ATA5745 datasheet(2/43 Pages) ATMEL

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4596A–RKE–05/06

ATA5745/ATA5746 [Preliminary]

General Description

The ATA5745/ATA5746 is a UHF ASK/FSK transparent receiver IC with low power consumption

supplied in a small QFN24 package (body 5 mm

× 5 mm, pitch 0.65 mm). ATA5745 is used in

the 433 MHz to 435 MHz band of operation, and ATA5746 in 313 MHz to 317 MHz. The IC com-

bines the functionality of remote keyless entry (RKE - typically low bit rate ASK) and tire

pressure monitoring (TPM - typically high bit rate FSK) into one receiver under the control of an

external microcontroller such as an ATmega48 (AVR®).

For improved image rejection and selectivity, the IF frequency is fixed to 440 kHz. The IF block

uses an 8th-order band pass yielding a receive bandwidth of 420 kHz. This enables the use of

the receiver in both SAW- and PLL-based transmitter systems utilizing various types of data-bit

encoding such as pulse width modulation, Manchester modulation, variable pulse modulation,

pulse position modulation, and NRZ. Prevailing encryption protocols such as Keeloq

® are easily

supported due to the receiver’s ability to hold the current data slicer threshold for up to 52 ms

when incoming RF telegrams contain a blanking interval. This feature eliminates erroneous

noise from appearing on the demodulated data output pin, and simplifies software decoding

algorithms. The decoding of the data stream must be carried out by a connected microcontroller

device. Because of the highly integrated design, the only required RF components are for the

purpose of receiver antenna matching.

ATA5745 and ATA5746 support Manchester bit rates of 1 Kbit/s to 10 Kbits/s in ASK and 1 Kbit/s

to 20 Kbits/s in FSK mode. The four discrete bit rate passbands are selectable and cover

1.0 Kbit/s to 2.5 Kbits/s, 2.0 Kbits/s to 5.0 Kbits/s, 4.0 Kbits/s to 10.0 Kbits/s, and 8.0 Kbits/s to

10.0 Kbits/s or 20.0 Kbits/s (for ASK or FSK, respectively). The receiver contains an RSSI output

to provide an indication of received signal strength and a SENSE input to allow the customer to

select a threshold below which the DATA signal is gated off. ASK/FSK and bit rate ranges are

selected by the connected microcontroller device via pins ASK_NFSK, BR0, and BR1.

Figure 1-1.

System Block Diagram

(LNA, Mixer,

VCO, PLL,

IF Filter,

RSSI Amp.,

Demodulator)

RF Receiver

ATA5745/ATA5746

Antenna

XTO

Microcontroller

Interface

4 ... 8

Power

Supply

Digital Control

Logic

ATA5745 Datasheet(PDF) 2 Page - ATMEL Corporation

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