Can I connect an external 3.3V power to the 3V3 pin?

If I don’t connect the USB cable to XIAO SAMD21, can I connect an external 3.3V power supply to the 3V3 pin (pin 11, counting from 0) without a risk to damage anything?

Hello, the answer is you can supply power by the 3.3v pin but we suggest you would not do it: because Voltage input connected to general I/O pins may cause chip damage if it’ higher than 3.3V, but the pin of VIN on the solder pad of the back board is designed for power supply, it connect to a voltage regulator module so it is safe

I am a bit confused: you wrote “we suggest you would not do it” and also “so it is safe”. Anyway, thank you for your attention.

Hi, he means that it is recommended that you do not use 3.3V pin power supply. Using VIN on the back of SAMD21 is safe rather than 3.3 V pin

I see, thanks.


  1. pin 3V3 is not a general I/O pin;
  2. the VIN pad on the back, which you highlighted, is directly connected to the 5V pin and hence to the voltage regulator 5V->3.3V input, so it makes no sense to connect 3.3V power supply there.

Thank you, anyway.