Service Manual
Page 4.9
3 ~ TECHNICAL DESCRIPTION
The Power-off operation requires the On-Off switch to be turned off for more than 2 seconds. If the On-Off
switch is sensed going low by the DSP via the PWR_SENSE line, the DSP will save radio settings and then
lower the PWR_OFF line, thereby turning Q900 off.
4.6.2
Power Supplies
The following is a list of the SRP9100
power supplies and some of the devices and circuits they supply.
4.6.2.1 5V Regulator U900
This regulator can be powered down by a STBY signal from the PLA. Supplies RX_PSU and TX_PSU are
switched via Q903 and Q904. Circuits supplied by U900 are as follows.
• Synthesiser reference oscillator, divider and phase modulator
• VCO Varicap driver
• Switched RX PSU to VCO output switch
• Switched TX PSU to TX VCO enable/Rx VCO disable
• Switched TX PSU to Transmit Buffer Amplifiers
• Switched RX PSU to Receive front end and mixer
• 90MHz local oscillator Q402
4.6.2.2 5V Regulator U901
• Transmit and receive VCO’s
• PLL U701
• Analogue gates U302, U800
• Op amp U760
• 3.3V sub regulator Q910
4.6.2.3 3.3V Regulator U902/Q918
• PLL Synthesiser IC U701
• DSP U201
• Flash memory U202
• PLA U300
• ADC CODEC U1, U820
4.6.2.4 2.5V Regulator U903
• DSP U201
• PLA U300
4.6.2.5 Negative Power Supply U904E/F
• -16V output (-16V) for VCO Varicap tuning drivers
• -12V Output (-12V) for Front end Varicap tuning drivers
4.6.2.6 Switched Battery
•
Transmit Power Amplifier
• Speaker Amplifier