Tait TB8100, Service Manual, Page: 205 / 306

TB8100 Service Manual Power Management Unit Circuit Description 205
© Tait Electronics Limited September 2006
The microprocessor monitors the battery input voltage and the temperature
of the DC module heatsink. It also identifies the model of DC converter
fitted to the DC module (i.e 12V, 24V or 48V nominal input).
Standby Power
Supply
The microprocessor detects whether this power supply is fitted, and disables
it when the AC mains supply is operating.
The output from this power supply can be isolated from the reciter output
to maintain power to the microprocessor when battery capacity is low. The
low battery threshold is set with the Service Kit.
This power supply is also used to maintain power to the microprocessor
when the PMU is in deep sleep mode and the DC converter is switched off.
Deep sleep mode is configured with the Service Kit and can only function
if the load on the PMU reciter output is less than 10W.
If the power supply is not fitted, the microprocessor is powered by an
internal 5V power supply derived from the main PA output.
Auxiliary Power
Supply
The microprocessor controls the on/off function for this power supply. The
actual operation of the power supply is set with the Service Kit:
■
on only when AC mains is present
■
controlled by Task Manager.
The microprocessor detects when the power supply is operating. It also
detects which model of power supply is fitted (12V, 24V or 48V), whether
the power supply is operating or not.
Front Panel Fan
The microprocessor measures the current drawn by the PMU fan mounted
in the front panel. It protects the fan driver circuitry from overload or short
circuit by switching the fan off for five seconds, and then switching it on
again. The microprocessor will continue to try running the fan indefinitely.
If the fan has failed, the reciter sends an alarm to the Service Kit.
I
2
C Communications
The microprocessor controls the I
2
C communications between the PMU
and the other base station modules.
The current source used by the I
2
C lines as active pull-up resistors is housed
on the microprocessor board.