I have a microcontroller with a program that remains in "sleep" mode 99.9% of its life. During this sleep mode, it drains less than 1 microamp with an operating voltage of 2.0V to 3.5V. When it finally is awake, it has a short burst of 2.2 mA consumption that lasts about 10 ms.
Elsewhere in the circuit, I have a 12V battery being used. I'd like to save physical space by eliminating my 3V battery and just tapping off the 12V battery with a 12V to 3V converter.
It seems like most linear regulators and switching converters I've found have very very awful efficiency at low current consumption.
Does anyone have a novel solution to regulate a low power device, relatively efficiently?