Motorola MTP700 Detailed Service Manual page 56

4.1 - 22
3.3V Switching Regulator
An external 3.3V switching regulator is used to convert the battery voltage (7.2V) down to
3.3V to be used by GCAP3. This regulator can be set to fixed frequency 600KHz (during
Tx & Rx) or variable switching frequency (when idle) depending on the load.
PWM #1 (Pulse Width Modulation)
PWM #1 is a selectable step down switching regulator. It is selectable using the RedCap2
SPIB bus from 1.2V to 2.45V in 6 steps, Pass Through and Power down modes. The
switcher is active during Power Reset (POR) in 1.875V mode. It is set to 1.875V. Switch-
ing regulator is PWM#1_1.875V, which is the supply for the internal core, emulation port
and clock output drivers of the RedCap2. The switcher is supplied from FILT_3.3V and it
is active whenever the radio is turned ON.
V1 Linear Regulator
V1 is a programmable linear regulator. It is programmed using the RedCap2 SPIB bus
from 0.975V to 3.0V in 8 steps. This regulator is active during POR and its initial value is
1.55V. For this radio, V1 is programmed to 3.0V, supplying ESCORT section by filtered
V1_3V. This regulator is active whenever the radio is turned ON.
V2 Linear Regulator
V2 is a selectable linear regulator. It is selectable using the GCAP3 UV_SEL pin (internal
logic) between either 2.5V and 2.775V. This regulator is active during POR and its initial
output value is set by GCAP3 UV_SEL pin. Connecting UV_SEL pin to FILT_3.3V sets
V2 output value to 2.775V, connecting UV_SEL pin to Ground sets V2 output value to
2.5V. For this radio, V2 is selected to 2.775V. This regulator is supplied by FILT_3.3V and
it is active whenever the radio is turned ON. V2 is the supply for internal audio circuits,
CLK_IN input driver and TS interface.
V3 Linear Regulator
V3 is a selectable linear regulator. It is selectable using the RedCap2 SPIB bus from
1.875V to 2.775V in 4 steps. This regulator is active during POR and its initial output
value is 2.775V. For this radio, V3 is selected to 2.775V. The regulator is supplied by
FILT_3.3V and it is active whenever the radio is turned ON. V3 is directly used as
V3_2.775V_DIG, which is the supply for the RedCap2, Flash, SRAM, GCAP3, Display,
logic lines pull-up and 40-pin connector. V3_2.775V is the filtered V3 supply voltage for
the Serial VCC of U1001/WPIC+.
V4 Linear Regulator
V4 is a selectable linear regulator with external pass transistor. It is selectable using the
RedCap2 SPIB bus from 1.875V to 2.775V in 4 steps. It is set to 2.775V. V4 is always
powered from FILT_3.3V and it is active whenever the radio is turned ON. This regulator
is active during POR. V4 supplies via the filtered V4_2.775V the RF sections RFCU,
RXU, TXPA and TXFE whilst the LNODCT section has an extra filtered supply voltage
V4_LNODCT.
VREF1 Linear Regulator
VREF1 is a programmable linear regulator. It is programmed using the RedCap2 SPIB
bus from 0.95V to 2.775V. This regulator is active during POR and its initial value is
2.775V. For this radio, VREF1 is programmed to 2.775V and is supplied by FILT_3.3V.
VREF1 is VREF1_2.775V, which is the supply for the AND Gate on TCXO_WARP line.
MTP700 Portable Radio / Detailed Service Manual TRANSCEIVER 400 MHz