Motorola Commercial CM Series Service Information page 17

Controller Theory of Operation
The DC voltage applied to connector P2 supplies power directly to the following circuitry:
• Electronic on/off control
• RF power amplifier
• 12 volts P-cH FET -U514
• 9.3 volt regulator
• Audio PA
Ignition
B+
Auto
Ferrite Bit
On/Off
Switch
Filt_B+
Control
On/Off
Control
11-16.6V
0.9A
On/Off
Control
Regulator U501 is used to generate the 9.3 volts required by some audio circuits, the RF circuitry
and power control circuitry. Input and output capacitors are used to reduce high frequency noise.
Resistors R5001 / R5081 set the output voltage of the regulator. This regulator output is
electronically enabled by a 0 volt signal on pin 2. Q502, Q505 and R5038 are used to disable the
regulator when the radio is turned off.
Voltage regulator U510 provides 3.3 volts for the digital circuitry. Operating voltage is from the
regulated 9.3V supply. Input and output capacitors are used to reduce high frequency noise and
provide proper operation during battery transients. U510 provides a reset output that goes to 0 volts
if the regulator output goes below 3.1 volts. This is used to reset the controller to prevent improper
operation.
Voltage regulator U508 provides 3.3V for the RF circuits and ASFIC_CMP. Input and output
capacitors are used to reduce the high frequency noise and provide proper operation during battery
transients.
RF_PA
Audio_PA
Antenna Switch
Power Control
500mA
Acces Conn
FET
Audio PA_Soutdown
P-CH
Power Loop Op_Amp
SW_Filt_B+
U501
9.3V Regulator
500mA
Rx_Amp
PA_Pre-driver
PA Driver
Figure 2-6 DC Power Distribution Block Diagram
9.3V
65mA
0.85A
9.3V
9.3V
75mA
45mA
U503
5V RF Regulator
45mA 50mA
LVFRAC_N
IF_Amp
Control Head
Mic Connector
Keypad
Mic Bias
9V, 5mA
7_Seg
Status LEDs
Bed
7_Seg
to
DOT
7-Seg
Back
Shift
light
Reg
9.3V
162mA
U508
U510
3.3V RF Reg
3.3V D Reg
25mA
micro P
ASFIC_CMP
RAM
IFIC
Flash
RX Cct
EEPROM
2-9
3.2V
72mA
Reset
90mA