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MICRF112 QwikRadio(R) UHF ASK/FSK Transmitter
General Description
The MICRF112 is a high performance, easy to use, single chip ASK / FSK Transmitter IC for remote wireless applications in the 300 to 450MHz frequency band. This transmitter IC is a true "data-in, antenna-out" monolithic device. MICRF112 is high performance in three areas: power delivery, operating voltage, and operating temperature. In terms of power, the MICRF112 is capable of delivering +10 dBm into a 50 load. This power level enables a small form factor transmitter (lossy antenna) such as a key fob transmitter to operate near the maximum limit of transmission regulations. In terms of operating voltage, the MICRF112 operates from 3.6V to 1.8V. Many transmitter ICs in the same frequency band stop operating below 2.0V. The MICRF112 will work with most batteries to the end of their useful limits. In terms of operating temperature, the MICRF112 operates from -40C to +125C. This wide operating temperature range makes MICRF112 an ideal candidate for the demanding applications such as a tire pressure monitoring system. The MICRF112 is easy to use. One only needs a reference frequency (RF carrier frequency divided by 32 times) generated from a crystal with a few additional external parts to create a complete versatile transmitter. The MICRF112 operates with ASK/OOK (Amplitude Shift Keying/On-Off Keyed) UHF receiver types from wide-band super-regenerative radios to narrow-band, high performance super-heterodyne receivers. The MICRF112's maximum ASK data rate is 50kbps (Manchester Encoding). It operates with FSK receivers as well. The chip is designed to support narrow band FSK (Frequency Shift Modulation) by switching an external capacitor in parallel with the reference crystal. The MICRF112's maximum FSK data rate is 10kbps.
Features
* * * * * * * * Complete UHF transmitter Frequency range 300MHz to 450MHz Data rates up to 50kbps ASK, 10kbps FSK Output Power to 10dBm Low external part count Low standby current <1A Low voltage operation (down to 1.8V) Operate with crystals or ceramic resonators
Applications
* * * * * * Remote Keyless Entry Systems (RKE) Remote Control (STB, HVAC and Appliances) Garage Door Opener Transmitters Remote Sensor Data Links Infrared Transmitter Replacement Tire Pressure Monitor System (TPMS)
Ordering Information
Part Number MICRF112YMM10 Temp. Range -40C to +125C Package 10-Pin MSOP
QwikRadio is a registered trademark 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
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MICRF112
Typical Application
Figure 1. MICRF112 ASK Key Fob Design
Note: Values in parenthesis are for 315MHz
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MICRF112
Pin Configuration
ASK XTLIN XTLOUT VSS XTAL_MOD 1 2 3 4 5 10 VDD 9 PAOUT 8 VSSPA 7 EN 6 FSK
10-Pin MSOP (M)
Pin Description
Pin Number MSOP-10 1 2 3 4 5 6 7 8 9 10 Pin Name ASK XLIN XTLOUT VSS XTAL_MOD FSK EN VSSPA PA_OUT VDD Pin Function ASK DATA Input Reference oscillator input connection. Reference oscillator output connection. Ground Reference oscillation modulation port for FSK operation. FSK Data Input Chip enable, active high PA Ground PA output Positive Power Supply
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MICRF112
Absolute Maximum Ratings (Note 1)
Supply Voltage VDD ................................................... +5.0V Voltage on PAOUT ..................................................... +7.2V Voltage on I/O Pins.............................VSS-0.3 to VDD+0.3 Storage Temperature Range.................... -65C to + 150C Lead Temperature (soldering, 10 seconds) ............+ 300C ESD Rating ................................................................ Note 3
Operating Ratings (Note 2)
Supply Voltage VDD......................................... 1.8V to 3.6V Ambient Operating Temperature (TA).......-40C to +125C Programmable Transmitter Frequency Range: ....................................................... 300MHz to 450MHz
Electrical Characteristics(Note 4)
Specifications apply for VDD = 3.0V, TA = 25C, FreqREFOSC = 13.560MHz, EN = VDD. Bold values indicate -40C to 125C unless otherwise noted. 1kbps data rate 50% duty cycle. RL 50ohm load (matched) Parameter Power Supply Standby supply current, Iq Mark Supply Current ION SPACE supply current, IOFF EN = VSS @ 315MHz, POUT = +10dBm @ 433.92MHz, POUT = +10dBm @ 315MHz @ 433.92 MHz RF Output Section and Modulation Limits: Output power level, POUT FSK or ASK "mark" Harmonics output for 315 MHz Harmonics output for 433.92 MHz Extinction ratio for ASK FSK Modulation Frequency Deviation Data Rate ASK Modulation Data Rate Occupied Bandwidth VCO Section 315 MHz Single Side Band Phase Noise 433.92 MHz Single Side Band Phase Noise Reference Oscillator Section XTLIN, XTLOUT, XTLMOD External Capacitance Oscillator Startup Time
Note 5
Condition
Min
Typ .05 12.3 12.5 2 2 10 10 -39 -53 -55 -55 70
Max 1A
Units A mA mA mA mA dBm dBm dBc dBc dBc dBc dBc kHz
@315MHz, @ 630MHz, @945MHz,
Note 4 Note 4
@433.92MHz,
Note 4 Note 4
2nd harm. 2nd harm. 3rd harm.
3rd harm.
@ 867.84MHz, @1301.76MHz,
Note 4 Note 4
load capacitor = 10pF, crystal type = HC49/U
22 10 50
kbps kbps kHz kHz dBc/Hz dBc/Hz dBc/Hz dBc/Hz pF pF s
@315MHz, Note 6 @433.92MHz, Note 6 @ 100kHz from Carrier @ 1000kHz from Carrier @ 100kHz from Carrier @ 1000kHz from Carrier Pin capacitance See Schematic C17 & C18 Crystal: HC49S
<700 <1000 -76 -79 -72 -81 2 18 300
Digital / Control Section Output Blanking STDBY transition from LOW to HIGH 500 s
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MICRF112
Electrical Characteristics (cont.)
Parameter Digital Input (EN, ASK and FSK) Digital Input Leakage Current (EN, ASK and FSK Pins) Under Voltage Lock Out (UVLO)
Note 1. Exceeding the absolute maximum rating may damage the device. Note 2. The device is not guaranteed to function outside its operating rating. Note 3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. Note 4. Measured using Test Circuit in Figure 2. Note 5. Dependent on crystal Note 6. RBW = 100kHz, OBW measured at -20dBc.
Condition High (VIH) Low (VIL) High (VIH) Low (VIL)
Min 0.8xVDD
Typ
Max
0.2xVDD
Units V V A A V
0.05 0.05 1.6
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MICRF112
Test Circuit
Figure 2. MICRF112 Test Circuit with 50 Output
Note 1. Values without parenthesis are for 433.92 MHz and values in parenthesis are for 315MHz Note 2. C9 = 100pF for external REF-OSC Note 3. For FSK R1 = 0, R2 = NP, R6 = 100k, and R5 = NP
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MICRF112
Assembly Drawing MICRF112 50 Ohm Test Board
Top Layer MICRF112 50 Ohm Test Board
Bottom Layer MICRF112 50 Ohm Test Board
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Typical Characteristics Using MICRF112, 50 test Board
315MHz OBW, ASK = 1kHz 315Mhz OBW, ASK = 50kHz
CW Max Power @ 3V, 315MHz, ASK = 1kHz, Note 1
RF Spectrum 2 Harmonic; Fundamental at 315 MHz
nd
RF Spectrum 3 Harmonic; Fundamental at 315 MHz
rd
315MHz, Power Level at Space, VDD = 3.0V, ASK = 1kHz
Note 1. 1.2dB cable loss.
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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
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MICRF112
433.92MHz OBW, ASK = 1kHz
433.92MHz OBW, ASK = 50kHz
433.92MHz, CW Max Power @ 3V, ASK = 1kHz, Note 1
RF Spectrum 2 Harmonic; Fundamental at 433.92 MHz
nd
RF Spectrum 3 Harmonic; Fundamental at 433.92 MHz
rd
433.92MHz Power Level at Space, VDD = 3.0V, ASK = 1kHz
Note 1. 1.3dB cable loss.
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MICRF112
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/Hz
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MICRF112
Functional Diagram
Figure 3. Functional Block Diagram MICRF112 10 Pin ASK / FSK Version
Functional Description
Figure 3 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, PLLx32, power amplifier, enable control, under voltage detect and open drain switch for FSK operation. Crystal Oscillator The reference oscillator is crystal-based Pierce configuration. It is designed to accept crystals with frequency from 9.375MHz to 14.0625MHz. Crystal Oscillator Parameters for ASK Operation Figure 4 shows a reference oscillator circuit configuration for ASK operation. The reference oscillator is capable of driving crystals with ESR range from 20 to 300. When the ESR of crystal is at 20, the crystal parameter limits are: ESR 20 CPAR 2 to 10pF CMO 10 to 40fF March 2007 12
Figure 4. Reference Oscillator ASK Operation
When the ESR of crystal is at 300, the crystal parameter limits are: ESR 300 CPAR 2 to 5pF CMO 10 to 40fF CLOAD 10 to 30pF
M9999-030107 (408) 944-0800
Micrel, Inc.
MICRF112
Crystal Oscillator for FSK Operation Figure 5 shows reference oscillator circuit configuration for FSK operation. To operate the MICRF112 in FSK mode, one additional capacitor is needed between XTALOUT pin and XTALMOD pin. Crystal parameters for FSK operation are the same as ASK operation except: * * When the ESR of crystal is at 20, CFSK + CLOAD not to exceed 70pF. When the ESR of crystal is at 300, CFSK + CLOAD not to exceed 30pF
Power Amplifier The power amplifier serves two purposes: 1) to buffer the VCO from external elements and 2) to amplify the phase locked signal. The power amplifier can produce +10dBm at 3V (typical). Enable Control Enable control gates the ASK data. It only allows transmission when Lock, Amplitude and Under Voltage Detect conditions are valid. Under Voltage Detect "Under voltage detect" block senses operating voltage. If the operating voltage falls below 1.6V, "under voltage detect" block will send a signal to "enable control" block to disable the PA. Open Drain Switch Open drain switch is used for FSK operation. FSK data is fed into the FSK pin. The FSK pin is connected to the gate of the open drain switch. The open collector is connected to the XTALMOD pin. In Figure 4, a capacitor is shown connected from XTALMOD pin to XTALOUT. When FSK pin goes high, the capacitor between XTALMOD and XTALOUT pulls the frequency of REFOSC low .
Figure 5. Reference Oscillator FSK Operation
PLL x32 The function of PLLx32 is to provide a stable carrier frequency for transmission. It is a "divided by 32" phase locked oscillator.
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MICRF112
Application Information
Figure 6. ASK 433.92MHz and 315MHz
Note: Values in parenthesis are for 315MHz
The MICRF112 is well suited to drive a 50 ohms source, monopole or a loop antenna. Figure 6 is an example of a loop antenna configuration. Figure 6 also shows both 315MHz and 433.92MHz ASK configurations for a loop antenna. Besides using a different crystal, Table 1 lists modified values needed for the listed frequencies.
Frequency (MHz) 315.0 433.92 L1 (nH) 470 680 C5 (pF) 10 10 Table 1 L4 (nH) 150 82 C7 (pF) 6.8 4.7 Y1 (MHz) 9.84375 13.5600
R7, 0 75 100 500 1000
Output Power, dBm 10 8.5 8.0 1.6 -3.8
IDD, mA 6.7 6.3 6.2 4.13 4.87
Output Power Versus External Resistor at 315MHz R7, 0 75 100 500 1000 Output Power, dBm 8.68 8.34 8.02 4.34 0.42 IDD, mA 7.5 7.33 7.3 6.3 5.5
The reference design shown in Figure 6 has an antenna optimized for using the matching network as described in Table 1. Power Control Using External Resistor R7 is used to adjust the RF output levels which may be needed to meet compliance. As an example, the following tables list typical values of conducted RF output levels and corresponding R7 resistor values for the 50 test board shown in Figure 2. R7 of the TX112 Demo board using the loop antenna can be adjusted for the appropriate radiated field allowed by FCC or ETSI compliance. Contact Micrel for suggested values to meet FCC and ETSI compliances.
Output Power Versus External Resistor at 433.92 MHz
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MICRF112 much as 10%. To reduce parasitic inductance, the use of wide traces and a ground plane under signal traces is recommended. Vias with low value inductance should be used for components requiring a connection-to-ground. Antenna Layout Directivity is affected by antenna trace layout. No ground plane should be under the antenna trace. For consistent performance, components should not be placed inside the loop of the antenna. Gerbers for Figure 7, with a suggested layout, can be obtained on the Micrel web site at: http://www.micrel.com.
Output Matching Network Part of the function of the output network is to attenuate the second and third harmonics. When matching to a transmit frequency, care must be taken not only to optimize for maximum output power but to attenuate unwanted harmonics. Layout Issues PCB Layout is of primary concern to achieve optimum performance and consistent manufacturing results. Care must used on orientation of components to ensure they do not couple or decouple the RF signal. PCB trace length should be short to minimize parasitic inductance, (1 inch ~ 20nH). For example, depending on inductance values, a 0.5 inch trace can change the inductance by as
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MICRF112
PCB Board
Assembly Drawing MICRF112 Demo Board
Top Layer MICRF112 Demo Board
Bottom Layer MICRF112 Demo Board
Figure 7. Demo Board PCB
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MICRF112
Figure 8. TX112-1 Demo Board Schematic
Note: Configuration is for ASK operation. Values in parenthesis are for 315MHz
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MICRF112 components labeled as NP are to obtain different configurations including FSK Mode of operation. Table 2 describes each header pin connector used in the demo board.
Functional Description of TX112-1 Evaluation Board.
Figure 7 shows the TX112-1 Demo Board PCB. Figure 8 is a detailed schematic of the TX112-1. Note that
Pin J1-1 J1-2 J1-3 J2-1 J2-2 J2-3
Function Name VDD Ground ASK INPUT REF-OSC GROUND ENABLE
Functional Description 1.8V to 3.6V VSS Modulating Data Input, ASK or FSK External Reference Input VSS Enable Input, Active High
TX112-1-433.92 ASK Bill of Materials
Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14 13 14 Quantity 1 1 1 3 5 1 1 2 2 1 1 1 1 6 1 1 Ref C1 C2 C5 R1,R4,R6 C6,C8,C11,C12,C15 C7 C10 C13,C14 J1,J2 L1 L4 L5 R2 R3,R5,R7 R8,JPR1,JPR2 U1 Y1 Part 10F 100pF 10pF (np) (np) 4.7pF 0.1F 18pF CON3 680nH 82nH ANTENNA 100k 0 MICRF112YMM10 13.560MHZ XTAL
Table 2
PCB Footprint 0805 0603 0603
Mfg P/N GRM21BR60J106KE01L GRM1885C1H101JA01D GRM1885C1H100JA01D
Manufacturer muRata muRata muRata
0603 0603 0603 0805 0603
0603 0603
GRM1885C1H4R7JA01D GRM188F51H104ZA01D GRM1885C1H180JA01D TSHR-114-S-02-A-GT 0805CS-680XJB 0603CS-082NXJB ANTENNA LOOP, Part of PCB CRCW0603100KFKEA CRC06030000Z0EA MICRF112YM SA-13.5600-F-10-C-3-3
muRata muRata muRata Coilcraft Coilcraft
Vishay Vishay Micrel HIB
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MICRF112
Tx112-1-315MHz ASK Bill of Materials
Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14 13 14 Quantity 1 1 1 3 5 1 1 2 2 1 1 1 1 6 1 1 Ref C1 C2 C5 R1,R4,R6 C6,C8,C11,C12,C15 C7 C10 C13,C14 J1,J2 L1 L4 L5 R2 R3,R5,R7 R8,JPR1,JPR2 U1 Y1 Part 10F 100pF 10pF (np) (np) 4.7pF 0.1F 18pF CON3 470nH 150nH ANTENNA 100k 0 MICRF112YMM10 9.84375MHZ XTAL
Table 3
PCB Footprint 0805 0603 0603
Mfg P/N GRM21BR60J106KE01L GRM1885C1H101JA01D GRM1885C1H1000JA01D
Manufacturer muRata muRata muRata
0603 0603 0603 0805 0603
0603 0603
GRM1885C1H6R8JA01D GRM188F51H104ZA01D GRM1885C1H180JA01D TSHR-114-S-02-A-GT 0805CS-470XJB 0603CS-R15XJB ANTENNA LOOP, Part of PCB CRCW0603100KFKEA CRC06030000Z0EA MICRF112YM SA-9.84375-F-10-C-3-3
muRata muRata muRata Coilcraft Coilcraft
Vishay Vishay Micrel HIB
FSK Operation
Table 2 and 3 describe the ASK operation for 433.92MHz and 315MHz. Table 4 lists the component values that change between ASK or FSK operation. Please note that use of a high FSK data rate may excite parasitic resonant modes with some crystal types. Recommended crystals from Table 2 and 3 are good for both ASK and FSK.
Mode ASK FSK R1 NP 0 R2 100k NP R5 0 NP R6 NP 100k JPR1 0 NP JPR2 NP 0 C8 NP (1)3.3pF (2)10pF
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 4: ASK and FSK Settings R3 Constant ON External Standby Control 0 NP R4 NP 100k
Table 5: Enable Control (Shutdown)
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MICRF112
Package Information
10-Pin MSOP Package Type (YMM10)
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
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems 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 injury to the user. A Purchaser's use or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser's own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. (c) 2007 Micrel, Incorporated.
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