General Description
The MAX7031 crystal-based, fractional-N transceiver is
designed to transmit and receive FSK data at factorypreset carrier frequencies of 308MHz†, 315MHz, or
433.92MHz with data rates up to 33kbps (Manchester
encoded) or 66kbps (NRZ encoded). This device generates 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 16bit, fractional-N, phase-locked loop (PLL), while the
receiver’s local oscillator (LO) is generated by an integer-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 signal 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, 32pin, thin QFN package, and is specified to operate in
the automotive -40°C to +125°C temperature range.
†
Consult factory for availability.
Applications
2-Way Remote Keyless Entry
Security Systems
Home Automation
Remote Controls
Remote Sensing
Smoke Alarms
Garage-Door Openers
Local Telemetry Systems
Features
o +2.1V to +3.6V or +4.5V to +5.5V Single-Supply
Operation
o Single-Crystal Transceiver
o Factory-Preset Frequency (No Serial Interface
Required)
o FSK Modulation
o Factory-Preset FSK Frequency Deviation
o +10dBm Output Power into 50Ω Load
o Integrated TX/RX Switch
o Integrated Transmit and Receive PLL, VCO, and
Loop Filter
o > 45dB Image Rejection
o Typical RF Sensitivity*: -110dBm
o Selectable IF Bandwidth with External Filter
o RSSI Output with High Dynamic Range
o < 12.5mA Transmit-Mode Current
o < 6.7mA Receive-Mode Current
o < 800nA Shutdown Current
o Fast-On Startup Feature, < 250µs
o Small, 32-Pin, Thin QFN Package
MAX7031
Low-Cost, 308MHz, 315MHz, and 433.92MHz
FSK Transceiver with Fractional-N PLL
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
19-3707; Rev 3; 11/10
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.
*
0.2% BER, 4kbps Manchester-encoded data, 280kHz IF BW
+
Denotes a lead(Pb)-free/RoHs-compliant package.
**
EP = Exposed pad.
Note: The MAX7031 is available with factory-preset operating
frequencies. See the Selector Guide for complete part numbers.
Pin Configuration, Selector Guide, Typical Application
Circuit, and Functional Diagram appear at end of data sheet.
PART TEMP RANGE PIN-PACKAGE
MAX7031_ATJ__+ -40°C to +125°C 32 Thin QFN-EP**
MAX7031
Low-Cost, 308MHz, 315MHz, and 433.92MHz
FSK Transceiver with Fractional-N PLL
2 _______________________________________________________________________________________
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.
HVIN to GND .........................................................-0.3V to +6.0V
PAVDD, AVDD, DVDD to GND..............................-0.3V to +4.0V
ENABLE, T/R, DATA, AGC0, AGC1,
AUTOCAL to GND ...............................-0.3V to (V
HVIN
+ 0.3)V
All Other Pins to GND .............................-0.3V to (V
_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
Soldering Temperature (reflow) .......................................+260°C
DC ELECTRICAL CHARACTERISTICS
(
Typical Application Circuit
, 50Ω system impedance, V
PAV
DD
= V
AV
DD
= V
DV
DD
= V
HV
IN
= +2.1V to +3.6V, fRF= 308MHz, 315MHz, or
433.92MHz, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at V
PAV
DD
= V
AV
DD
= V
DV
DD
= V
HV
IN
= +2.7V,
T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage (3V Mode) V
Supply Voltage (5V Mode) V
Supply Current I
Voltage Regulator V
DIGITAL I/O
Input-High Threshold V
Input-Low Threshold V
Pulldown Sink Current
Output Low Voltage V
Output High Voltage V
DD
HVIN
HVIN, PAVDD, AVDD, and DVDD
connected to power supply
PAVDD, AVDD, and DVDD unconnected
from HVIN, but connected together
Transmit mode
(Note 2)
TA < +85°C,
typ at +25°C
DD
(Note 3)
TA < +125°C,
typ at +125°C
(Note 2)
REG
V
HVIN
(Note 2)
IH
(Note 2)
IL
AGC0-1, AUTOCAL, ENABLE, T/R, DATA
(V
OL
OH
I
SINK
I
SOURCE
fRF = 315MHz 11.6 19.1
f
= 434MHz 12.4 20.4
RF
Receiver 315MHz 6.4 8.4
Receiver 434MHz 6.7 8.7
Deep-sleep (3V mode) 0.8 8.8
Deep-sleep (5V mode) 2.4 10.9
Receiver 315MHz 6.8 8.7
Receiver 434MHz 7.0 8.8
Deep-sleep (3V mode) 8.0 34.2
Deep-sleep (5V mode) 14.9 39.3
HVIN
= 5V, I
= 5.5V)
= 15mA 3.0 V
LOAD
= 500µA 0.15 V
= 500µA
2.1 2.7 3.6 V
4.5 5.0 5.5 V
0.9 x
V
HVIN
0.1 x
V
HVIN
20 µA
V
HVIN
- 0.26
mA
µA
mA
µA
V
V
V
MAX7031
Low-Cost, 308MHz, 315MHz, and 433.92MHz
FSK Transceiver with Fractional-N PLL
_______________________________________________________________________________________ 3
AC ELECTRICAL CHARACTERISTICS
(
Typical Application Circuit
, 50Ω system impedance, V
PAV
DD
= V
AV
DD
= V
DV
DD
= V
HV
IN
= +2.1V to +3.6V, fRF= 308MHz, 315MHz. or
433.92MHz, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at V
PAV
DD
= V
AV
DD
= V
DV
DD
= V
HV
IN
= +2.7V,
T
A
= +25°C, unless otherwise noted.) (Note 1)
GENERAL CHARACTERISTICS
Frequency Range 308/315/433.92 MHz
Maximum Input Level P
Transmit Efficiency (Note 5)
Power-On Time t
RECEIVER
Sensitivity
Image Rejection 46 dB
POWER AMPLIFIER
Output Power P
Maximum Carrier Harmonics With output matching network -40 dBc
Reference Spur -50 dBc
PHASE-LOCKED LOOP
Transmit VCO Gain K
Transmit PLL Phase Noise
Receive VCO Gain 340 MHz/V
Receive PLL Phase Noise
Loop Bandwidth
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
RFIN
fRF = 315MHz 32
f
RF
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,
ON
OUT
VCO
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)
0.2% BER, 4kbps
Manchester data rate,
280kHz IF BW, FSK
±50kHz deviation
TA = +25°C (Note 3) 4.6 10.0 15.5
TA = +125°C, V
V
TA = -40°C, V
V
10kHz offset, 200kHz loop BW -68
1MHz offset, 200kHz loop BW -98
10kHz offset, 500kHz loop BW -80
1MHz offset, 500kHz loop BW -90
Transmit PLL 200
Receive PLL 500
= 434MHz 30
= +2.1V (Note 2)
HVIN
= +3.6V (Note 3)
HVIN
PAVDD
PAVDD
= V
315MHz -110
434MHz -107
= V
AVDD
= V
AVDD
= V
DVDD
DVDD
=
=
3.9 6.7
0 dBm
200
350
250
13.1 15.8
340 MHz/V
dBc/Hz
dBc/Hz
%
µs
dBm
dBm
kHz
MAX7031
Low-Cost, 308MHz, 315MHz, and 433.92MHz
FSK Transceiver with Fractional-N PLL
4 _______________________________________________________________________________________
AC ELECTRICAL CHARACTERISTICS (continued)
(
Typical Application Circuit
, 50Ω system impedance, V
PAV
DD
= V
AV
DD
= V
DV
DD
= V
HV
IN
= +2.1V to +3.6V, fRF= 308MHz, 315MHz. or
433.92MHz, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at V
PAV
DD
= V
AV
DD
= V
DV
DD
= V
HV
IN
= +2.7V,
T
A
= +25°C, unless otherwise noted.) (Note 1)
Reference Frequency Input Level 0.5 V
LOW-NOISE AMPLIFIER/MIXER (Note 7)
LNA Input Impedance Z
Voltage-Conversion Gain
Input-Referred 3rd-Order
Intercept Point
Mixer Output Impedance 330 Ω
LO Signal Feedthrough to
Antenna
RSSI
Input Impedance 330 Ω
Operating Frequency f
3dB Bandwidth 10 MHz
Gain 15 mV/dB
FSK DEMODULATOR
Conversion Gain 2.0 mV/kHz
ANALOG BASEBAND
Maximum Data Filter Bandwidth 50 kHz
Maximum Data Slicer Bandwidth 100 kHz
Maximum Peak Detector
Bandwidth
Maximum Data Rate
CRYSTAL OSCILLATOR
Crystal Frequency f
Frequency Pulling by V
Crystal Load Capacitance (Note 6) 4.5 pF
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
INLNA
IIP3
IF
XTAL
DD
Normalized to 50Ω
High-gain state
Low-gain state
High-gain state -42
Low-gain state -6
Manchester coded 33
Nonreturn to zero (NRZ) 66
fRF = 315MHz 1 - j4.7
= 434MHz 1 - j3.3
f
RF
fRF = 315MHz 50
= 434MHz 45
f
RF
fRF = 315MHz 13
= 434MHz 9
f
RF
-100 dBm
10.7 MHz
50 kHz
(fRF - 10.7)
/ 24
2 ppm/V
P-P
dB
dBm
kbps
MHz
MAX7031
Low-Cost, 308MHz, 315MHz, and 433.92MHz
FSK Transceiver with Fractional-N PLL
_______________________________________________________________________________________ 5
AC ELECTRICAL CHARACTERISTICS (continued)
(
Typical Application Circuit
, 50Ω system impedance, V
PAV
DD
= V
AV
DD
= V
DV
DD
= V
HV
IN
= +2.1V to +3.6V, fRF= 308MHz, 315MHz. or
433.92MHz, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at V
PAV
DD
= V
AV
DD
= V
DV
DD
= V
HV
IN
= +2.7V,
T
A
= +25°C, unless otherwise noted.) (Note 1)
Note 1: Supply current, output power, and efficiency are greatly dependent on board layout and PAOUT match.
Note 2: 100% tested at T
A
= +125°C. Guaranteed by design and characterization over temperature.
Note 3: Guaranteed by design and characterization. Not production tested.
Note 4: Time for final signal detection; does not include baseband filter settling.
Note 5: Efficiency = P
OUT
/(VDDx IDD).
Note 6: Dependent on PCB trace capacitance.
Note 7: 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.
Typical Operating Characteristics
(
Typical Operating Circuit
, V
PAVDD
= V
AVDD
= V
DVDD
= V
HVIN
= +3.0V, fRF= 433.92MHz, IF BW = 280kHz. 4kbps Manchester
encoded, 0.2% BER deviation = ±50kHz, TA= +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX7031 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
3.33.02.72.4
6.2
6.4
6.6
6.8
7.0
7.2
7.4
6.0
2.1 3.6
+85°C
+125°C
+25°C
-40°C
SUPPLY CURRENT vs. RF FREQUENCY
FSK MODE
MAX7030 toc02
RF FREQUENCY (MHz)
SUPPLY CURRENT (mA)
425400325 350 375
6.5
6.6
6.7
6.8
6.9
7.0
6.4
300 450
+85°C
+125°C
+25°C
-40°C
DEEP-SLEEP CURRENT vs. TEMPERATURE
MAX7031 toc03
TEMPERATURE (°C)
DEEP-SLEEP CURRENT (µA)
1108535 60-10-15
2
4
6
8
10
12
14
16
18
0
-40
VCC = +3.6V
VCC = +3.0V
VCC = +2.1V
MAX7031
Low-Cost, 308MHz, 315MHz, and 433.92MHz
FSK Transceiver with Fractional-N PLL
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(
Typical Operating Circuit
, V
PAVDD
= V
AVDD
= V
DVDD
= V
HVIN
= +3.0V, fRF= 433.92MHz, IF BW = 280kHz. 4kbps Manchester
encoded, 0.2% BER deviation = ±50kHz, T
A
= +25°C, unless otherwise noted.)
RECEIVER
BIT-ERROR RATE
vs. AVERAGE INPUT POWER
100
280kHz IF BW
10
1
BIT-ERROR RATE (%)
0.2% BER
0.1
fRF = 315MHz
0.01
-116 -104
AVERAGE INPUT POWER (dBm)
-108 -106-110-112-114
fRF = 434MHz
MAX7031 toc04
-100
-102
-104
-106
SENSITIVITY (dBm)
-108
-110
-112
SENSITIVITY vs. TEMPERATURE
280kHz IF BW
0.2% BER
-40
TEMPERATURE (°C)
fRF = 434MHz
fRF = 315MHz
SENSITIVITY vs. FREQUENCY DEVIATION
-94
MAX7031 toc05
11085603510-15
-96
-98
-100
-102
SENSITIVITY (dBm)
-104
-106
-108
1 100
FREQUENCY DEVIATION (kHz)
10
280kHz IF BW
0.2% BER
MAX7031 toc06
1.8
1.6
1.4
HIGH-GAIN MODE
1.2
1.0
RSSI (V)
0.8
0.6
0.4
0.2
AGC HYSTERESIS: 3dB
0
-130 10
RF INPUT POWER (dBm)
AGC SWITCH
POINT
LOW-GAIN MODE
MAX7031 toc07
-10-30-70 -50-90-110
SYSTEM GAIN vs. IF FREQUENCY
50
RSSI vs. RF INPUT POWER
40
30
20
10
SYSTEM GAIN (dBm)
0
-10
-20
45dB IMAGE
REJECTION
030
IF FREQUENCY (MHz)
UPPER SIDEBAND
FROM RFIN
TO MIXOUT
= 434MHz
f
RF
LOWER SIDEBAND
252015105
MAX7031 toc10
RSSI AND DELTA vs. IF INPUT POWER
2.1
1.8
1.5
1.2
RSSI (V)
0.9
0.6
0.3
0
-90 10
IMAGE REJECTION vs. TEMPERATURE
48
46
44
IMAGE REJECTION (dB)
42
-40
RSSI
IF INPUT POWER (dBm)
fRF = 315MHz
TEMPERATURE (°C)
MAX7031 toc08
DELTA
-10-30-50-70
fRF = 434MHz
11085603510-15
3.5
2.5
1.5
0.5
-0.5
-1.5
-2.5
-3.5
MAX7031 toc11
1.6
1.2
0.8
DELTA (%)
0.4
FSK DEMODULATOR OUTPUT (V)
0
10.4 11.0
NORMALIZED IF GAIN vs. IF FREQUENCY
0
-4
-8
-12
NORMALIZED IF GAIN (dB)
-16
-20
1 100
FSK DEMODULATOR OUTPUT
vs. IF FREQUENCY
MAX7031 toc09
10.910.810.710.610.5
IF FREQUENCY (MHz)
MAX7031 toc12
10
IF FREQUENCY (MHz)