin trace) separation from other RF traces.
Example shown is hybrid for both differential and single ended ± not
tightly couple to compromise for both configurations. RF Terminations
should be placed as close to IC as possible. When using CLKin1 for
high frequency input for external VCO or distribution, a 3 dB pi pad is
suggested for termination.
)RU&/.RXW9FF¶VSODFHIHUULWHEHDGVRQWRSOD\HUFORVHWRSLQVWRFKRNH
high frequency noise from via.
Charge pump output ± shorter traces are better.
Place all resistors and caps closer to IC except for
a single capacitor next to VCXO. In a 2nd order
filter place C1 close to VCXO Vtune pin. In a 3rd
and 4th order filter place C3 or C4 respectively
close to VCXO.
Clock outputs ± differential signals, should be
routed tightly coupled to minimize PCB crosstalk.
Trace impedance and terminations should be
designed according to output type being used (i.e.
LVDS, LVPECL...)
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11.2 Layout Example
Figure 42. LMK04906 Layout Example
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12 Device and Documentation Support
12.1 Device Support
Clock Design Tool
Clock Architect
Packaging Information
Clock and Timing
12.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
12.3 Community Resource
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
12.4 Trademarks
PLLatinum, E2E are trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.
12.5 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
12.6 Glossary
SLYZ022 TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
PACKAGE OPTION ADDENDUM
www.ti.com 10-Dec-2020
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead finish/
Ball material
(6)
MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
LMK04906BISQ/NOPB ACTIVE WQFN NKD 64 1000 RoHS & Green SN Level-3-260C-168 HR -40 to 85 K04906BISQ
LMK04906BISQE/NOPB ACTIVE WQFN NKD 64 250 RoHS & Green SN Level-3-260C-168 HR -40 to 85 K04906BISQ
LMK04906BISQX/NOPB ACTIVE WQFN NKD 64 2000 RoHS & Green SN Level-3-260C-168 HR -40 to 85 K04906BISQ
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.
(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6) Lead finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material values may wrap to two
lines if the finish value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
PACKAGE OPTION ADDENDUM
www.ti.com 10-Dec-2020
Addendum-Page 2
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
LMK04906BISQ/NOPB WQFN NKD 64 1000 330.0 16.4 9.3 9.3 1.3 12.0 16.0 Q1
LMK04906BISQE/NOPB WQFN NKD 64 250 178.0 16.4 9.3 9.3 1.3 12.0 16.0 Q1
LMK04906BISQX/NOPB WQFN NKD 64 2000 330.0 16.4 9.3 9.3 1.3 12.0 16.0 Q1
PACKAGE MATERIALS INFORMATION
www.ti.com 13-Aug-2017
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
LMK04906BISQ/NOPB WQFN NKD 64 1000 367.0 367.0 38.0
LMK04906BISQE/NOPB WQFN NKD 64 250 210.0 185.0 35.0
LMK04906BISQX/NOPB WQFN NKD 64 2000 367.0 367.0 38.0
PACKAGE MATERIALS INFORMATION
www.ti.com 13-Aug-2017
Pack Materials-Page 2
www.ti.com
PACKAGE OUTLINE
C
64X 0.3
0.2
7.2 0.1
60X 0.5
64X 0.5
0.3
0.8 MAX
4X
7.5
A
9.1
8.9
B9.1
8.9
0.3
0.2
0.5
0.3
(0.1)
TYP
4214996/A 08/2013
WQFN - 0.8 mm max heightNKD0064A
WQFN
PIN 1 INDEX AREA
SEATING PLANE
1
16 33
48
17 32
64 49
(OPTIONAL)
PIN 1 ID
SEE TERMINAL
DETAIL
NOTES:
1. All linear dimensions are in millimeters. Dimensions in parenthesis are for reference only. Dimensioning and tolerancing
per ASME Y14.5M.
2. This drawing is subject to change without notice.
3. The package thermal pad must be soldered to the printed circuit board for thermal and mechanical performance.
0.1 C A B
0.05 C
SCALE 1.600
DETAIL
OPTIONAL TERMINAL
TYPICAL
www.ti.com
EXAMPLE BOARD LAYOUT
( 7.2)
0.07 MIN
ALL AROUND
0.07 MAX
ALL AROUND
64X (0.6)
64X (0.25)
(8.8)
(8.8)
60X (0.5)
() VIA
TYP
0.2
(1.36)
TYP
8X (1.31)
(1.36) TYP 8X (1.31)
4214996/A 08/2013
WQFN - 0.8 mm max heightNKD0064A
WQFN
SYMM
SEE DETAILS
1
16
17 32
33
48
49
64
SYMM
LAND PATTERN EXAMPLE
SCALE:8X
NOTES: (continued)
4. This package is designed to be soldered to a thermal pad on the board. For more information, refer to QFN/SON PCB application note
in literature No. SLUA271 (www.ti.com/lit/slua271).
SOLDER MASK
OPENING
METAL
SOLDER MASK
DEFINED
METAL
SOLDER MASK
OPENING
SOLDER MASK DETAILS
NON SOLDER MASK
DEFINED
(PREFERRED)
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EXAMPLE STENCIL DESIGN
(8.8)
64X (0.6)
64X (0.25)
25X (1.16)
(8.8)
60X (0.5)
(1.36) TYP
(1.36)
TYP
4214996/A 08/2013
WQFN - 0.8 mm max heightNKD0064A
WQFN
NOTES: (continued)
5. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate
design recommendations.
SYMM
METAL
TYP
SOLDERPASTE EXAMPLE
BASED ON 0.125mm THICK STENCIL
EXPOSED PAD
65% PRINTED SOLDER COVERAGE BY AREA
SCALE:10X
1
16
17 32
33
48
49
64
SYMM
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