Micrel MICRF112 Qwikradioâ® uhf ask/fsk transmitter Datasheet

MICRF112
QwikRadio® UHF ASK/FSK Transmitter
General Description
Features
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 50Ω 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 -40°C to
+125°C. 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.








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 <1µA
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
–40°C to +125°C
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
December 2011
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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
1
10 VDD
XTLIN
2
9 PAOUT
XTLOUT
3
8 VSSPA
VSS
4
7 EN
XTAL_MOD
5
6 FSK
10-Pin MSOP (M)
Pin Description
Pin Number
MSOP-10
Pin Name
1
ASK
ASK DATA Input
2
XLIN
Reference oscillator input connection.
3
XTLOUT
Pin Function
Reference oscillator output connection.
4
VSS
5
XTAL_MOD
Ground
6
FSK
FSK Data Input
7
EN
Chip enable, active high
Reference oscillation modulation port for FSK operation.
8
VSSPA
PA Ground
9
PA_OUT
PA output
10
VDD
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Positive Power Supply
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MICRF112
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
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 ....................-65°C to + 150°C
Lead Temperature (soldering, 10 seconds) ............ + 300°C
ESD Rating.................................................................Note 3
Supply Voltage VDD ........................................ 1.8V to 3.6V
Ambient Operating Temperature (TA) ...... –40°C to +125°C
Programmable Transmitter Frequency Range:
....................................................... 300MHz to 450MHz
Electrical Characteristics(Note 4)
Specifications apply for VDD = 3.0V, TA = 25°C, FreqREFOSC = 13.560MHz, EN = VDD. Bold values indicate –40°C to 125°C unless
otherwise noted. 1kbps data rate 50% duty cycle. RL 50ohm load (matched)
Parameter
Condition
Min
Typ
Max
Units
1µA
µA
Power Supply
Standby supply current, Iq
EN = VSS
.05
Mark Supply Current ION
@ 315MHz, POUT = +10dBm
11.2
@ 433.92MHz, POUT = +10dBm
11.2
mA
@ 315MHz
2.7
mA
@ 433.92 MHz
2.7
mA
@315MHz, Note 4
10.5
dBm
@433.92MHz, Note 4
10.5
dBm
-39
dBc
-53
dBc
-55
dBc
-55
dBc
70
dBc
SPACE supply current, IOFF
mA
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
@ 630MHz,
@945MHz,
Note 4
Note 4
2nd harm.
3rd harm.
@ 867.84MHz, Note 4 2nd harm.
@1301.76MHz,
Note 4
3rd harm.
Extinction ratio for ASK
FSK Modulation
Frequency Deviation
load capacitor = 10pF, crystal type = HC49/U
22
Data Rate
kHz
10
kbps
50
kbps
ASK Modulation
Data Rate
Occupied Bandwidth
@315MHz, Note 6
<700
kHz
@433.92MHz, Note 6
<1000
kHz
-76
dBc/Hz
VCO Section
315 MHz Single Side Band
Phase Noise
433.92 MHz Single Side
Band Phase Noise
@ 100kHz from Carrier
@ 1000kHz from Carrier
-79
dBc/Hz
@ 100kHz from Carrier
-72
dBc/Hz
@ 1000kHz from Carrier
-81
dBc/Hz
2
pF
Reference Oscillator Section
XTLIN, XTLOUT, XTLMOD
Pin capacitance
External Capacitance
See Schematic C17 & C18
18
pF
Oscillator Startup Time Note 5
Crystal: HC49S
300
µs
STDBY transition from LOW to HIGH
500
µs
Digital / Control Section
Output Blanking
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MICRF112
Electrical Characteristics (cont.)
Parameter
Condition
Min
Digital Input (EN, ASK and
FSK)
High (VIH)
0.8×VDD
Low (VIL)
Digital Input Leakage
Current
(EN, ASK and FSK Pins)
Typ
Max
Units
0.2×VDD
V
V
High (VIH)
0.05
µA
Low (VIL)
0.05
µA
1.6
V
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.
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MICRF112
Test Circuit
Figure 2. MICRF112 Test Circuit with 50Ω 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 = 0Ω, R2 = NP, R6 = 100k, and R5 = NP
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MICRF112
Assembly Drawing
Top Layer
MICRF112 50 Ohm Test Board
MICRF112 50 Ohm Test Board
Bottom Layer
MICRF112 50 Ohm Test Board
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MICRF112
Typical Characteristics Using MICRF112, 50Ω test Board
315MHz OBW, ASK = 1kHz
315Mhz OBW, ASK = 50kHz
CW Max Power @ 3V, 315MHz,
ASK = 1kHz, Note 1
RF Spectrum 2nd Harmonic;
Fundamental at 315 MHz
RF Spectrum 3rd Harmonic;
Fundamental at 315 MHz
315MHz, Power Level at Space,
VDD = 3.0V, ASK = 1kHz
Note 1. 1.2dB cable loss.
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MICRF112
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 2nd Harmonic;
Fundamental at 433.92 MHz
RF Spectrum 3rd Harmonic;
Fundamental at 433.92 MHz
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, PLL×32, 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.
Figure 4. Reference Oscillator ASK Operation
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 20Ω
to 300Ω.
When the ESR of crystal is at 20Ω, the crystal parameter
limits are:
ESR 20Ω
CPAR 2 to 10pF
CMO 10 to 40fF
December 2011
When the ESR of crystal is at 300Ω, the crystal
parameter limits are:
ESR
300Ω
2 to 5pF
CPAR
CMO
10 to 40fF
CLOAD
10 to 30pF
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MICRF112
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).
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 20Ω, CFSK + CLOAD
not to exceed 70pF.

When the ESR of crystal is at 300Ω, CFSK +
CLOAD not to exceed 30pF
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 ×32
The function of PLL×32 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)
L1
(nH)
C5
(pF)
L4
(nH)
C7
(p
Y1 (MHz)
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
Output Power Versus External Resistor at 315MHz
F)
315.0
470
10
150
6.8
9.84375
433.92
680
10
82
4.7
13.5600
Table 1
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 50Ω 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.
December 2011
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
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.
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
December 2011
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.
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MICRF112
PCB Board
Assembly Drawing
Top Layer
MICRF112 Demo Board
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
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
TX112-1-433.92 ASK Bill of Materials
PCB
Footprint
0805
0603
0603
Item
1
2
3
4
5
6
7
8
9
10
11
Quantity
1
1
1
3
5
1
1
2
2
1
1
Ref
C1
C2
C5
R1,R4,R6
C6,C8,C11,C12,C15
C7
C10
C13,C14
J1,J2
L1
L4
Part
10µF
100pF
10pF
(np)
(np)
4.7pF
0.1µF
18pF
CON3
680nH
82nH
12
13
1
1
ANTENNA
100kΩ
14
13
14
6
1
1
L5
R2
R3,R5,R7
R8,JPR1,JPR2
U1
Y1
0603
0603
0603
0805
0603
0603
0Ω
MICRF112YMM10
13.560MHZ XTAL
0603
Mfg P/N
GRM21BR60J106KE01L
GRM1885C1H101JA01D
GRM1885C1H100JA01D
Manufacturer
muRata
muRata
muRata
GRM1885C1H4R7JA01D
GRM188F51H104ZA01D
GRM1885C1H180JA01D
TSHR-114-S-02-A-GT
0805CS-680XJB
0603CS-082NXJB
ANTENNA LOOP, Part of
PCB
CRCW0603100KFKEA
muRata
muRata
muRata
CRC06030000Z0EA
MICRF112YM
SA-13.5600-F-10-C-3-3
Coilcraft
Coilcraft
Vishay
Vishay
Micrel
HIB
Table 2
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MICRF112
Tx112-1-315MHz ASK Bill of Materials
PCB
Footprint
0805
0603
0603
Item
1
2
3
4
5
6
7
8
9
10
11
Quantity
1
1
1
3
5
1
1
2
2
1
1
Ref
C1
C2
C5
R1,R4,R6
C6,C8,C11,C12,C15
C7
C10
C13,C14
J1,J2
L1
L4
Part
10µF
100pF
10pF
(np)
(np)
4.7pF
0.1µF
18pF
CON3
470nH
150nH
12
13
1
1
ANTENNA
100kΩ
14
13
6
1
L5
R2
R3,R5,R7
R8,JPR1,JPR2
U1
14
1
Y1
0603
0603
0603
0805
0603
0Ω
MICRF112YMM10
9.84375MHZ
XTAL
0603
Mfg P/N
GRM21BR60J106KE01L
GRM1885C1H101JA01D
GRM1885C1H1000JA01D
Manufacturer
muRata
muRata
muRata
GRM1885C1H6R8JA01D
GRM188F51H104ZA01D
GRM1885C1H180JA01D
TSHR-114-S-02-A-GT
0805CS-470XJB
0603CS-R15XJB
ANTENNA LOOP, Part of
PCB
CRCW0603100KFKEA
muRata
muRata
muRata
0603
Coilcraft
Coilcraft
Vishay
CRC06030000Z0EA
MICRF112YM
Vishay
Micrel
SA-9.84375-F-10-C-3-3
HIB
Table 3
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
R1
R2
R5
R6
JPR1
JPR2
C8
ASK
NP
100kΩ
0Ω
NP
0Ω
NP
NP
FSK
0Ω
NP
NP
100kΩ
NP
0Ω
(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
R4
Constant ON
0Ω
NP
External Standby Control
NP
100kΩ
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.
© 2011 Micrel, Incorporated.
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