Theory Of Operation; Introduction; Radio Power Distribution; Figure 2-1:Dc Power Distribution Block Diagram - Motorola Professional Radio Service Manual

Chapter 2

Theory of Operation

2.1

Introduction

This chapter provides a detailed theory of operation for the radio components. Schematic diagrams
for the circuits described in the following paragraphs are located in Figures 4-1 through 4-120.
2.2

Radio Power Distribution

A block diagram of the DC power distribution throughout the radio board is shown in Figure 2-1. A
7.5V battery supplies the basic radio power (UNSWB) directly to the electronic on/off control, audio
power amplifier, 3.5V regulator, power amplifier automatic level control (ALC), and low battery detect
circuit. When the radio on/off/volume control is turned on, the switched SWB+ is applied to the various
radio power regulators, antenna switch, accessories 20-pin connector, keypad/option board, and
transmit LED. The Vdda signal from the 3.3V Vdda regulator supplies the microprocessor with
operating power. The Vdd regulator scheme is listed by band in Table 2-1. Data is then sent to the
controller ASFIC to turn on a DAC which takes over the momentary-on path within 12ms. The SWB+
signal supplies power until the radio is turned off. Jumpers for configuring the Vdda and Vddd
regulators are shown in Figure 2-1 and described in Table 2-2.
The radio turns off when either of the two following conditions occur:
• Radio on/off/volume control is turned off.
• Low battery condition is detected.
If a low battery level is detected by the microprocessor through either of the above conditions, the
radio personality data is stored to EEPROM prior to turning off.
UNSWB+
7.5V
Battery
Fuse
MECH.
SWB+
3.5V
Reg.
LI Ion
PA, Driver
PCIC(ALC)
Audio
Power
Amplifier
4.0V/3.3V
Regulator
SWB+
Regulator
Control
On/Off
Switch
Low Battery
Detect
Antenna
Switch
Figure 2-1: DC Power Distribution Block Diagram
Int/Ext Vdd
Vdda
Vdda
Vddd Vdda
MCU, ROM
Tx LCD
and EEPROM Driver
Led
5V
Regulator
5V
RF, AMP, IF AMP
Accessories
20 pin Connector
Keypad/Option Board
Prime Expansion Board
Switching
Regulator
FRACTN
ASFIC_CMP
VCOBIC
Ext. RX.
Buffer (NU)
2-1
LVZIF