General Description
The DS1090 is a low-cost, dithered oscillator intended
to be used as an external clock for switched-mode
power supplies and other low-frequency applications. The
dithering or sweeping function reduces peak-radiated
emissions from the power supply at its fundamental
frequency, as well as harmonic frequencies. The device
consists of a resistor-programmed master oscillator, fac-
tory-programmed clock prescaler, and a pin-programmed
dither circuit. These features allow the DS1090 to be used
in applications where a spread-spectrum clock is desired
to reduce radiated emissions. A combination of factory-set
prescalers and external resistor allows for output frequencies
ranging from 125kHz to 8MHz. Both dither frequency and
dither percentage are set using control pins.
Applications
●Switched-Mode Power Supplies
●Servers
●Printers
●Embedded Microcontrollers
●Industrial Controls
Features
●Low-Cost, Spread-Spectrum EconOscillator™
●Simple User Programming
●
Output Frequency Programmable from 125kHz to 8MHz
● Dither Percentage Programmable from 0% to 8%
● Dither Rate Programmable (fMOSC/512, 1024, 2048,
or 4096)
● 3.0V to 5.5V Single-Supply Operation
● CMOS/TTL-Compatible Output
● Operating Temperature Range: -40°C to +85°C
Add “T” for Tape & Reel orders.
EconOscillator is a trademark of Maxim Integrated Products, Inc.
PART
OUTPUT
FREQUENCY
RANGE
PRESCALER PIN-
PACKAGE
DS1090U-1+ 4MHz to 8MHz 1 8 µSOP
DS1090U-2+ 2MHz to 4MHz 2 8 µSOP
DS1090U-4+ 1MHz to 2MHz 4 8 µSOP
DS1090U-8+ 500kHz to
1MHz 8 8 µSOP
DS1090U-16+ 250kHz to
500kHz 16 8 µSOP
DS1090U-32+ 125kHz to
250kHz 32 8 µSOP
J1
J0GND
1
2
8
7
JC1
JC0RSET
VCC
OUT
µSOP
TOP VIEW
3
4
6
5
DS1090
DS1090
VOUT
VIN
DC-DC
STEP-DOWN
CONVERTER
OUT
GND
VCC
VCC
RSET
JC0
JC1
J0
J1
45kΩ
TO 91kΩ
DS1090 Low-Frequency, Spread-Spectrum EconOscillator
19-7500; Rev 3; 9/16
Ordering Information
Pin Conguration
Typical Operating Circuit
Voltage Range on VCC Relative to Ground .........-0.5V to +6.0V
Voltage Range on Input Pins
Relative to Ground............................... -0.5V to (VCC + 0.5V),
not to exceed 6.0V
Operating Temperature Range ........................... -40°C to +85°C
Storage Temperature Range ............................ -55°C to +125°C
Soldering Temperature ......................................See IPC/JEDEC
J-STD-020A Specification
(TA = -40°C to +85°C)
(VCC = +3.0V to +5.5V, TA = -40°C to +85°C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage VCC (Note 1) 3.0 5.5 V
Input Logic 1 (J0, J1, JC0, JC1) VIH
0.7 x
VCC
VCC +
0.3 V
Input Logic 0 (J0, J1, JC0, JC1) VIL -0.3 +0.3 x
VCC
V
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Current ICC
CL = 15pF, VCC = 3.3V, RSET = 40kΩ 1.4 mA
CL = 15pF, VCC = 5.5V, RSET = 40kΩ 1.7 3
High-Level Output Voltage (OUT) VOH
IOH = -4mA 2.4 V
VCC = min
Low-Level Output Voltage (OUT) VOL IOL = 4mA 0.4 V
High-Level Input Current
(J0, J1, JC0, JC1) IIH VIH = VCC +1.0 µA
Low-Level Input Current
(J0, J1, JC0, JC1) IIL VIL = 0V -1.0 µA
Resistor Current IRES VCC = max 150 µA
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DS1090 Low-Frequency, Spread-Spectrum EconOscillator
Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
DC Electrical Characteristics
Recommended DC Operating Conditions
Note 1: All voltages referenced to ground.
Note 2: This is the change observed in output frequency due to changes in temperature or voltage.
Note 3: See the Typical Operating Characteristics section.
Note 4: Parameter is guaranteed by design and is not production tested.
Note 5: This is a percentage of the output period. Parameter is characterized but not production tested. This can be varied from 0%
to 8%.
Note 6: This indicates the time between power-up and the outputs becoming active. An on-chip delay is intentionally introduced to
allow the oscillator to stabilize. tSTAB is equivalent to ~500 clock cycles and is dependent upon the programmed
output frequency.
Note 7: Output voltage swings can be impaired at high frequencies combined with high output loading.
(VCC = +3.0V to +5.5V, TA = -40°C to +85°C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Internal Master Oscillator
Frequency fMOSC 4.0 8.0 MHz
Output Frequency Tolerance ∆fOUT
VCC = 3.3V,
TA = +25°C -3.0 +3.0 %
Voltage Frequency Variation ∆fOUT
TA = +25°C, RSET = 60kΩ,
VCC = 3.0V to 3.6V (Notes 2, 3) -0.5 +0.5
%
TA = +25°C, RSET = 60kΩ,
VCC = 4.5V to 5.5V (Notes 2, 3) -1.25 +1.25
Temperature Frequency Variation ∆fOUT
VCC = 3.3V
(Notes 2, 3, 4) -2.0 +2.0 %
Peak-to-Peak Dither (3σ)
(Note 5)
J0 = GND, J1 = GND 0
%
J0 = VCC, J1 = GND 2
J0 = GND, J1 = VCC 4
J0 = VCC, J1 = VCC 8
Power-Up Time tPOR +
tSTAB
(Note 6) 0.1 0.5 ms
Load Capacitance CL(Note 7) 30 pF
Output Duty Cycle 4MHz to 8MHz, TA = +25°C (Note 3) 45 55 %
<4MHz (Note 4) 50
Output Rise/Fall Time tR, tFCL = 15pF 20 ns
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DS1090 Low-Frequency, Spread-Spectrum EconOscillator
AC Electrical Characteristics
(VCC = +3.3V, TA = +25°C, unless otherwise noted.)
DS1090 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
5.04.54.03.5
0.95
1.20
1.45
1.70
0.70
3.0 5.5
NO LOAD, TA = +25°C
40kΩ
60kΩ
80kΩ
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SUPPLY CURRENT
vs. TEMPERATURE
DS1090 toc02
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
603510-15
0.70
0.90
1.10
1.30
1.50
0.50
-40 85
NO LOAD, VCC = 3.3V
40kΩ
60kΩ
80kΩ
SUPPLY CURRENT
vs. OUTPUT LOADING
DS1090 toc03
LOAD CAPACITANCE (pF)
SUPPLY CURRENT (mA)
353025201510
1
2
3
4
0
5 40
TA = +25°C, RSET = 40kΩ
4V
3V
5V
OUTPUT VOLTAGE HIGH
vs. OUTPUT CURRENT
DS1090 toc04
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
-1-2-3-4
2.8
2.9
3.0
3.1
2.7
-5 0
VCC = 3.0V
OUTPUT VOLTAGE LOW
vs. OUTPUT CURRENT
DS1090 toc05
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
4321
0.1
0.2
0.3
0.4
0
0 5
VCC = 3.0V
OUTPUT FREQUENCY
vs. SUPPLY VOLTAGE
DS1090 toc06
SUPPLY VOLTAGE (V)
FREQUENCY (MHz)
5.04.54.03.5
5
6
7
8
9
10
4
3.0 5.5
TA = +25°C
60kΩ
80kΩ
40kΩ
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DS1090 Low-Frequency, Spread-Spectrum EconOscillator
Typical Operating Characteristics
(VCC = +3.3V, TA = +25°C, unless otherwise noted.)
OUTPUT FREQUENCY
vs. TEMPERATURE
DS1090 toc07
TEMPERATURE (°C)
FREQUENCY (MHz)
603510-15
5
6
7
8
9
10
4
-40 85
VCC = 3.3V
60kΩ
80kΩ
40kΩ
DUTY CYCLE
vs. TEMPERATURE
DS1090 toc08
TEMPERATURE (°C)
DUTY CYCLE (%)
603510-15
49
50
51
52
48
-40 85
RSET = 40kΩ
VCC = 3.3V
VCC = 5V
DS1090U-1
RESISTOR CURRENT
vs. RESISTOR VALUE
DS1090 toc09
RSET (kΩ)
RESISTOR CURRENT (mA)
706050
10
12
14
16
18
8
40 80
VCC = 3.3V, TA = +25°C
FREQUENCY ERROR
vs. SUPPLY VOLTAGE (FROM 3.3V)
DS1090 toc10
SUPPLY VOLTAGE (V)
FREQUENCY ERROR (%)
5.04.54.03.5
-2.5
0
2.5
5.0
-5.0
3.0 5.5
T
A
= +25°C
40kΩ
60kΩ
80kΩ
FREQUENCY ERROR
vs. TEMPERATURE (FROM +25°C)
DS1090 toc11
TEMPERATURE (°C)
FREQUENCY ERROR (%)
603510-15
-1.0
0
1.0
2.0
-2.0
-40 85
VCC = 3.3V
40kΩ
60kΩ
80kΩ
POWER SPECTRUM vs. SPREAD
DS1090 toc12
FREQUENCY (MHz)
POWER (dBm)
5.35
-70
-60
-50
-40
-30
-20
-10
0
-80
4.80 5.90
VCC = 3.3V,
TA = +25°C,
JC0 = JC1 = 1
OFF
2%
4%
8%
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DS1090 Low-Frequency, Spread-Spectrum EconOscillator
Typical Operating Characteristics (continued)
PIN NAME FUNCTION
1 OUT Oscillator Output
2 RSET Frequency Control Resistor Input
3 VCC Positive-Supply Terminal
4 GND Ground
5 J0 Dither Amplitude (Percentage) Inputs
(see Table 2)
6 J1
7 JC0 Dither Rate Divisor Inputs (see Table 1)
8 JC1
DS1090
∑
GND
MASTER
OSCILLATOR
(VCO)
4MHz–8MHz
FACTORY
PROGRAMMED
PRESCALER
( 1, 2, 4, 8, 16, OR 32)
TRIANGLE
GENERATOR
VCC
VCC
RSET VOLTAGE-
BIAS CIRCUIT
OUT
fMOSC fOSC
fMOD
fOUT
J0
J1
JC0
JC1
BUFFER
+
+
DITHER
AMPLITUDE
(0, 2, 4, OR 8%)
DITHER RATE
( 4, 8, 16, OR 32)
+
-
( 128)
DITHER GENERATOR
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DS1090 Low-Frequency, Spread-Spectrum EconOscillator
Block Diagram
Pin Description
Detailed Description
The DS1090 is a center-dithered, spread-spectrum silicon
oscillator for use as an external clock in reduced-EMI
applications. With a combination of factory-programmed
prescalers and a user-selected external resistor, output
frequencies from 125kHz to 8MHz can be achieved. The
output center frequency can be dithered by selecting the
desired dither rate and amplitude with discrete inputs J0,
J1, JC0, and JC1.
The DS1090 contains four basic circuit blocks: master
oscillator, factory-programmed prescaler, dither generator,
and the voltage-bias circuit that provides the feedback
path to the master oscillator for frequency control and
dithering functions.
Master Oscillator
The master oscillator is programmable in the application
by the use of an external resistor (RSET) tied to ground
(GND). Resistor values of 45kΩ to 91kΩ vary the
square-wave output frequency of the voltage-controlled
master oscillator (fMOSC) from 8MHz down to 4MHz
(see Figure 1).
The master oscillator (Hz) frequency can be stated as
MOSC
3.6461 E 11
fResistor
+
≅
Factory-Programmed Prescaler
The prescaler divides the frequency of the master oscillator
by 1, 2, 4, 8, 16, or 32 to generate the square-wave output
clock (fOSC). This divisor is factory-set and is an ordering
option.
Dither Generator
Spread-spectrum functionality is achieved by a user-
configurable divider (determines dither rate), a triangle
generator, and a user-configurable dither amplitude circuit
(see Block Diagram).
The input to the triangle-wave generator is derived
from the internal master oscillator and is fed through a
user-configurable divider. The settings of control pins JC0
and JC1 determine this dither rate divisor setting (see
Table 1), dividing the master clock by 4, 8, 16, or 32. The
clock signal is further divided by 128 in the triangle-wave
generator, which results in a triangle-wave signal of either
1/512th, 1/1024th, 1/2048th, or 1/4096th of the master
oscillator (fMOD), depending upon the user’s divisor set-
ting.
The dithering frequency can be also expressed as the
result of
where Divisor is 4, 8, 16, or 32.
MOSC
MOD
f
fDivisor 128
=
×
Figure 2. Center Frequency Dither Diagram
Figure 1. Master Oscillator Frequency
Table 1. Dither Rate Divisor Settings
JC1 JC0 DITHERING PERCENTAGE
(fMOSC/n)
DIVISOR
SETTING
0 0 fMOSC /512 4
0 1 fMOSC /1024 8
1 0 fMOSC /2048 16
1 1 fMOSC /4096 32
MASTER OSCILLATOR FREQUENCY vs.
EXTERNAL RESISTOR SELECTION
DS1090 fig01
RSET RESISTANCE (kΩ)
fMOSC (MHz)
90
80
7060
50
4
5
6
7
8
9
3
40
fMOSC
TIME
DITHER
AMOUNT
(2, 4, OR 8%)
IF DITHER AMOUNT = 0%
(- 1, 2, or 4% of fMOSC)
fMOD
1
(+ 1, 2, or 4% of fMOSC)
Programmed fMOSC
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DS1090 Low-Frequency, Spread-Spectrum EconOscillator
Dither Percentage Settings
Dither amplitude (measured in percent ± from the master
oscillator center frequency) is set using input pins J0 and
J1. This circuit uses a sense current from the master
oscillator bias circuit to adjust the amplitude of the tri-
angle-wave signal to a voltage level that modulates the
master oscillator to a percentage of its resistor-set center
frequency. This percentage is set in the end application to
be 0%, 2%, 4%, or 8% (see Table 2).
Application Information
Pin Connection
The DS1090 is intended to provide a fixed-frequency,
dithered clock to be used as a clock driver for DC-DC
converters and other applications requiring a low-
frequency EMI-reduced clock oscillator. All control pins
must be biased per Tables 1 and 2 for proper operation
for the individual application’s requirements. RSET must
be tied to ground (GND) by a customer-supplied resistor.
RSET Resistor Selection
The value of the resistor used to select the desired
frequency is calculated using the formula in the Master
Oscillator section (see also Figure 1). It is recommended
to use, at minimum, a 1%-tolerance, 1/16th-watt component
with a temperature coefficient that satisfies the overall
stability requirements desired of the end-equipment.
Place the external RSET resistor as close as possible to
minimize lead inductance.
Power-Supply Decoupling
To achieve best results, it is highly recommended that a
decoupling capacitor is used on the IC power-supply pins.
Typical values of decoupling capacitors are 0.01µF and
0.1µF. Use a high-quality, ceramic, surface-mount capaci-
tor, and mount it as close as possible to the VCC and GND
pins of the IC to minimize lead inductance.
Table 2. Dither Percentage Setting
J1 J0 DITHER PERCENT (%)
0 0 0
0 1 2
1 0 4
1 1 8
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DS1090 Low-Frequency, Spread-Spectrum EconOscillator
Chip Information
SUBSTRATE CONNECTED TO GROUND
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2016 Maxim Integrated Products, Inc.
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DS1090 Low-Frequency, Spread-Spectrum EconOscillator
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
1 2/07 — —
2 2/15 Remove automotive reference from data sheet 1
3 9/16 Corrected typo in Benets and Features section 1
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DS1090U-1+ DS1090U-1+T DS1090U-16+ DS1090U-16+T DS1090U-2+ DS1090U-2+T DS1090U-32+
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DS1090U-8/V+ DS1090U-8/V+T