3-2 DC Power Distribution: DC Regulation and Distribution
The following regulators are used:
The 5 V source from U505 is applied to:
• RX back end circuitry
• RX/TX audio filters
• 1/2 VCC generator
• VCO power source (Q705, Q706)
• RX B+ (Q304)
• TXVB (Q407)
• VCTCXO
The 5 V source is also applied to transistor switches Q304 and Q407. Q304 is turned on by Q305
when RX_EN (from U101 Pin 71) is high, and supplies the source to mixer, IF IC and LNA. Q407 is
turned on by Q408 when TX_EN2 (from U101 Pin 85) is high, and supplies the "TXVB" source to the
first transmitter stage Q401 base, Q402 gate, APC power source (U401 Pin 8) and ANT switch
(CR401).
The 3.3 V regulated source from U506 is applied to:
• MCU IC U101
• EEProm IC U104
• DTMF IC U103
• Audio processor IC U102
• Microphone bias circuitry
• And applied to Key PCB (LCD driver power source)
The 10 V source from U507 is applied to Charge Pump.
Table 3-1. Voltage Regulators
Reference No. Description Type
U505 5V regulator TK11250
U506 3.3V regulator TK11233
U507 Voltage Doubler (10V) TC12140
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