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