General Description

The MAX7031 crystal-based, fractional-N transceiver is

designed to transmit and receive FSK data at factory-

preset carrier frequencies of 308MHz

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 50

Ω

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.

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

Low-Cost, 308MHz, 315MHz, and 433.92MHz

FSK Transceiver with Fractional-N PLL

________________________________________________________________

Maxim Integrated Products

1

Ordering Information

19-3707; Rev 2; 6/09

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.

PART

TEMP RANGE

PIN-PACKAGE

MAX7031_ATJ__+

-40°C to +125°C

32 Thin QFN-EP**

*

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 num-

bers.

Pin Configuration, Selector Guide, Typical Application

Circuit, and Functional Diagram appear at end of data sheet.