Rainbow Electronics MAX7057 User Manual

General description, Applications, Features

General Description

The MAX7057 frequency-programmable UHF transmit-
ter is designed to transmit ASK/FSK data at a wide
range of frequencies from 300MHz to 450MHz. The
MAX7057 has internal tuning capacitors at the output of
the power amplifier that are programmable for match-
ing to an antenna or load. This allows the user to
change to a new frequency and match the antenna at
the new frequency simultaneously. The MAX7057 trans-
mits at a data rate up to 100kbps nonreturn-to-zero
(NRZ) (50kbps Manchester coded). Typical transmitted
power into a 50Ω load is +9.2dBm with a +2.7V supply.
The device operates from +2.1V to +3.6V and typically
draws under 12.5mA of current in FSK mode (8.5mA in
ASK mode) when the antenna-matching network is
designed to operate over the 315MHz to 433.92MHz
frequency range. For narrower operating frequency
ranges, the matching network can be redesigned to
improve efficiency. The standby current is less than
1μA at room temperature.

The MAX7057 reference frequency from the crystal
oscillator is multiplied by a fully integrated fractional-N
phase-locked loop (PLL). The multiplying factor of the
PLL is set by a 16-bit number, with 4 bits for integer
and 12 bits for fraction; the multiplying factor can be
anywhere between 19 and 28. The 12-bit fraction in the
synthesizer sets a tuning resolution equal to the refer-
ence frequency divided by 4096; frequency deviation
can be set as low as ±2kHz and as high as ±100kHz.
The fractional-N synthesizer eliminates the problems
associated with oscillator-pulling FSK signal generation.
The MAX7057 has a serial peripheral interface (SPI™)
for selecting all the necessary settings.

The MAX7057 is available in a 16-pin SO package and
is specified to operate in the -40°C to +125°C automo-
tive temperature range.

Applications

RF Remote Controls

Garage Door Openers

Home Automation

Automotive

Wireless Sensors

Wireless Game Consoles

Wireless Computer Peripherals

Security Systems

Features

♦ Programmable Frequency Operation with Single

Crystal

♦ Internal Variable Capacitor for Antenna Tuning

with Single-Matching Network

♦ 100kbps Data Rate (NRZ)
♦ +2.1V to +3.6V Single-Supply Operation
♦ < 12.5mA (FSK), < 8.5mA (ASK) DC Current Drain
♦ < 1µA Standby Current
♦ ASK/FSK Modulation
♦ 47% Carrier Tuning Range Using One Crystal

MAX7057

300MHz to 450MHz Frequency-Programmable

ASK/FSK Transmitter

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Maxim Integrated Products

Pin Configuration

Ordering Information

19-4093; Rev 0; 5/08

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.

Denotes a lead-free package.

PART

TEMP RANGE

PIN-PACKAGE

MAX7057ASE+

-40°C to +125°C

16 SO

Typical Application Circuit and Functional Diagram appear
at end of data sheet.

SPI is a trademark of Motorola, Inc.

DGND

DIN

PAGND

DVDD

GPO

SDI

SCLK

TOP VIEW

AGND

XTAL1

XTAL2

PAVDD

AVDD

ENABLE

PAOUT

ROUT 6

MAX7057