I have a circuit that runs on 3.3v. I want it to be able to operate on two AA batteries down to about 2.2v (or until batteries are dead), and also with a 9V power supply. When the power supply is plugged in, the batteries should be disconnected.
The power jack being used has a switching ability, and would work fine if both power sources were at the same voltage. But when battery power is active, the voltage must be boosted to 3.3v, and when the power supply is plugged in the voltage must be regulated down to 3.3v.
I've not been able to find a single chip that will accept 2-9v and regulate at a 3.3v output.
What other solutions are there? Minimal parts count and cost is certainly preferred.