EVB7122 Melexis Company, EVB7122 Datasheet - Page 3

• Manufacturer Part Number: EVB7122
• Description: Evaluation Board For Th7122 And Th71221
• 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 by pulling the
crystal and ASK-modulated 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 preferred LO injection type is low-side injection.
The TH7122 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 4.2 and 4.3. FSK operation
is the preferred choice for applications in the European 868MHz band.
39012 07122 02
Rev. 006
RF signal reception with switchable gain
signal and for RSSI generation
ceramic discriminator (FSK Demodulator)
demodulator output
Low-noise amplifier (LNA) for high-sensitivity
Mixer (MIX) for RF-to-IF down-conversion
IF amplifier (IFA) to amplify and limit the IF
Phase-coincidence demodulator with external
Operational amplifier (OA1), connected to
Operational amplifier (OA2), for geral 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
For more detailed information, please refer to the latest TH7122 data sheet revision
Page 3 of 24
interface (SCI)
varactor
power
Control logic with 3wire bus serial control
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
Power amplifier (PA) with adjustable output
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
Evaluation Board Description
27 to 930MHz Transceiver
EVB7122
EVB Description
June/08