I have a fistful of Pro Mini clones with atmega168 ICs. Oddly they have 16MHz crystals. When I feed it nominal 3.7V (really 4V, but it will spend most time around 3.7) via the RAW pin, I see 2.6V on VCC and RST pins. Of course I’d like a bit more for my MOSFETs - what’s the cause of this? It’s a 1.4V drop, is this common for pro minis?

I can feed 3.3V to VCC with a regulator, but the 16MHz crystal is puzzling. Clocked for 16MHz?


1 Answer 1


Bypass the regulator, and connect the battery directly to the VCC pin. However, running at 16Mhz requires at least 3.8 Volts, according to the datasheet. Lower voltages may work, but aren't guarantied.

  • Yes, I did that, and it works as one might expect. The chinese have made many wonderful arduino clones; this is a collector’s item... (I also have a Nano with a 12MHz crystal). In any case my problem has been resolved.
    – user2497
    Commented Feb 27, 2018 at 16:32

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