I've been toying around with 3V3 regulators trying to find something with a low quiescent current to extend battery life as much as possible. All the regulator is powering in my circuit is the Atmega328P-PU which spends most of its time in sleep mode.
Originally I tried an AMS1117 Fixed 3V3 regulator but found that on its own it drew around 3.5 - 4mA. Admittedly I should have checked the Data Sheet which says Typical Quiescent current is around 5mA but I had them to hand so thought I'd try it and see.
I've since found two potential replacements which are also Fixed Voltage Regulators but draw considerably less quiescent current than the AMS1117.
The first candidate is the LM2936 in SOT-223 package. This claims to have a low quiescent current of around 15uA BUT it is only rated up to 50mA.
The next is the MIC5209 (also SOT-223) which will supply 500mA but draws around 170uA Quiescent Current.
The job of my Atmega is to check the time and then switch other devices on which are powered from a separate 5V regulator (which also has to be turned on by the Atmega). I can't see this taking 50mA to do but I've ordered both of the regulators I've listed just in case the LM2936 isn't man enough.
Maybe one of these regulators would be suitable for your application?