LiPo seems the obvious choice - being closest to the 3.3v needed, but I need to step it down (and up?) and regulate it to 3,3v need from the 3.2 - 4.0 volts which LiPos deliver throughout their charge range. Even if LiPos are not the best choice - there is a need to convert and stabilise fluctuating voltage around 3v - 6v to 3.3v.
The so-called high efficiency digital regulators I have burn 17mA with nothing connected to them - so they are immediately ruled out.
Is there a clear winner product for this scenario?