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I'm stuck between choosing to use either a buck converter or a LDO voltage regulator for my heated glove project. The voltage regulator's function in question will be to power the microcontroller. What I am having trouble deciding on is which is better for low power applications. Low power as in powering a microcontroller that draws only a few uA of current. So in any case, which would be better for my project: a buck converter or a low quiescent LDO? Or does it not matter in this case.

Voltage Regulator: LM2936MPX-5.0/NOPB

Voltage Regulator Datasheet

Buck Converter: LMR14203XMK/NOPB

Buck Converter Datasheet

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    \$\begingroup\$ What quiescent current has LDO and what buck regulator? What's the input voltage, what's the output voltage. What current will the microcontroller require? What's the capacity of your battery? If it's for heater, how long should the battery supply power? \$\endgroup\$
    – Chupacabras
    Aug 25, 2019 at 5:42
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    \$\begingroup\$ Or better as in cost ( cheapest), weight or size... \$\endgroup\$
    – Solar Mike
    Aug 25, 2019 at 6:15
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    \$\begingroup\$ If you are discussing extremely lower power systems and you want the absolute best that can be had, then you will probably be designing one yourself. It's not overly complex, but details matter a lot. But your question seems to me possibly misguided. An LDO's objectives relate to situations where only a low dropout is allowed. But the goal posts are placed differently than your case, I think. Sure, it's natural to assume that the lowest voltage drop would imply the lowest wasted power. But without knowing your source of power, in detail, and the needs as well then not much can really be said. \$\endgroup\$
    – jonk
    Aug 25, 2019 at 6:21
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    \$\begingroup\$ Your question can be made narrower by stating the input battery voltage, load (MCU only or heating gloves too?), Battery life needed? Space or price constraints? \$\endgroup\$
    – User323693
    Aug 25, 2019 at 6:44
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    \$\begingroup\$ Much depends on the specifics of the application; I looked at this a while back. electronics.stackexchange.com/questions/275605/… \$\endgroup\$
    – Peter Smith
    Aug 25, 2019 at 10:15

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as your micro controller is only drawing such a tiny amount of power, an LDO with a low quiescent current, ideally lower than your microcontroller, will likely end up more efficient, most inductor based switching converters struggle at very low loads,

e.g. the LDO you linked draws 15uA at idle, so your power wasted is (the supply current of your micro * The voltage your dropping) + (15uA * the input voltage)

The switching converter has a 1350uA quiescent current, however you can see on the graphs used that the efficiency of the converter falls off to nothing at low currents, so under ideal conditions, you will be burning atleast (9 times the supply current of the micro * the output voltage) + (1350uA * input voltage)

As an alternative there are switched capacitor buck regulators, this would sit fairly close to the LDO for sub 1mA supply currents and a low voltage drop, whether it is better or worse would require knowing exactly how much current you need and how large the voltage drop is.

edit: deceptive idle current on the switching regulator,

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  • \$\begingroup\$ there are converters that use auto PFM and are synchronized buck converters, you could get very low quiescent with those, i've used some with only 2-5uA quiescent. \$\endgroup\$
    – TheAnimatrix
    Sep 11, 2022 at 17:15

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