19-3707; Rev 1; 9/08
Low-Cost, 308MHz, 315MHz, and 433.92MHz
FSK Transceiver with Fractional-N PLL
General Description
The MAX7031 crystal-based, fractional-N transceiver is
designed to transmit and receive FSK data at factory-
preset carrier frequencies of 308MHz
†
, 315MHz, or
433.92MHz with data rates up to 33kbps (Manchester
encoded) or 66kbps (NRZ encoded). This device gen-
erates a typical output power of +10dBm into a 50Ω
load, and exhibits typical sensitivity of -110dBm. The
MAX7031 features separate transmit and receive pins
(PAOUT and LNAIN) and provides an internal RF switch
that can be used to connect the transmit and receive
pins to a common antenna.
The MAX7031 transmit frequency is generated by a 16-
bit, fractional-N, phase-locked loop (PLL), while the
receiver’s local oscillator (LO) is generated by an inte-
ger-N PLL. This hybrid architecture eliminates the need
for separate transmit and receive crystal reference
oscillators because the fractional-N PLL is preset to be
10.7MHz above the receive LO. Retaining the fixed-N
PLL for the receiver avoids the higher current-drain
requirements of a fractional-N PLL and keeps the
receiver current drain as low as possible.
The fractional-N architecture of the MAX7031 transmit
PLL allows the transmit FSK signal to be preset for
exact frequency deviations, and completely eliminates
the problems associated with oscillator-pulling FSK sig-
nal generation. All frequency-generation components
are integrated on-chip, and only a crystal, a 10.7MHz IF
filter, and a few discrete components are required to
implement a complete antenna/digital data solution.
The MAX7031 is available in a small, 5mm x 5mm, 32-
pin, thin QFN package, and is specified to operate in
the automotive -40°C to +125°C temperature range.
†
Consult factory for availability.
Features
♦
+2.1V to +3.6V or +4.5V to +5.5V Single-Supply
Operation
♦
Single-Crystal Transceiver
♦
Factory-Preset Frequency (No Serial Interface
Required)
♦
FSK Modulation
♦
Factory-Preset FSK Frequency Deviation
♦
+10dBm Output Power into 50Ω Load
♦
Integrated TX/RX Switch
♦
Integrated Transmit and Receive PLL, VCO, and
Loop Filter
♦
> 45dB Image Rejection
♦
Typical RF Sensitivity*: -110dBm
♦
Selectable IF Bandwidth with External Filter
♦
RSSI Output with High Dynamic Range
♦
< 12.5mA Transmit-Mode Current
♦
< 6.7mA Receive-Mode Current
♦
< 800nA Shutdown Current
♦
Fast-On Startup Feature, < 250µs
♦
Small, 32-Pin, Thin QFN Package
*0.2%
BER, 4kbps Manchester-encoded data, 280kHz IF BW
MAX7031
Ordering Information
PART
MAX7031_ATJ__
TEMP RANGE
-40°C to +125°C
PIN-PACKAGE
32 Thin QFN-EP**
Applications
2-Way Remote Keyless Entry
Security Systems
Home Automation
Remote Controls
Remote Sensing
Smoke Alarms
Garage-Door Openers
Local Telemetry Systems
**EP
= Exposed pad.
Note:
The MAX7031 is available with factory-preset operating
frequencies. See the Selector Guide for complete part num-
bers.
Pin Configuration, Selector Guide, Typical Application
Circuit, and Functional Diagram appear at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Low-Cost, 308MHz, 315MHz, and 433.92MHz
FSK Transceiver with Fractional-N PLL
MAX7031
ABSOLUTE MAXIMUM RATINGS
HV
IN
to GND..........................................................-0.3V to +6.0V
PAV
DD
, AV
DD
, DV
DD
to GND ................................-0.3V to +4.0V
ENABLE, T/R, DATA, AGC0, AGC1,
AUTOCAL to GND ................................-0.3V to (HVIN + 0.3)V
All Other Pins to GND ..............................-0.3V to (_VDD + 0.3)V
Continuous Power Dissipation (T
A
= +70°C)
32-Pin Thin QFN (derate 21.3mW/°C
above +70°C).............................................................1702mW
Operating Temperature Range .........................-40°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
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
(Typical
Application Circuit,
50Ω system impedance, PAV
DD
= AV
DD
= DV
DD
= HV
IN
= +2.1V to +3.6V, f
RF
= 308MHz, 315MHz, or
433.92MHz, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at PAV
DD
= AV
DD
= DV
DD
= HV
IN
= +2.7V, T
A
= +25°C,
unless otherwise noted.) (Note 1)
PARAMETER
Supply Voltage (3V Mode)
Supply Voltage (5V Mode)
SYMBOL
V
DD
HV
IN
CONDITIONS
HV
IN
, PAV
DD
, AV
DD
, and DV
DD
connected
to power supply
PAV
DD
, AV
DD
, and DV
DD
unconnected
from HV
IN
, but connected together
Transmit mode
(Note 2)
T
A
< +85°C,
typ at +25°C
(Note 3)
f
RF
= 315MHz
f
RF
= 434MHz
Receiver 315MHz
Receiver 434MHz
Deep-sleep (3V mode)
Deep-sleep (5V mode)
Receiver 315MHz
T
A
< +125°C,
typ at +125°C
(Note 2)
Voltage Regulator
DIGITAL I/O
Input-High Threshold
Input-Low Threshold
Pulldown Sink Current
Output Low Voltage
Output High Voltage
V
OL
V
OH
V
IH
V
IL
(Note 2)
(Note 2)
AGC0-1, AUTOCAL, ENABLE, T/R, DATA
(HV
IN
= 5.5V)
I
SINK
= 500µA
I
SOURCE
= 500µA
20
0.15
HV
IN
- 0.26
0.9
x HV
IN
0.1
x HV
IN
V
V
µA
V
V
V
REG
Receiver 434MHz
Deep-sleep (3V mode)
Deep-sleep (5V mode)
HV
IN
= 5V, I
LOAD
= 15mA
MIN
2.1
4.5
TYP
2.7
5.0
11.6
12.4
6.4
6.7
0.8
2.4
6.8
7.0
8.0
14.9
3.0
MAX
3.6
5.5
19.1
20.4
8.4
8.7
8.8
10.9
8.7
8.8
34.2
39.3
µA
mA
µA
V
mA
UNITS
V
V
Supply Current
I
DD
2
_______________________________________________________________________________________
Low-Cost, 308MHz, 315MHz, and 433.92MHz
FSK Transceiver with Fractional-N PLL
AC ELECTRICAL CHARACTERISTICS
(Typical
Application Circuit,
50Ω system impedance, PAV
DD
= AV
DD
= DV
DD
= HV
IN
= +2.1V to +3.6V, f
RF
= 308MHz, 315MHz. or
433.92MHz, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at PAV
DD
= AV
DD
= DV
DD
= HV
IN
= +2.7V, T
A
= +25°C,
unless otherwise noted.) (Note 1)
PARAMETER
GENERAL CHARACTERISTICS
Frequency Range
Maximum Input Level
Transmit Efficiency (Note 5)
P
RFIN
f
RF
= 315MHz
f
RF
= 434MHz
ENABLE or T/R transition low to high,
transmitter frequency settled to within
50kHz of the desired carrier
ENABLE or T/R transition low to high,
transmitter frequency settled to within 5kHz
of the desired carrier
ENABLE transition low to high, or T/R
transition high to low, receiver startup time
(Note 4)
RECEIVER
0.2% BER, 4kbps
Manchester data rate,
280kHz IF BW, FSK
±50kHz deviation
315MHz
434MHz
-110
dBm
-107
46
T
A
= +25°C (Note 3)
Output Power
P
OUT
T
A
= +125°C, PAV
DD
= AV
DD
= DV
DD
=
HV
IN
= +2.1V (Note 2)
T
A
= -40°C, PAV
DD
= AV
DD
= DV
DD
= HV
IN
= +3.6V (Note 3)
Maximum Carrier Harmonics
Reference Spur
PHASE-LOCKED LOOP
Transmit VCO Gain
Transmit PLL Phase Noise
Receive VCO Gain
Receive PLL Phase Noise
Loop Bandwidth
10kHz offset, 500kHz loop BW
1MHz offset, 500kHz loop BW
Transmit PLL
Receive PLL
K
VCO
10kHz offset, 200kHz loop BW
1MHz offset, 200kHz loop BW
340
-68
-98
340
-80
-90
200
500
MHz/V
dBc/Hz
MHz/V
dBc/Hz
kHz
With output matching network
4.6
3.9
10.0
6.7
13.1
-40
-50
15.8
dBc
dBc
15.5
dBm
dB
308/315/433.92
0
32
30
200
MHz
dBm
%
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX7031
Power-On Time
t
ON
350
µs
250
Sensitivity
Image Rejection
POWER AMPLIFIER
_______________________________________________________________________________________
3
Low-Cost, 308MHz, 315MHz, and 433.92MHz
FSK Transceiver with Fractional-N PLL
MAX7031
AC ELECTRICAL CHARACTERISTICS (continued)
(Typical
Application Circuit,
50Ω system impedance, PAV
DD
= AV
DD
= DV
DD
= HV
IN
= +2.1V to +3.6V, f
RF
= 308MHz, 315MHz. or
433.92MHz, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at PAV
DD
= AV
DD
= DV
DD
= HV
IN
= +2.7V, T
A
= +25°C,
unless otherwise noted.) (Note 1)
PARAMETER
Reference Frequency Input Level
LOW-NOISE AMPLIFIER/MIXER (Note 7)
LNA Input Impedance
Z
INLNA
Normalized to 50Ω
High-gain state
Voltage-Conversion Gain
Low-gain state
Input-Referred 3rd-Order
Intercept Point
Mixer Output Impedance
LO Signal Feedthrough to
Antenna
RSSI
Input Impedance
Operating Frequency
3dB Bandwidth
Gain
FSK DEMODULATOR
Conversion Gain
ANALOG BASEBAND
Maximum Data Filter Bandwidth
Maximum Data Slicer Bandwidth
Maximum Peak Detector
Bandwidth
Maximum Data Rate
CRYSTAL OSCILLATOR
Crystal Frequency
Maximum Crystal Inductance
Frequency Pulling by V
DD
Crystal Load Capacitance
(Note 6)
f
XTAL
(f
RF
- 10.7)
/ 24
50
2
4.5
MHz
mH
ppm/V
pF
Manchester coded
Nonreturn to zero (NRZ)
50
100
50
33
66
kHz
kHz
kHz
kbps
2.0
mV/kHz
f
IF
330
10.7
10
15
Ω
MHz
MHz
mV/dB
IIP3
High-gain state
Low-gain state
f
RF
= 315MHz
f
RF
= 434MHz
f
RF
= 315MHz
f
RF
= 434MHz
f
RF
= 315MHz
f
RF
= 434MHz
1 - j4.7
1 - j3.3
50
45
13
9
-42
-6
330
-100
dBm
Ω
dBm
dB
SYMBOL
CONDITIONS
MIN
TYP
0.5
MAX
UNITS
V
P-P
4
_______________________________________________________________________________________
Low-Cost, 308MHz, 315MHz, and 433.92MHz
FSK Transceiver with Fractional-N PLL
AC ELECTRICAL CHARACTERISTICS (continued)
(Typical
Application Circuit,
50Ω system impedance, PAV
DD
= AV
DD
= DV
DD
= HV
IN
= +2.1V to +3.6V, f
RF
= 308MHz, 315MHz. or
433.92MHz, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at PAV
DD
= AV
DD
= DV
DD
= HV
IN
= +2.7V, T
A
= +25°C,
unless otherwise noted.) (Note 1)
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Supply current, output power, and efficiency are greatly dependent on board layout and PAOUT match.
100% tested at T
A
= +125°C. Guaranteed by design and characterization over temperature.
Guaranteed by design and characterization. Not production tested.
Time for final signal detection; does not include baseband filter settling.
Efficiency = P
OUT
/(V
DD
x I
DD
).
Dependent on PCB trace capacitance.
Input impedance is measured at the LNAIN pin. Note that the impedance at 315MHz includes the 12nH inductive degenera-
tion from the LNA source to ground. The impedance at 434MHz includes a 10nH inductive degeneration connected from the
LNA source to ground. The equivalent input circuit is 50Ω in series with ~2.2pF. The voltage conversion is measured with
the LNA input-matching inductor, the degeneration inductor, and the LNA/mixer tank in place, and does not include the IF
filter insertion loss.
MAX7031
Typical Operating Characteristics
(Typical
Operating Circuit,
PAV
DD
= AV
DD
= DV
DD
= HV
IN
= +3.0V, f
RF
= 433.92MHz, IF BW = 280kHz. 4kbps Manchester
encoded, 0.2% BER deviation = ±50kHz, T
A
= +25°C, unless otherwise noted.)
RECEIVER
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX7031 toc01
SUPPLY CURRENT vs. RF FREQUENCY
FSK MODE
MAX7030 toc02
DEEP-SLEEP CURRENT vs. TEMPERATURE
16
DEEP-SLEEP CURRENT (µA)
14
12
10
8
6
4
2
V
CC
= +3.6V
V
CC
= +3.0V
V
CC
= +2.1V
MAX7031 toc03
7.4
7.2
SUPPLY CURRENT (mA)
7.0
6.8
6.6
+25°C
6.4
-40°C
6.2
6.0
2.1
2.4
2.7
3.0
3.3
+85°C
+125°C
7.0
6.9
SUPPLY CURRENT (mA)
6.8
6.7
+25°C
6.6
6.5
6.4
-40°C
+85°C
+125°C
18
0
300
325
350
375
400
425
450
-40
-15
-10
35
60
85
110
RF FREQUENCY (MHz)
TEMPERATURE (°C)
3.6
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
5
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