After Sales Technical Documentation THX–4 Series Transceiver Chapter 4 SYSTEM MODULE Original, 09/94
THX–4 System Module After Sales Technical Documentation CHAPTER 4 – SYSTEM MODULE CONTENTS Page No Introduction 4–5 General 4–5 Special Features 4–5 Technical Specifications 4–5 Modes of Operation 4–5 External Signals and Connections 4–5 System Connector J1 4–6 Display Module Connector J2 4–7 Internal Signals Connections between RF and Baseband Functional Description Logic Circuit Description 4–8 4–8 4–9 4–9 General 4–9 Micro–controller 4–9 Micro–controller D404 Pinout 4–9 Modem 4
After Sales Technical Documentation THX–4 System Module Transmitter 4–16 Duplexer and Spurious Rejection 4–17 List of Figures Version 6 Figure 1: Component Layout Diagram (Top Side) – Sheet 1 4–19 Figure 2: Component Layout Diagram (Top Side) – Sheet 2 4–20 Figure 3: Component Layout Diagram (Bottom Side) – Sheet 1 4–21 Figure 4: Component Layout Diagram (Bottom Side) – Sheet 2 4–22 Figure 5: RF Circuit Diagram (A2) 4–23 Figure 6: Baseband Circuit Diagram (A2) 4–24 Figure 7: Keyboard Circu
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After Sales THX–4 Technical Documentation System Module Introduction General The system module controls the operation of the internal parts of the phone. Its task is to control the user interface, i.e. LCD driver, keyboard, and audio interface functions. The module performs all signalling towards the system and carries out audio–frequency signal processing. In addition, it controls the operation of the transceiver and stores tuning data for the phone.
After Sales THX–4 Technical Documentation System Module System Connector J1 Page 4–6 Pin Name Description 1 VC Charger Input +ve 2 XEXAUD Booster power control output. 3 HOOK On hook indication for auxillary handset. 4 XEAR External earphone signal. 5 0V 0V for both charger and audio. 6 VC Charger input +ve 7 MBUS Bidirectional asynchronous data bus.
After Sales THX–4 Technical Documentation System Module Display Module Connector J2 Pin Name Description 1 ROW1 Row 1 of keypad matrix 2 COL0 Column 0 of keypad matrix 3 ROW0 Row 0 of keypad matrix 4 COL3 Column 3 of keypad matrix 5 VBAT Battery voltage power for LED’s 6 Current supply for LCD backlights 7 LCD LIGHTS LCD_CLK 8 LCD_RES Reset for LCD driver 9 XLCDEN LCD driver for chip enable 10 C_XD Command/No data 11 SCL Serial data clock 12 VL2 Supply voltage for LCD
After Sales THX–4 Technical Documentation System Module Internal Signals Connections between RF and Baseband Page 4–8 Name Function DAF RX audio and data IF_FREQ 2nd IF input VTCXO VTCXO control signal RSSI Received signal strength indicator V_REF Voltage regulator reference, 4.
After Sales THX–4 Technical Documentation System Module Functional Description Logic Circuit Description General The audio/logic unit consists of 5 IC’s: controller D404, modem N403, audio NANTIC N408, EEPROM D406, regulator PSL N407. Micro–controller Micro–controller D404 has six 8–bit I/O ports (Ports 1, 3, 4, 5, 7 and 9), one 5–bit port (Port 2), one 4–bit I/O port (Port 6) an 10–bit 8–channel A/D converter (Port 8), three PWM timers, serial communication interface.
After Sales THX–4 Technical Documentation System Module Pin Name Description 30–36 ROW 0–6 Keypad inputs 37 OUT_T Buzzer Volume Control 38 COL 0 Keypad outputs and power up control 39–41 COL 1–3 Keypad outputs 42 VCC2 Logic Supply Voltage VL1 Input 43 SYNDAT Serial data for RF synthesizers 44 LIGHTS Output to turn ’on’ the LED’s 45 RXLE Latch enable for RX synthesizer 46 MBUSNF MBUS input 47 TXLE Latch enable for the TX synthesizer 48 5VRXEN RX RF supply switch control
After Sales THX–4 Technical Documentation System Module Pin Name Description 72 ACLK Clock for NANTIC 73 XBUSY Busy signal for LCD driver 74 XLCDEN LCD driver IC select 75 C_XD LCD driver and EEPROM multiplex control 76 CSCK NANTIC and SIS serial interface clock 77 SYNCLK Synthesiser serial data clock 78 NMI Modem interrupt 79 SDA Serial data to EEPROM and LCD–driver 80 XAS Address bit for Modem Modem The NAT (N403) is a single VLSI chip modem for the AMPS/TACS mobile telep
After Sales THX–4 System Module Technical Documentation PSL N407 Signals Name Description VBAT battery voltage input VREF VA voltage reference output (+4.85V 2 %) logic voltage output (+4.85 V) for controller logic voltage output (+4.85 V) for other logic analogue voltage output (+4.
After Sales Technical Documentation THX–4 System Module Charging Control The circuit is basically a power switch, V403, which connects an external constant current source to the battery. V403 is driven by a modified long tail pair (emitter–coupled pair) which provides a safety mechanism to stop excessive voltages being placed across the phone’s internal circuitry.
After Sales THX–4 Technical Documentation System Module Name Description MICAMP MUX Signal from the microphone is fed to this stage and amplified TX source selection (EXMIC/MIC/DTMF/MUTED) TXAAFIL Anti alias filter (see NANTIC specification) BANDPASS (see NANTIC specification) TXATT For handsfree mode of operation COMPRESSOR 2:1 syllabic compressor PREEMP Pre–emphasis filter AGC Soft Limiter LIMU Hard limiter LOWPASS Low pass notch filter POSTFIL Second order Sallen–Key filter SUMS
After Sales Technical Documentation THX–4 System Module RF Circuit Description Receiver Signal Path The receiver is a dual–conversion superheterodyne with the intermediate frequencies 45 MHz and 450 kHz. The RF signal from the Antenna is first filtered from the Transmitter Signal by the Duplex Filter. It is then applied to V1 the Low Noise Amplifier (LNA). This amplifies the signal to a level sufficiently high to overcome the conversion noise of the First Mixer N8.
After Sales THX–4 System Module Technical Documentation Received Signal Strength Indicator (RSSI) is derived internally in N1 and is fed directly to one channel of the ADC input on D404. Synthesizers Both the Transmitter (N2 and N4) and Receiver (N7 and N12) Synthesizers are dual modulus types with VCO’s operating at final frequency. In the case of the Receiver the LO operates at Frx + 45MHz and in the Transmitter the VCO operates directly at the TX frequency.
After Sales Technical Documentation THX–4 System Module The final two stages of the PA use Gallium Arsenide (GaAs) technology to maximise efficiency. Because of the ’spread ’ inherent in GaAs devices, provision has been made to trim the DC bias point of both the driver and PA stages using discrete DACs based around V413 and V415 driven from the port of D404. Microstrip components are used to form low loss matching networks.
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