Hello! I have this problem with Leonardo 5V Auto Selector circuit
You can see its schematic below…
When you look at this 5V auto selector part, it uses a FDN340P, which is a P-MOSFET, I believe when there is no output from LMV358 the MOSFET should be set On, so the power from USB port could get through it to the voltage regulator, which give a 3.3V output. But strange thing is, the VUSB port is connected to its D(Drain), from the experience making H-bridges for my robot I know the circuit should come from S(Source) to D(Drain), thus I think VUSB port should be connected to S(Source)
I looked into the PCB file in Eagle too, just to find VUSB port is connected to D, on that P-MOSFET, which confused me a lot, someone can help me get this confusion out of my mind o.O
Thaanks in advance && Cheers!