I've got a project I'm working on that is powered by a single Lithium-Ion battery (let's say design range is 2.5V to 4.2V), and a nRF52832-based MCU. I've decided to design a power topology that goes from raw battery to a "system" rail of 2.5V, and then feed that to all devices + the nRF52's internal DC/DC regulator.
My design target for "sleeping" power consumption here (i.e., idling until event occurs) is around 300uA or so. I don't expect peak currents on the rail to ever go past 20mA or so as well -- going by the nRF datasheet numbers (taken with grain of marketing salt), they claim ~15mA or so of current consumption.
So, I've obviously got a concern about the quiescent current (Iq) of my chosen regulator, which I'm basically stuck with based on the manufacturer. But, I also have a concern about a buck controller going into pulse-skipping or similar mode and giving me a great EMI/EMC problem to deal with.
The largest possible voltage delta (4.2V - 2.5V) gives me some pause using a LDO/linear part (~55% efficiency). I've looked at the AP3401, primarily because it is incredibly cheap. The datasheet is very light on the details, but it mentions pulse-skipping once. I imagine running at very low currents relative to the 1A number is going to put me in that range.
This TI TPS62740 naturally has a better datasheet, and seems like a "better" part for this / intended for these low-currents, but it also appears to quite literally be 8x the cost of the AP3401.
- Recommendations / literature on very low-current switching regulator applications?
- Experience with / stories about dealing with EMI-related issues with a regulator that is basically always pulse-skipping?
- Suck it up and go with a linear regulator? Some kind of scheme that switches based on the system state?
- Recommended solutions from previous experience? Target volume I believe is around 10K units/yr.