I need a voltage regulator for a project which will handle a voltage on its output pin with no input. (The GND pin may still be connected.) Most devices don't seem to be able to handle this. Are there any which can?
Electronic – Regulator that can handle voltage on its output
voltage-regulator
Related Solutions
Surmises only - hard to be sure for a specific part with no hard data.
Connecting one as stated and measuring current flow into regulator would tell you something.
A look at the block diagram at the bottom of page 5 of the datasheet suggests you will be trying to reverse bias junctions in Q24 & Q26 (top right of page).I'd expect the 4.5-3.3= 1.2V overvoltage to be low enough to have a good chance of being safe.
Is power applied to the regulator during programming? If not you may breakdown internal intrinsic body diodes (which we may not have got). After which anything can happen.
You mention a reverse protection diode. It's not obvious where you were going to put that. It's usual to place a diode from regulator output to regulator input - Schottky probably a good idea.
If your ampere requirements are less than 300mA maybe this could work for you: -
It's 5V, low quiescent current and can be turned off/on with a control line.
Best Answer
You sometimes see a diode connected from the output of a regulator back to the input, such that under normal powered operation, the diode is reverse biased. If you remove the input power, the diode can conduct, and clamps the regulator input voltage to not more than a diode drop below the output voltage.