th71112 Melexis Company, th71112 Datasheet - Page 3

• Manufacturer Part Number: th71112
• Description: Receiver - 868/915mhz Fsk/ask, Double-conversion Superhet Lqfp32
• Manufacturer: Melexis Company

1
1.1
With the TH71112 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.
The superheterodyne configuration is double conversion where MIX1 and MIX2 are driven by the internal
local oscillator signals LO1 and LO2, respectively. This allows a high degree of image rejection, achieved in
conjunction with an RF front-end filter. 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.
A single-conversion variant, called TH71111, is also available. Both Receiver ICs have the same die. At the
TH71111 the second mixer MIX2 operates as an amplifier.
The TH71112 receiver IC consists of the following building blocks:
1.2
1) at 4 kbps NRZ, BER = 3⋅10
2) at 4 kbps NRZ, BER = 3⋅10
39010 71112
Rev. 014
PLL synthesizer (PLL SYNTH) for generation of the first and second local oscillator signals LO1 and
LO2, parts of the PLL SYNTH are: the high-frequency VCO1, the feedback dividers DIV_16 and DIV_2,
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 first IF (IF1)
Second mixer (MIX2) for down-conversion of the IF1 to the second IF (IF2)
IF amplifier (IFA) to amplify and limit the IF2 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
Input frequency range: 750 MHz to 990 MHz
Power supply range: 2.3 V to 5.5 V @ ASK
Temperature range: -40 °C to +85 °C
Standby current: 50 nA
Operating current: 7.5 mA @ low gain mode
Sensitivity: -112 dBm @ ASK 1)
Maximum data rate: 260 kbps NRZ @ ASK
Range of IF1: 10 MHz to 80 MHz
Theory of Operation
General
Technical Data Overview
-106 dBm @ FSK 2)
9.2 mA @ high gain mode
180 kbps NRZ @ FSK
-3
-3
, ± 20 kHz FSK deviation, 180 kHz IF filter BW, without SAW front-end-filter loss
, 180 kHz IF filter BW, without SAW front-end-filter loss
Page 3 of 22
Range of IF2: 400 kHz to 22 MHz
Maximum input level: -10 dBm @ ASK
Image rejection: > 60 dB (e.g. with 868.3 MHz
SAW front-end filter and at 10.7 MHz IF2)
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
FSK/ASK Receiver
0 dBm @ FSK
TH71112
868/915MHz
Data Sheet
April/08