TH71101_13 Datasheet, PDF (3/20 Pages) Melexis Microelectronic Systems – FSK/ASK Receiver

TH71101
315/433MHz
FSK/ASK Receiver
1 Theory of Operation
1.1 General
With the TH71101 receiver chip, various circuit configurations can be arranged in order to meet a number of
different customer requirements. For FSK reception the IF tank used in the phase coincidence demodulator
can be constituted by an external ceramic discriminator. In ASK configuration, the RSSI signal is fed to an
ASK detector, which is constituted by the operational amplifier.
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 front-end 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 front-end 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.
The TH71101 receiver IC consists of the following building blocks:
PLL synthesizer (PLL SYNTH) for generation of the local oscillator signal LO, 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)
Low-noise amplifier (LNA) for high-sensitivity RF signal reception
First mixer (MIX1) for down-conversion of the RF signal to the IF
IF pre amplifier which is a mixer cell (MIX2) that operates as an amplifier
IF amplifier (IFA) to amplify and limit the IF signal and for RSSI generation
Phase coincidence demodulator (DEMOD) with third mixer (MIX3) to demodulate the IF signal
Operational amplifier (OA) for data slicing, filtering and ASK detection
Bias circuitry for bandgap biasing and circuit shutdown
1.2 Technical Data Overview
Input frequency range: 300to 450 MHz
Power supply range: 2.3 to 5.5 V @ ASK
Temperature range: -40 to +85 °C
Standby current:
50 nA
Operating current:
6.5 mA @ low gain
8.2 mA @ high gain
Sensitivity:
-113 dBm @ ASK 1)
-107 dBm @ FSK 2)
Maximum data rate: 260 kbps NRZ @ ASK
180 kbps NRZ @ FSK
Range of IF:
400 kHz to 22 MHz
Maximum input level: -10 dBm @ ASK
0 dBm @ FSK
Image rejection:
> 45 dB (e.g. with 433.92
MHz SAW front-end filter and at 10.7 MHz IF)
Spurious emission: < -70 dBm
Input frequency acceptance range: up to ±100 kHz
RSSI range: 70 dB
FSK deviation range: ±2.5 kHz to ±80 kHz
1) at 4 kbps NRZ, BER = 3⋅10^-3, 180 kHz IF filter BW, without SAW front-end-filter loss
2) at 4 kbps NRZ, BER = 3⋅10^-3, ± 20 kHz FSK deviation, 180 kHz IF filter BW, without SAW front-end-filter
loss
39010 71101
Rev. 018
Page 3 of 21
Data Sheet
Jun/13