MICRF112
300MHz to 450MHz, +10dBm, 1.8V to 3.6V,
ASK/FSK Transmitter with Shutdown
QwikRadio is a registered tradem ark of Micrel, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
Febr
uary 2013
M9999-020713
General Description
The MICRF112 is a high-performance, easy to use, true
“Data-In, RF-Out,” ASK/FSK, phase-locked loop (PLL)
based, transmitter IC for applications in the 300MHz to
450MHz frequency range. These applications include
remote keyless entry (RKE) and tire pressure monitoring
(TPMS). The device needs only a low-cost crystal to
precisel y set the des ired RF f requency, and a few exter nal
components for m atching t he power amplif ier output t o the
antenna.
The MICRF112 operates over the 1.8V to 3.6V operating
range and delivers +10dBm (CW) output power into a 50Ω
load, while consuming 11.5mA of supply current from a
3.0V power supply. In ASK mode, the device consumes
6.9mA of supply current at a data rate of 1kbps
(Manchester 50%). It features a low-power shutdown
mode in which the device typically consumes 50nA of
supply current. This makes it an ideal solution for battery
powered applications.
The MICRF112 is rated for the −40°C to +125°C
temperature range, and is available in 10-pin MSOP and
10-pin Ultra-Thin DFN packages. For automotive
applications, where AEC-Q100 qualification is required,
consider the MAQRF112. For ASK-only applications that
do not require shutdown, consider the MICRF113 in
SOT23-6.
Datasheets and support documentation can be found on
Micrel’s webs ite at : www.micrel.com.
Features
• 1.8V to 3.6V supply voltage range
• Up to +10dBm output power (CW)
• 6.9mA supply current at 1kbps ASK (50% Manchester)
• 11.5mA supply current at +10dBm (FSK/CW)
• 1µA shutdown supply current
• Data rates up to 50kbps ASK, 10kbps FSK
• Crystal or ceramic resonators sets RF frequency
• −40°C to +125°C temperature range
• 10-pin MSOP (3.0mm x 4.9mm)
• 10-pin Ultra-Thin DFN (2mm x 2mm x 0.4mm)
Applications
• Remote keyless entry systems (RKE)
• Remote control (STB, HVAC, and appliances)
• Garage door openers (GDO)
• Tire pressure monitor systems (TPMS)
• Outdoor weather stations
• Security/Alarm systems
• Lighting and fan remote controls
• Doorbells
• Irrigation control
Typical Application
Micrel, Inc.
MICRF112
Febr
uary 2013 2 M9999-020713
Ordering Information
Pin Configuration
10-Pin Ultra-Thin DFN (MU)
(2mm x 2mm x 0.4mm)
Top View
10-Pin MSOP (MM)
Top View
Note: The Pin1 marking symbol could be a circle, triangle, or other symbol.
Pin Description
Pin Number
Pin Name
Pin Function
1 ASK ASK Data input
2 XTLIN Reference oscillator input connection
3 XTLOUT Reference oscillator output connection
4 VSS Ground
5 XTAL_MOD Reference oscillation modulation port for FSK operation
6 FSK F SK Da t a input
7 EN Chip enable, active high
8 VSSPA PA ground
9 PAOUT PA output
10 VDD Positive power supply
Part Number
Top Mark
Temp. Range
Package
MICRF112YMM RF112YMM –40°C to +125°C 10-Pin MSOP
MICRF112YMU 12B –40°C to +125°C 10-Pin UTDFN
Micrel, Inc.
MICRF112
Febr
uary 2013 3 M9999-020713
Absolute Maximum Ratings(1)
Supply Voltage (VDD) ................................................. +4.3V
Voltage on PAOUT ...................................................... +7.2V
Voltage on I/O Pins ........................ VSS – 0.3 to VDD + 0.3
Lead Temperature (soldering, 10s) .......................... +300°C
Storage Temperature (TS) ......................... −65°C to +150°C
ESD Rating ................................................................. Note 3
Operating Ratings(2)
Suppl y Voltage (VDD) ...................................... 1.8V to 3.6V
Ambient Operating Temperature (TA) ........ -40°C to +125°C
Transmitter Frequency Range ............. 300MHz to 450MHz
Electrical Characteristics(4)
Specifications apply for VDD = 3.0V, TA = 25°C, FreqREFOSC = 13.560MHz, EN = VDD. 1Kbps data rate, 50% duty cy cl e. RL 50Ω load
(matched)
Parameter Condition Min. Typ. Max. Units
Power Supply
Standby Supply Current, Iq EN = VSS 0.05 1 µA
Mark Supply Current ION @ 315MHz, POUT = +10dBm 11.5 mA
@ 433.92MH z, POUT = +10dBm 11.6 mA
SPACE Supply Current, IOFF @ 315MHz 2.4 mA
@ 433.92MHz 2.7 mA
RF Output Section and Modulation Limits:
Output Power Level, POUT
FSK or ASK "Mark" @ 315MHz
(4)
10 dBm
@ 433.92MHz
(4)
10 dBm
Harmonics output for
315MHz @ 630MHz
(4)
2nd harm. −53 dBc
@ 945MHz
(4)
3rd harm. −53 dBc
Harmonics Output for
433.92MHz @ 867.84MHz(4) 2nd harm. −51 dBc
@ 1301.76MHz
(4)
3rd harm. −65 dBc
Extinction Ratio for ASK 80 dBc
FSK Modulation
Frequency Deviation Load capacitor = 10pF, crystal type = HC49/U 22 kHz
Data Rate 10 Kbps
ASK Modulation
Data Rate 50 Kbps
Occupied Bandwidth @ 315MHz
(5)
<700 kHz
@ 433.92MHz
(5)
<1000 kHz
VCO Section
315MHz Single Side Band
Phase Noise @ 100kHz from Carrier −76 dBc/Hz
@ 1000kHz from Carrier −79 dBc/Hz
433.92MH z Single Side Band
Phase Noise @ 100kHz from Carrier −72 dBc/Hz
@ 1000kHz from Carrier −81 dBc/Hz
Reference Oscillator Section
XTLIN, XTLOUT, XTLMOD Pin capacitance 2 pF
External Capacitance See Schematic C17 & C18 18 pF
Oscillator Start-Up Ti me
(6)
Crystal: HC49S 400 µs
Micrel, Inc.
MICRF112
Febr
uary 2013 4 M9999-020713
Parameter Condition Min. Typ. Max. Units
Digital/Control Section
Output Blanking STDBY transition from low to high 500 µs
Digital Input (EN, ASK, and
FSK) High (VIH) 0.8 × VDD V
Low (VIL) 0.2 × VDD V
Digital Input Leakage Current
(EN, ASK, and FSK Pins) High (VIH) 0.05 µA
Low (VIL) 0.05 µA
Undervoltage Lock Out
(UVLO) 1.6 V
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guarant eed to function outside its operat i ng ratings.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
4. Measured using the circ uit shown in the “Test Circuit” section.
5. RBW = 100kHz, OBW measured at −20dBc.
6. Dependent on crystal .
Micrel, Inc.
MICRF112
Febr
uary 2013 5 M9999-020713
Test Circuit
MICRF112 Test Circuit with 50Ω Output (MSOP)
Notes:
1. Values without parenthesis are for 433.92MHz and values in parenthesis are for 315MHz.
2. C9 = 100pF for external REF-OSC.
3. For FSK R1 = 0Ω, R2 = NP, R6 = 100k, and R5 = NP.
Micrel, Inc.
MICRF112
Febr
uary 2013 6 M9999-020713
50Ω Evaluation Board PCB Layout
Assembly Drawing
MICRF112 50Ω Evaluation Board (MSOP)
Top Layer
MICRF112 50Ω Evaluation Board (MSOP)
Bottom Layer
MICRF112 50Ω Evaluation Board (MSOP)
Micrel, Inc.
MICRF112
Febr
uary 2013 7 M9999-020713
Typical Characteris tics Using MICRF112, 50Ω Evaluation Board (MSOP)
315MHz OBW, ASK = 1kHz
315MHz OBW, ASK = 50kHz
CW Max Pow er @ 3V, 315MHz,
ASK = 1kHz(1)
RF Spectrum 2nd Harmonic;
Fundamental at 315MHz
RF Spectrum 3rd Harmonic;
Fundamental at 315MHz
315MHz, Power Level at Space,
VDD = 3.0V, ASK = 1kHz
Note:
1. 1.2dB cable loss.
Micrel, Inc.
MICRF112
Febr
uary 2013 8 M9999-020713
Typical Charact eri s tics Using MICRF112, 50Ω Evaluation Board (MSOP) (Continued)
315MHz, Zero Span, ASK = 1kHz
315MHz, Zero Span, ASK = 50kHz
315MHz, Phase Noise, ASK = 1kHz,
100kHz Offset, –75.59dBc/Hz
315MHz, Phase Noise, ASK = 1kHz,
1MHz Offset, –78.99dBc/Hz
315MHz, Phase Noise, ASK = CW,
100kHz Offset, –74.39dBc/Hz
315MHz, Phase Noise, ASK = CW,
1MHz Offset, –77.28dBc/Hz
Micrel, Inc.
MICRF112
Febr
uary 2013 9 M9999-020713
Typical Characteristics Using MICRF112, 50Ω Evaluation Board (MSOP) (Continued)
433.92MHz OBW, ASK = 1kHz
433.92MHz OBW, ASK = 50kHz
433.92MHz, CW Max Power @ 3V,
ASK = 1kHz(1)
RF Spectrum 2nd Harmonic;
Fundamental at 433.92 MH z
RF Spectrum 3rd Harmonic;
Fundamental at 433.92 MH z
433.92MHz, Power Level at Space,
VDD = 3.0V, ASK = 1kHz
Note:
1. 1.3dB cable loss.
Micrel, Inc.
MICRF112
Febr
uary 2013 10 M9999-020713
Typical Characteristics Using MICRF112, 50Ω Evaluation Board (MSOP) (Continued)
433.92MHz Zero Span, 1kHz
433.92ASK Zero Span at 50kHz
433.92MHz Phase Noise, ASK = CW,
100kHz Offset, –81.04dBc/Hz
433.92MHz Phase Noise, ASK = CW,
1MHz Offset, –78.76dBc/Hz
433.92MHz Phase Noise, ASK = 1kHz,
100kHz Offset, –71.73dBc/Hz
433.92MHz Phase Noise, ASK = 1kHz,
1MHz Offset, –81.04dBc/H
Micrel, Inc.
MICRF112
Febr
uary 2013 11 M9999-020713
Functional Diagram
Figure 1. Functional Block Diagram MICRF112 10 Pin ASK/FSK Version
Functional Description
Figure 1 shows a functional block diagram of the
MICRF112 transmitter. The MICRF112 can be best
described as a phase-locked transmitter. The system
can be partitioned into six functional blocks: crystal
oscillator, PLL×32, power amplifier, enable control,
undervoltage detect, and open-drain switch for FSK
operation.
Crystal Oscillator
The reference oscillator is a crystal-based Pierce
configuration. It is designed to accept crystals with
frequencies from 9.375MHz to 14.0625MHz.
Crystal Oscill ator Parameters for ASK Operation
Figure 2 shows a reference oscillator circuit
configuration for ASK operation. The reference oscillator
can drive cr ystals with an ESR range from 20Ω to 300Ω.
When the ESR of the crystal is at 20Ω, the crystal
parameter limits are:
ESR 20Ω
CPAR 2 to 10pF
CMO 10 to 40fF
Figure 2. Reference Oscillator ASK Operation
When the ESR of the crystal is at 300Ω, the crystal
parameter limits are:
ESR 300Ω
CPAR 2 to 5pF
CMO 10 to 40fF
CLOAD 10 to 30pF
Micrel, Inc.
MICRF112
Febr
uary 2013 12 M9999-020713
Crystal Oscillator for FSK Operation
Figure 3 shows the reference oscillator circuit
configuration for FSK operation. To operate the
MICRF112 in FSK mode, one additional capacitor is
needed between XTLOUT pin and the XTAL_MOD pin.
Crystal parameters for FSK operation are the same as
for ASK operation except:
• When the ESR of crystal is at 20Ω,
CFSK + CLOAD must not exceed 70pF.
• When the ESR of crystal is at 300Ω,
CFSK + CLOAD must not exceed 30pF.
Figure 3. Reference Oscillator FSK Operation
PLL×32
The function of PLL×32 is to provide a stable carrier
frequenc y for tra nsmis sion. It is a “divided by 32” phase-
locked oscillator.
Power Amplifier
The power amplifier serves two purposes: to buffer the
VCO from external elements and to amplify the phase-
lock ed signal. T he power am plifier can prod uce +10d Bm
at 3V (typical).
Enable Control
The enable control gates the ASK data. It only allows
transmission when Lock, Amplitude, and Undervoltage
Detect conditions are valid.
Undervoltage Detect
The undervoltage detect bl oc k sens es operati ng vo lta ge.
If the operating voltage falls below 1.6V, the
undervoltage detect block sends a signal to the enable
control block to disable the PA.
Open-Drai n Swit ch
The open-drain switch is used for FSK operation. FSK
data is fed int o the FS K pi n . The FSK pin is c onn ected to
the gate of the open-drain switch. The open collector is
connected to the XTAL_MOD pin. In Figure 3, a
capacitor is shown connected from the XTAL_MOD pin
to XTLOUT. When the FSK pin goes high, the capacitor
between XTAL_MOD and XTLOUT pulls the frequency
of REFOSC low.
Micrel, Inc.
MICRF112
Febr
uary 2013 13 M9999-020713
Application Information
Figure 4. ASK 433.92MHz and 315MHz (MSOP)
Note: Val ues in parenthesis are f or 315MHz.
The MICRF112 is ideal for driving a 50Ω source
monopole or a l oop ant enn a. Fig ur e 4 is an ex ample o f a
loop antenna configuration. Figure 4 also shows both
315MHz and 433.92MHz ASK configurations for a loop
antenna. In addition t o using a dif ferent cr ys tal, modifi ed
values are needed for certain frequencies. These are
listed in Table 1.
Frequency
(MHz) L1
(nH) C5
(pF) L4
(nH) C7
(pF) Y1
(MHz)
315.0 470 10 150 6.8 9.84375
433.92 680 10 82 4.7 13.5600
Table 1. Modified Frequency Values
The ref erence design show n in Figure 4 has an antenna
optimized for using the matching network, as described
in Table 1.
Power Control Using an Extern al Resistor
R7 is used to adjust the RF output levels that may be
needed to meet compliance. As an example, Tables 2
and 3 list typical values of conducted RF output levels
and corresponding R7 resistor values for the 50Ω test
board shown in the Test Circuit.
R7, Ω
Output Power, dBm
IDD, mA
0 10 6.7
75 8.5 6.3
100 8.0 6.2
500 1.6 4.13
1000 −3.8 4.87
Table 2. ASK Output Power at 1Kbps (Manchester) vs.
External Resistor at 315MHz
R7, Ω
Output Power, dBm
IDD, mA
0 8.68 7.5
75 8.34 7.33
100 8.02 7.3
500 4.34 6.3
1000 0.42 5.5
Table 3. ASK Output Power at 1Kbps (Manchester) vs.
External Resistor at 433.92MHz
Micrel, Inc.
MICRF112
Febr
uary 2013 14 M9999-020713
Output Matching Network
Part of the funct ion of the outp ut network is to attenuate
the second and third harmonics. When matching to a
transmit frequency, be sure not only to optimize for
maximum output power but to attenuate unwanted
harmonics.
Layout Is sues
PCB layout is extremely important to achieve optimum
performance and consistent manufacturing results. Be
careful with the orientation of the components to ensure
that they do not couple or decouple the RF signal. PCB
trace length should be short, to minimize parasitic
inductance (1in ~ 20nH). For example, depending on
inductance values, a 0.5in trace can change the
inductance by as much as 10%. To reduce parasitic
inductance, the use of wide traces and a ground plane
under signal traces is recommended. Use vias with low
value inductance for components requiring a connection
to ground.
Antenna Layout
The antenna trace layout affects directivity. No ground
plane sh ould be under the antenna trace. For cons istent
performance, do not place components inside the loop of
the anten na. Ger b ers f or the Evaluation Board PCB, with
a suggested layout are available on the Micrel web site
at: www.micrel.com.
Micrel, Inc.
MICRF112
Febr
uary 2013 15 M9999-020713
Demo Board PCB Layout
Assembly Drawing
MICRF112 Evaluation Board (MSOP)
Top Layer
MICRF112 Evaluation Bo ard (MSOP)
Bottom Layer
MICRF112 Evaluation Board (MSOP)
Micrel, Inc.
MICRF112
Febr
uary 2013 16 M9999-020713
Evaluation Board Schematic
Figure 5. TX112-1 Evaluation Board Schematic (MSOP)
Note: Confi gurat i on is for ASK operation. Values in parenthesis are for 315MHz.
Functional Description of the TX112-1
Evaluation Board
The layout of the TX112-1 Evaluation Board PCB is
shown on page 15. Figure 5 is a detailed schematic of
the TX112-1. Components labeled “NP” use different
configurations for FSK operation. Table 2 describes
each header pin connector used in the evaluation board.
Pin
Function Name
Functional Description
J1-1 VDD 1.8V to 3.6V
J1-2 Ground VSS
J1-3 ASK INPUT Modulating Data Input, ASK or FSK
J2-1 REF-OSC External Reference Input
J2-2 GROUND VSS
J2-3 ENABLE Enable Input, Active High
Table 4. Header Pin Connectors
Micrel, Inc.
MICRF112
Febr
uary 2013 17 M9999-020713
TX112-1-433.92 ASK Bill of Materials
Item Part Number Manufacturer Description Qty.
C1 GRM21BR60J106KE01L Murata
(1)
10µF Capacitor, 0805 1
C2 GRM1885C1H101JA01D Murata 100pF Capacitor, 0603 1
C5 GRM1885C1H100JA01D Murata 10pF Capacitor, 0603 1
R1,R4,R6 3
C6,C8,C11,C12,C15 5
C7 GRM1885C1H4R7JA01D Murata 4.7pF Capacitor, 0603 1
C10 GRM188F51H104ZA01D Murata 0.1µF Capacitor, 0603 1
C13,C14 GRM1885C1H180JA01D Murata 18pF Capacitor, 0603 2
J1,J2 TSHR-114-S-02-A-GT CON3 2
L1 0805CS-680XJB Coilcraft
(2)
470nH Inductor, 0805 1
L4 0603CS-082NXJB Coilcraft 150nH Inductor , 060 3 1
L5 ANTENNA LOOP, Part of PCB Antenna 1
R2 CRCW0603100KFKEA Vishay
(3)
100kΩ Resistor, 0603 1
R3,R5,R7
R8,JPR1,JPR2 CRC06030000Z0EA Vishay 0Ω Resistor, 0603 6
U1 MICRF112YMM Micrel(4) 300MHz to 450MHz, +10dBm
ASK/FSK Transmitter with
Shutdown 1
Y1 SA-13.5600-F-10-C-3-3 HIB
(5)
13.560MHz XTAL 1
Notes:
1. Murata Tel: www.murata.com.
2. Coilcraft: www.coilcraft.com.
3. Vishay Tel: www.vishay.com
4. Micrel, Inc.: www.micrel.com.
5. HIB: www.hib.com.br.
Micrel, Inc.
MICRF112
Febr
uary 2013 18 M9999-020713
Tx112-1-315M Hz ASK Bill of Materials
Item Part Number Manufacturer Description Qty.
C1 GRM21BR60J106KE01L Murata
(1)
10µF Capacitor, 0805 1
C2 GRM1885C1H101JA01D Murata 100pF Capacitor, 0603 1
C5 GRM1885C1H1000JA01D Murata 10pF Capacitor, 0603 1
R1,R4,R6 3
C6,C8,C11,C12,C15 5
C7 GRM1885C1H6R8JA01D Murata 4.7pF Capacitor, 0603 1
C10 GRM188F51H104ZA01D Murata 0.1µF Capacitor, 0603 1
C13,C14 GRM1885C1H180JA01D Murata 18pF Capacitor, 0603 2
J1,J2 TSHR-114-S-02-A-GT CON3 2
L1 0805CS-470XJB Coilcraft
(2)
470nH Inductor, 0805 1
L4 0603CS-R15XJB Coilcraft 150nH Inductor, 0603 1
L5 ANTENNA LOOP, Part of PCB Antenna 1
R2 CRCW0603100KFKEA Vishay
(3)
100kΩ Resistor, 0603 1
R3,R5,R7
R8,JPR1,JPR2 CRC06030000Z0EA Vishay 0Ω Resistor, 0603 6
U1 MICRF112YMM Micrel(4) 300MHz to 450MHz, +10dBm
ASK/FSK Transmitter with
Shutdown 1
Y1 SA-9.84375-F-10-C-3-3 HIB
(5)
9.84375MHz XTAL 1
Notes:
1. Murata Tel: www.murata.com.
2. Coilcraft: www.coilcraft.com.
3. Vishay Tel: www.vishay.com.
4. Micrel, Inc.: www.micrel.com.
5. HIB: www.hib.com.br.
Micrel, Inc.
MICRF112
Febr
uary 2013 19 M9999-020713
FSK Operation
The Bill of Materials tables describe the components needed for AS K oper a tio n for 433.92MHz and 315MHz.
Table 5 l ists the com ponent values that chang e between ASK and FSK operation. Note that use of a high F SK data rat e
may excite par asitic res onant modes with som e crystal types. Recomm ended cr ystals from the Bil l of Material s tables are
good for both ASK and FSK.
Mode R1 R2 R5 R6 JPR1 JPR2 C8
ASK NP 100kΩ 0Ω NP 0Ω NP NP
FSK 0Ω NP NP 100kΩ NP 0Ω 3.3pF
(1)
10pF(2)
Notes:
1. C8 = 3.3pF for 1kHz using HC49/U or HC49US type crystals.
2. C8= 10pF for 10kHz using HC49/U, (high profile) only.
Table 5. ASK and FSK Settings
R3
R4
Constant ON 0Ω NP
External Standby Control NP 100kΩ
Table 6. Enable Control (Shutdown)
Micrel, Inc.
MICRF112
Febr
uary 2013 20 M9999-020713
Package Information(1)
10-Pin MSOP Package Type (YMM)
Note: T he Pin1 marki ng symbol could be a circl e, triangle, or other sym bol. P ackage information is c orrect as of t he publication date. For updates and
most current information, go to www.micrel.com.
Micrel, Inc.
MICRF112
Febr
uary 2013 21 M9999-020713
Package Information(1) (Continued)
10-Pin Ultra-Thin DFN 2mm x 2mm x 0.4mm (MU)
Note: T he Pin1 marki ng symbol could be a circl e, triangle, or other symbol. Package informat ion is correct as of the publication dat e. For updates and
most current information, go to www.micrel.com.
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
Micrel makes no represent ations or warranties with respec t t o the accuracy or completeness of the information furnis hed in t his data sheet. This
informat i on is not intended as a warranty and Micrel does not assume responsibilit y for its use. Micrel reserves the right to change circuitry,
specificat i ons and descript i ons at any time without notice. No license, whether express , im plied, arisi ng by estoppel or otherwise, t o any intellectual
property rights is granted by this document. Except as provided in Micrel’s terms and condit i ons of sale for such products, Micrel assum es no liabil ity
whatsoever, and Micrel disclaims any express or impli ed warranty relati ng to t he sale and/or use of Micrel products i ncludi ng liabi l ity or warranties
relating to fitness for a partic ular purpose, merchant abi lit y, or inf ri ngem ent of any patent, copyright or other intel l ect ual propert y right.
Micrel Products are not designed or authorized for use as components in life support applianc es, devic es or syst ems where malfuncti on of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or syst ems that (a) are intended for surgical
implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant inj ury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or
systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Mic rel for any damages resulting from such use or sale.
© 2013 Micrel, Incorporated.
