Power Supply - Tait TB8100 Service Manual

2.7

Power Supply

RF Board
Digital Board
TB8100 Service Manual
© Tait Electronics Limited September 2006
Refer to Figure 2.13 on page
The reciter is designed to operate from the +28V regulated supply provided
by the PMU. The nominal +28V supply enters the reciter digital board and
passes through an overcurrent and overvoltage protection section before
being distributed. The protected +28V output supplies the control
comparators, fan switch, and main regulators. There is one regulator on the
digital board and another on the RF board.
The main regulator is a switched mode converter that has two outputs: the
flyback portion generates +8.5V, and the buck portion generates +5.3V.
The +8.5V supply is regulated to +8.0V for reticulation to the RF circuits,
either directly, or via switching circuits used in power saving modes. The
+8.5V supply is also used to power the analogue sections of the system
interface board (via the digital board).
The +5.3V supply is regulated to +3.3V to power the RF synthesizers.
The RF board has a charge pump converter that generates +23V from both
the +5.3V and +8.5V supplies. This is used to supply the active loop filters
of the RF synthesizers. The +8.5V output and the +5.3V supply to the
charge pump can be switched as part of the power saving modes.
The main regulator is a switched mode converter that has two outputs: the
flyback portion generates +5.3V, and the buck portion generates +3.3V.
The +5.3V output supplies the op amps associated with the CODECs and
is distributed with regulators: +5V for the ADC, +5V for the system, and
+3V for the 40MHz clock circuitry. The +5.3V and +5V regulated
supplies can be switched as part of the power saving modes.
The +3.3V output is distributed to the remaining circuitry and to the
+2.5V regulator for the DSP. These are switched as part of the power saving
modes. The +3.3V output is also supplied to the system interface board via
a protection circuit.
60.
Reciter Circuit Description 59