th7122 Melexis Company, th7122 Datasheet - Page 4

• Manufacturer Part Number: th7122
• Description: Transceiver - 27 To 930mhz, Fsk/fm/ask, Multi-channel Lqfp32
• 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 TH7122 transceiver IC consists of the following building blocks:
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1.2
! Frequency range: 300 MHz to 930 MHz in
! Extended frequency range with external VCO
! 315 MHz, 433 MHz, 868 MHz or 915 MHz fixed-
! 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
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 07122
Rev. 008
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
programmable user mode
varactor diode: 27 MHz to 930 MHz
frequency settings in stand-alone mode
IF filter BW
Theory of Operation
General
Technical Data Overview
Page 4 of 44
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! Sensitivity: -107 dBm at ASK with 180 kHz
! Max. data rate with crystal pulling: 20 kbps NRZ
! Max. data rate with direct VCO modulation:
! Max. input level: -10 dBm at FSK
! Input frequency acceptance: ± 10 to ± 150 kHz
! 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
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
IF filter BW
115 kbps NRZ
and -20 dBm at ASK
(depending on FSK deviation)
FSK/FM/ASK Transceiver
27 to 930MHz
TH7122
Data Sheet
June/07