TB8100 Service Manual Power Management Unit Circuit Description 201© Tait Electronics Limited September 200612 Power Management Unit CircuitDescriptionThe TB8100 power management unit (PMU) provides stable, low-noise28VDC outputs to power the TB8100 base station. The PMU is made upof a number of individual boards and cards which comprise two mainmodules, the AC module and the DC module. The auxiliary power supplyboard is optional.The AC module accepts an input of 115/230VAC 50/60Hz nominal, andthe DC module accepts an input of 12VDC, 24VDC or 48VDC 1 nominal(depending on the model). Both modules provide the following outputs:■ 28VDC high current (PA)■ 28VDC low current (reciter)■ 13.65VDC, 27.3VDC or 54.6VDC low current (with the optionalauxiliary power supply board).The PMU is available in three main configurations:■ AC PMU (AC input only)■ DC PMU (DC input only)■ AC and DC PMU (both the AC and DC modules are fitted to allow bothAC and DC inputs).If both the AC and DC modules are fitted, the PMU uses the AC input bydefault, and provides battery back-up by operating from the DC input if theAC input is interrupted. The changeover from AC to DC input, and fromDC back to AC input, is breakless. This allows the base station to operatewithout interruption.The power supply card allows efficient use of the DC input at low powerrequirements. The optional auxiliary power supply board provides outputvoltages which are different from the 28VDC required by the TB8100 basestation.Figure 12.1 on page 202 shows the configuration for an AC and DC PMU,along with the main inputs and outputs for power and control signals. Thetable which follows shows which boards and cards are fitted in each module.The locations of the main circuit blocks on the boards are shown inFigure 12.5 on page 211 and Figure 12.6 on page 213.1. Because the DC module is designed to run from a battery, there will be aminimum start-up voltage when operating on DC only (refer to theTB8100 Specifications Manual (MBA-00001-xx) for more details).
