Other Parts Discussed in Thread: TPS54561
The TPS54561 is intended to be used to both provide 6.9VDC at 3.5 Amps and also charge a 6 Volt Sealed Lead Acid battery.
The switcher circuit is replacing the regulator section of a legacy (circa 1968) linear supply.
The switcher input is powered by from an AC Line powered full wave rectified 12 volt supply. The input supply includes a 2,500 uF capacitor on the output.
At Issue: When AC power fails, and the output voltage becomes less than the battery voltage, the TPS5461 allows conduction from its output back to its input. Our testing has not (yet) resulted in any device failures, however we believe there may be a potential for failure. This "back feeding" does not have a corresponding parameter in the data sheet.
We have not yet tested the case where the 2500 uf cap has been fully discharged and the battery is connected (we only have one EVM).
The first inclination is to place a schottky diode in series with the input of the TPS54561evm to prevent any damaging currents during an AC power fail.
Is the schottky solution viable, or is another switcher more appropriate for the circuit?
