Motorola pro7100 Manuel de service télécharger pdf (Page 17)

Theory of Operation 2-3

Figure 2-2. DC Power Distribution Block Diagram

The INT SW B+ voltage from switching transistor Q0661 provides power to the circuit controlling the

audio PA output. The voltage is monitored by the µP through voltage divider R0671/R0672 and the

line battery voltage. Diode VR0671 limits the divided voltage to 5.6 volts to protect the µP.

Regulator U0611 generates the voltage for the switched supply voltage output (SWB+) at accessory

connector J0501, pin 13. U0611 operates as a switch with voltage and current limit. Resistors

R0611/R0612 set the maximum output voltage to 16.5 volts. This limitation is only active at high

supply voltage levels. The regulator output is enabled by a 0 volt signal at Q0661, pin 2. Q0641 and

R0641 disable the regulator when the radio is turned off. Input and output capacitors C0603 and

C0611/C0612 reduce high frequency noise.

Diode VR0601 protects against transients and reverse polarity of the supply voltage.

2.2.2 Automatic On/Off

The radio software and/or external triggers turn the radio on or off without direct user action. For

example, automatic turn on when ignition is sensed and off when ignition is off.

Q0661 provides the INT SW B+ voltage to the various radio circuits and to enable the voltage

regulators via transistor Q0641 which contains a pnp and an npn transistor that provide an electronic

on/off switch. The switch is on when the collector of the npn transistor within Q0661 is low. When the

radio is off the collector is at supply voltage level. This effectively prevents current flow from emitter to

collector of the pnp transistor. When the radio is turned on the voltage at the base of the npn

transistor is pulled high and the pnp transistor switches on (saturation). With the INT SWB+ voltage

now at supply voltage level, transistor Q0641 pulls pin 2 of the voltage regulators U0611 and U 0641

to ground level, enabling their outputs.

The electronic on/off circuits are enabled by the µP through ASFIC CMP port GCB2, line DC

POWER ON, emergency switch (line EMERGENCY CONTROL), the mechanical On/Off/Volume

knob on the control head (line ON OFF CONTROL), or the ignition sense circuits (line IGNITION

CONTROL). If any of the four paths cause a low at the collector of the npn transistor within Q0661,

the electronic "ON" is engaged.

VCOBIC

FRACTN

VSTBY

5V_RF

9V3

FLT_A+

5VD

SWB+

Option Board

40 Pin Connector

PA, Driver

Antenna Switch

Control Head

12 Pin Connector

Accessories

20 Pin Connector

J0601

13.2V

PASUPVLTG

FLT_A+

12V

Regulator

ON / OFF

Control

ASFIC_CMP

5.6V

Ignition

Emergency

ON/OFF

9.3V

Regulator

Audio PA

Regulator

5VD

Regulator

5V/

VDDA

MCU

µP, RAM,

FLASH & EEPROM

PCIC,

TX Amp

Te m p S en se

RX RF Amp

IF Amp

1 2 ... 12 13 14 15 16 17 18 19 20 21 22 ... 108 109

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Motorola pro7100 Manuel de service Page 17

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