Datasheet TH7122 (Melexis) - 4

TH7122 27 to 930MHz FSK/FM/ASK Transceiver 1 Theory of Operation 1.1 General
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: " Low-noise amplifier (LNA) for high-sensitivity " Control logic with 3wire bus serial control RF signal reception with switchable gain interface (SCI) " Mixer (MIX) for RF-to-IF down-conversion " Reference oscillator (RO) with external crystal " IF amplifier (IFA) to amplify and limit the IF " Reference divider (R counter) signal and for RSSI generation " Programmable divider (N/A counter) " Phase-coincidence FSK demodulator with " Phase-frequency detector (PFD) external ceramic discriminator or LC tank " Charge pump (CP) " Operational amplifier (OA1), connected to " Voltage controlled oscillator (VCO) with internal demodulator output varactor " Operational amplifier (OA2), for general use " Power amplifier (PA) with adjustable output " Peak detector (PKDET) for ASK detection power
1.2 Technical Data Overview
! Frequency range: 300 MHz to 930 MHz in ! Sensitivity: -107 dBm at ASK with 180 kHz programmable user mode IF filter BW ! Extended frequency range with external VCO ! Max. data rate with crystal pulling: 20 kbps NRZ varactor diode: 27 MHz to 930 MHz ! Max. data rate with direct VCO modulation: ! 315 MHz, 433 MHz, 868 MHz or 915 MHz fixed- 115 kbps NRZ frequency settings in stand-alone mode ! Max. input level: -10 dBm at FSK ! Power supply range: 2.2 V to 5.5 V and -20 dBm at ASK ! Temperature range: -40 °C to +85 °C ! Input frequency acceptance: ± 10 to ± 150 kHz ! Standby current: 50 nA (depending on FSK deviation) ! Operating current in receive: 6.5 mA (low gain) ! FM/FSK deviation range: ±2.5 to ±80 kHz ! Operating current in transmit: 12 mA (at -2 dBm) ! Analog modulation frequency: max. 10 kHz ! Adjustable RF power range: -20 dBm to +10dBm ! Crystal reference frequency: 3 MHz to 12 MHz ! Sensitivity: -105 dBm at FSK with 180 kHz ! External reference frequency: 1 MHz to 16 MHz IF filter BW
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 Page 4 of 44 Data Sheet Rev. 008 June/07 Document Outline Features Ordering Information Application Examples Pin Description General Description Document Content 1 Theory of Operation 1.1 General 1.2 Technical Data Overview 1.3 Note on ASK Operation 1.4 Block Diagram 1.5 User Mode Features 2 Pin Definitions and Descriptions 3 Functional Description 3.1 PLL Frequency Synthesizer 3.1.1 Reference Oscillator (XOSC) 3.1.2 Reference Divider 3.1.3 Feedback Divider 3.1.4 Frequency Resolution and Operating Frequency 3.1.5 Phase-Frequency Detector 3.1.6 Lock Detector 3.1.7 Voltage Controlled Oscillator with external Loop Filter 3.1.8 Loop Filter Receiver Part 3.2.1 LNA 3.2.2 Mixer 3.2.3 IF Amplifier 3.2.4 ASK Demodulator 3.2.5 FSK Demodulator 3.3 Transmitter Part 3.3.1 Power Amplifier Output Power Adjustment 3.3.3 Modulation Schemes 3.3.4 ASK Modulation 3.3.5 FSK Modulation 3.3.6 Crystal Tuning 4 Description of User Modes 4.1 Stand-alone User Mode Operation 4.1.1 Frequency Selection 4.1.2 Operation Mode 4.1.3 Modulation Type 4.1.4 LNA Gain Mode 4.2 Programmable User Mode Operation 4.2.1 Serial Control Interface Description 5 Register Description 5.1 Register Overview 5.1.1 Default Register Settings for FS0, FS1 5.1.2 A – word 5.1.3 B – word 5.1.4 C – word 5.1.5 D – word 6 Technical Data 6.1 Absolute Maximum Ratings 6.2 Normal Operating Conditions 6.3 DC Characteristics 6.4 PLL Synthesizer Timings 6.5 AC Characteristics of the Receiver Part 6.6 AC Characteristics of the Transmitter Part 6.7 Serial Control Interface 6.8 Crystal Parameters 7 Application Circuit Examples 7.1 FSK Application Circuit Programmable User Mode (internal AFC option) 7.2 FSK Application Circuit Stand-alone User Mode 7.3 FSK Test Circuit Component List (Fig. 14 and Fig. 15) 7.4 ASK Application Circuit Programmable User Mode (normal data slicer option) 7.5 ASK Test Circuit Component List (Fig. 16) 7.6 ASK Application Circuit Programmable User Mode (peak detector option) 7.7 ASK Test Circuit Component List (Fig. 17) 8 Extended Frequency Range 8.1 Board Component List (Fig. 18) 9 TX/RX Combining Network 9.1 Board Component List (Fig. 19) 9.2 Typical LNA S-Parameters in Receive Mode 9.3 LNA Input Impedances in Transmit Mode 10 Package Description 10.1 Soldering Information 11 Reliability Information 12 ESD Precautions Your Notes 13 Disclaimer