Chapter 2 Theory Of Operation; Introduction; Radio Power Distribution; Figure 2-1. Dc Power Distribution Block Diagram - Motorola PR860 Detailed 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 4-56.
2.2

Radio Power Distribution

A block diagram of the DC power distribution throughout the radio board is shown in
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
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
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)
Figure 2-1
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

and described in
Int/Ext Vdd
Vdda Vdda
Vdda
Vddd
MCU, ROM LCD
Tx
and EEPROM Driver
Led
5V
Regulator
5V
RF, AMP, IF AMP
Table 2-1 on page
Table 2-2 on page 2-2.
Accessories
20 pin Connector
Keypad/Option Board
Prime Expansion Board
Switching
Regulator
FRACTN
ASFIC_CMP
VCOBIC
Ext. RX.
Buffer (NU)
2-1
Figure 2-1. A
2-2. Data is then
LVZIF