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By rimakus
#194760
Hello all,
I was wondering if someone tried running Pro Micro using 11.1v 3S Lipo via RAW pin. The reason why I am asking is because when fully charged 3S LIPO battery has approx 12.6 volts which is above 12V for powering over RAW pin according to documentation. The board itself will be controlling motor connected to same LIPO battery via MOSFET by supplying 5V voltage to the gate from one of the PWM capable pins.
Thanks in advance.
By Valen
#194801
That's probably pushing the limits. The thing is, depending on the amount of current that your end-design is going to consume, the voltage regulator has to turn that voltage difference (12.6 -5 volt) into heat (voltage times current). I don't know how much that chip can handle before it fails. If that is the ONLY thing it does, running the program and signalling the mosfet gate, then it is probably ok. The Pro Micro is designed with the intent to power more external parts with the 5 volt. If the other output pins also need to power leds or other sensors or whatever, increasing the total current through the voltage regulator may damage it in the long run. Such small surface mount chips have little surface area to get rid of the heat. Mounting a heatsink is going to be very tricky. I would opt for a seperate voltage regulator (with enough upside on the input, and prefferably through hole with a lug to connect a heat sink if needed) and connect that to the 5 volt instead. Bypassing the onboard regulator. But I'm just a play-it-safe guy.
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By phalanx
#194815
Interestingly enough, the datasheet for the MIC5219 has a max power calculation example using the SOT-23-5 package used on the Pro Micro along with using the thermal values of a minimum footprint (which is what the pro micro has). It's max dissipation in this case is 455mW. With a 7.6V drop across the regulator, you get just under 60mA before you reach max dissipation. Active supply current for the Atmega at 5V and 16MHz is about 13mA. I wouldn't expect that driving a MOSFET will consume much current so you are likely safe from a power dissipation standpoint. It wouldn't hurt to have some airflow across it though.

The more interesting detail in the datasheet is the operating ratings of the part. Vin has a listed range of +2.5V to +12V outside of which its operation is not guaranteed. Will that cause a problem? Probably not at 12.6V but your mileage may vary. The absolute max supply voltage is ±20V so you are safe in that regard.

-Bill