Motorola GP series, Detailed Service Manual

Page: 63 / 494

Chapter 1
THEORY OF OPERATION
1.0 Overview
This Chapter provides a detailed theory of operation for the power distribution and controller circuits
in the radio. The components for these circuits are contained on the Main Board. Refer to the RF
sections of this manual for the component location details and the parts lists for these circuits.
2.0 Radio Power Distribution
Figure 1-1 illustrates the DC distribution throughout the radio board. A 7.5V battery (BATT 7.5V)
supplies power directly to the electronic on/off control as UNSWB+. When the radio is turned on,
M (on/off/volume control) will trigger the electronic on/off control (momentary-on path),
then SWB+ is distributed as shown in Figure1-1. Vdda from 3.3V Vdda regulator will then supply the
microprocessor. Data is then sent to ASFIC_CMP to turn on GCB4(DAC). GCB4 will take over the
momentary-on path within 12ms. SWB+ will continue to support the whole board until the radio is
turned off.
Radio will be turned-off on two conditions;
1. M turned off
2. Low battery
When low battery level is detected by the microprocessor through both conditions above, it will store
the radio personality data to EEPROM before turning off.
Figure 1-1 DC Power Distribution Block Diagram
Control
On/Off Switch
SWB+
Fuse
Low Battery
Detect
Ant. SW
PCIC(ALC)
PA, Driver
LI Ion
3.5V
Reg.
7.5V
Audio PA
4.0V/3.3V
Vddd
Reg.
5V
ASFIC_CMP
VCOBIC
FRACTN
IF
LCD
Driver
5V
RF. AMP, IF AMP
Ext. RX.
MECH.
SWB+
UNSWB+
TX.
Vdda
Reg.
Int/Ext Vdd
R1
R5
R2
R3
Vdda
Accessories
20 pin Connector
Keypad/Option Board
Prime Expansion Board
Switching
Reg.
R4
Vddd
Battery
Reg.
MCU Micro P, ROM
& EEPROM
Buffer (NU)
Led
Jumpers
Dual Vdd
Regulator
Scheme
Single Vdd
Regulator
Scheme
R1 Y Y
R2 N N
R3 N Y
R4 N N
R5 Y N
Vdda Y N
SW. Reg. N N