I made my own Arduino-like board. I have a 7805 on it to provide +5V, but sometimes I need to power the board by the +5V/GND pins, bypassing the regulator (using an external one). This works perfectly, but I was wondering: what happens to the onboard regulator when I feed +5V on its output pin? Can …

Protecting Voltage Regulator

Grumpy_Mike October 25, 2012, 11:20am 8

1117's for example don't like that much.

True but the OP was talking about an 7805.