I'm building an optical wireless mouse based on nRF52833 and a 16340 cell, I need a sanity check on some considerations regarding the DC regulation.
The battery voltage goes from 4.2V when fully charged to 2.5V when fully discharged, so to power the nRF52 at 3.3V I need a buck/boost converter. I have selected TPS63031 for the job.
I'm running the nRF52 at 3.3V because according to this it draws a lot less current than it would at, for example, 1.8V or 2V. If I were to use those voltages I could just use a linear regulator instead of the buck boost.
During normal operation I estimate the MCU to be drawing between 1mA and 10mA, and when the MCU is sleeping something between 1uA and 10uA. If we look in the datasheet for efficiency figures we see that the 1-10mA range is fine, but 1-10uA has not been characterized, going as low as 100uA.
Would the regulator output be stable (enough) when the load is less than 100uA? Judging by this very similar question with a very similar regulator I assume the answer is yes, but the output would have some extra ripple because of the power save mode that is also present on my selected regulator, although not as well explained in the datasheet.
Assuming the output is stable in the 1-10uA range, the efficiency of the regulator would be terrible, but would this even be a problem? Let's say the efficiency is 20% at 10uA, does this mean that to get those [email protected] the regulator would have to waste 80% of that, i.e. 50uA, for a total of 60uA plus the quiescent current of the regulator (35uA max)?. Is my understanding of efficiency in this context correct? If it is, I wouldn't call this current waste optimal, but certainly low enough to be negligible.