[catch23]

If you want to extract the most out of your batteries, wouldn't you use a boosting reg so can extract every last bit? I think for most projects, the uC uses far less power than the auxiliary components around it, like a LED. If you boost the voltage you can use higher logic levels. There are many examples boosting a "dead" 0.5V AA battery to 3V at a lower current.

If you use a buck regulator, you could use starting voltages beyond the chip's max voltage limit and burn the power past a typical dead cell's voltage levels -- start with a 12V battery using 1.8V logic and burn the battery down to 2V -- probably around 98% used.

I think you'll find that most projects out there use a voltage regulator because you can use up "more" of the battery this way.

[theatrus2]

Boosting regulators are common, but there are efficiency tradeoffs, since: a) boosting regulators consume energy, b) boosting regulators with a sleep mode (so you're not spinning the wheels 24/7) don't start up immediately.

Two 0.9V alkaline cells can still power most microcontrollers, especially in sleep mode, and red LEDs will still light. If you really need higher voltage, than the boost is the way to go.

I previously worked off of an MSP430-turned-EFM32 product which had a MCU+radio lifetime of 5-7 years on 4-AA cells (two paralleled). Most switcher solutions we looked at wouldn't have netted a measurable increase in runtime due to the much higher sleep currents in those units compared to even the MCU.

[mbell]

A big reason most hobby boards use LDO regulators is that buck-boost topologies are comparatively complex. PCB layout is critical and protections are more complicated.

You'll have a really bad time if you try to build a buck-boost switcher in a breadboard and won't have a clue why its not working. On the other hand you can throw an LDO into a breadboard with a couple caps and be pretty confident it'll just work.

[hansc]

You are absolutely right: Once you get the uC power consumption down with sleeping, others components use the majority of the power and determine battery life for the most part.