Arduino Nano 5V Selector

Hi everyone,

I noticed that the nano uses a different power selector than the uno and other boards. The nano simply uses a schottky diode to ‘select’ between the two ( I have attached a screenshot below). I’m wondering how does this actually select the power source? If both usb + external supply are connected to the nano does it actually choose a power source or does it draw current from both usb and the external power source?

Thanks in advance

If external power is connected, and the regulator is outputting 5v, the voltage difference across that diode will be ~0v (well, possibly .1v, since many USB power sources put out an extra tenth or two to improve charging performance on cheap USB cables). But in any event, with the shottky diode requiring a voltage drop of 0.3v, the power will be coming from the external regulator (unless you draw so much current that it overheats and turns off (depending on whether your clone uses a 1117 or one of those dinky ones in SOT-23 like the pro mini does, this may be easy to do), in which case the USB power will take over, if present)