TH71112 Datasheet, PDF (2/20 Pages) List of Unclassifed Manufacturers – 868/915MHz FSK/FM/ASK Receiver

TH71112
868/915MHz
FSK/FM/ASK Receiver
General Description
The TH71112 receiver IC consists of the following building blocks:
" 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 IF1
" second mixer (MIX2) for down-conversion of the IF1 to the second IF (IF2)
" 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
With the TH71112 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
FM / FSK
FM / FSK
ASK
Type of receiver
narrow-band RX with ceramic demodulation tank
wide-band RX with LC demodulation tank
RX with RSSI-based demodulation
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 frontend filter. 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.
A single-conversion variant, called TH71111, is also available. Both RXICs have the same die. At the
TH71111 the second mixer MIX2 operates as an amplifier.
TH71112 Data Sheet
3901071112
Page 2 of 20
Nov. 2001
Rev. 005