th71221 Melexis Company, th71221 Datasheet - Page 4

• Manufacturer Part Number: th71221
• Description: Transceiver - 27 To 930mhz, Fsk/fm/ask, Multi-channel 32l Qfn 5x5 Quad
• Manufacturer: Melexis Company

1
1.1
The main building block of the transceiver is a programmable PLL frequency synthesizer that is based on an
integer-N topology. The PLL is used for generating the carrier frequency during transmission and for
generating the LO signal during reception. The carrier frequency can be FSK-modulated either by pulling the
crystal or by modulating the VCO directly. ASK modulation is done by on/off keying of the power amplifier.
The receiver is based on the principle of a single conversion superhet. Therefore the VCO frequency has to
be changed between transmit and receive mode. In receive mode, the default LO injection type is low-side
injection.
The TH71221 transceiver IC consists of the following building blocks:
1.2
1.3 Note on ASK Operation
Optimum ASK performance can be achieved by using an 8-MHz crystal for operation at 315 MHz, 434 MHz
and 915 MHz. For details please refer to the software settings shown in sections 7.4 and 7.6. FSK operation
is the preferred choice for applications in the European 868MHz band.
39010 071221
Rev. 006
Low-noise amplifier (LNA) for high-sensitivity
RF signal reception with switchable gain
Mixer (MIX) for RF-to-IF down-conversion
IF amplifier (IFA) to amplify and limit the IF
signal and for RSSI generation
Phase-coincidence FSK demodulator with
external ceramic discriminator or LC tank
Operational amplifier (OA1), connected to
demodulator output
Operational amplifier (OA2), for general use
Peak detector (PKDET) for ASK detection
Frequency range: 300 MHz to 930 MHz in
programmable user mode
Extended frequency range with external VCO
varactor diode: 27 MHz to 930 MHz
315 MHz, 433 MHz, 868 MHz or 915 MHz fixed-
frequency settings in stand-alone mode
Power supply range: 2.2 V to 5.5 V
Temperature range: -40 °C to +85 °C
Standby current: 50 nA
Operating current in receive: 6.5 mA (low gain)
Operating current in transmit: 12 mA (at -2 dBm)
Adjustable RF power range: -20 dBm to +10dBm
Sensitivity: -105 dBm at FSK with 180 kHz
IF filter BW
Theory of Operation
General
Technical Data Overview
Page 4 of 44
Control logic with 3wire bus serial control
interface (SCI)
Reference oscillator (RO) with external crystal
Reference divider (R counter)
Programmable divider (N/A counter)
Phase-frequency detector (PFD)
Charge pump (CP)
Voltage controlled oscillator (VCO) with internal
varactor
Power amplifier (PA) with adjustable output
power
Sensitivity: -107 dBm at ASK with 180 kHz
IF filter BW
Max. data rate with crystal pulling: 20 kbps NRZ
Max. data rate with direct VCO modulation:
115 kbps NRZ
Max. input level: -10 dBm at FSK
and -20 dBm at ASK
Input frequency acceptance: ± 10 to ± 150 kHz
(depending on FSK deviation)
FM/FSK deviation range: ±2.5 to ±80 kHz
Analog modulation frequency: max. 10 kHz
Crystal reference frequency: 3 MHz to 12 MHz
External reference frequency: 1 MHz to 16 MHz
FSK/FM/ASK Transceiver
TH71221
27 to 930MHz
Data Sheet
June/08