I have a commercially produced circuit board with an on-board 7805 regulator. It was designed to be powered from 9-12 volts input to the regulator. The 5 volts powers a bus on the board, but all the main board circuitry runs from a separate 3.3 volt regulator which is powered from the 5 volt bus.
I want to run the board from 4 NiMH batteries, which emit from about 5.5 to 4.5 volts depending on their charge state.
What I've done so far is to connect the NiMH batteries directly to the 5 volt bus on the board, and it seems to be working fine. The 7805 appears to have no problem receiving this varying voltage on its 5 volt output pin.
But to charge the NiMH batteries in-circuit, the voltage on the 5 volt bus may run up into the 6 or more volt range.
Does anyone know if applying this voltage to the 7805 output pin is a potential problem?
I've looked over a 7805 data sheet but it doesn't say anything about this unusual usage of the regulator.
I could unsolder and pull the 7805 out of the board but I'd rather not hack the board itself if applying this voltage to it would be completely harmless.
I want to run the board from 4 NiMH batteries, which emit from about 5.5 to 4.5 volts depending on their charge state.
What I've done so far is to connect the NiMH batteries directly to the 5 volt bus on the board, and it seems to be working fine. The 7805 appears to have no problem receiving this varying voltage on its 5 volt output pin.
But to charge the NiMH batteries in-circuit, the voltage on the 5 volt bus may run up into the 6 or more volt range.
Does anyone know if applying this voltage to the 7805 output pin is a potential problem?
I've looked over a 7805 data sheet but it doesn't say anything about this unusual usage of the regulator.
I could unsolder and pull the 7805 out of the board but I'd rather not hack the board itself if applying this voltage to it would be completely harmless.