TH71101

315/433MHz

FSK/FM/ASK Receiver

TH71101 Data Sheet

Page 2 of 20

Nov. 2001

3901071101

Rev. 005

General Description

The TH71101 receiver IC consists of the following building blocks

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PLL synthesizer (PLL SYNTH) for generation of the local oscillator signal LO

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Parts of the PLL SYNTH are the high-frequency VCO1, the feedback divider DIV_16,

a phase-frequency detector (PFD) with charge pump (CP) and a crystal-based reference oscillator (RO)

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Low-noise amplifier (LNA) for high-sensitivity RF signal reception

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First mixer (MIX1) for down-conversion of the RF signal to the IF

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IF pre amplifier which is a mixer cell (MIX2) that operates as an amplifier

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IF amplifier (IFA) to amplify and limit the IF signal and for RSSI generation

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Phase coincidence demodulator (DEMOD) with third mixer (MIX3) to demodulate the IF signal

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Operational amplifier (OA) for data slicing, filtering and ASK detection

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Bias circuitry for bandgap biasing and circuit shutdown

With the TH71101 receiver chip, various circuit configurations can be arranged in order to meet a number of

different customer requirements. For FM/FSK reception the IF tank used in the phase coincidence demodu-

lator can be constituted either by a ceramic resonator or an LC tank (optionally with a varactor diode to create

an AFC circuit). In ASK configuration, the RSSI signal is feed to an ASK detector, which is constituted by the

operational amplifier.

Demodulation

Type of receiver

FM / FSK

narrow-band RX with ceramic demodulation tank

FM / FSK

wide-band RX with LC demodulation tank

ASK

RX with RSSI-based demodulation

A double-conversion variant, called TH71102, is also available. This receiver IC allows a higher degree of

image rejection, achieved in conjunction with an RF frontend filter. Both RXICs have the same die. At the

TH71102, the second mixer (MIX2) is used to down-convert the first IF (IF1) to the second IF (IF2). At the

TH71101, MIX2 operates as an amplifier.

Efficient RF frontend filtering is realized by using a SAW, ceramic or helix filter in front of the LNA and by

adding an LC filter at the LNA output.