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By davydnorris
Pablo2048 wrote:
davydnorris wrote:I built some modules for testing using dry cells and loaded them up with 3 x D cell batteries in series. Those with a 3.3V LDO were dead in a week, whereas the buck converter lasted months. You could feel the heat coming from the LDO as all that power wasted into the environment.

Of course, but this is merely hypothetical test with near constant huge current. Here we are speaking about consumption over whole device range - say 100uA to 500mA peaks. This device would spent 99% of time sleeping, consuming just few uAmps and this is exactly the range where SMPS would fail.

Ummm no it was an actual test with my firmware running and doing what it needs to do. I would put it to you that unless you have actually done a comparison test, your estimation using data sheets is the hypothetical :-)

I ran it with 30 sec sampling periods, 5 min deep sleep.

Pablo2048 wrote:Well the ISL9110 has quiescent current of 35uA LDO XC6203P332PR has quiescent current 8uA. If we rely on 100uA sleep current, the power consumption of ISL9110 would waste nearly 30% of energy. Also the diagrams of ISL9110 efficiency starts at 10mA, but we are talking of 100uA so we are unable to determine, how efficient the conversion would be. The ISL is constructed for shutdown and run only when necessary, but this approach complicates the whole schematics because we need external timer and/or cpu to start the converter. So my opinion is that in this usecase the LDO wins...

Back up your opinion with actual data - that's what I did because I was not understanding the LDO data I was getting. My evidence shows the buck converter to be a clear winner and I'm very happy.