Voltage Regulator Reverse Bias

So I have a custom built PCB that supplies power to an Arduino. The picture below shows how I have the circuit hooked up now. I have two issues with this design.

  1. The 3.3V regulator is only active when the Battery is plugged in and not when the USB is plugged in.
  2. When there is no battery plugged in, and is just powered off USB, the voltage will travel through the 5V regulator and come out of Vin, causes some minor issues elsewhere.

I am pretty sure I need to add some Schottky diodes in this circuit, but I am trying to figure out the best way to add them without shorting anything. Thanks for the help!

P.S. There are capacitors in this circuit for smoothing, but I do not have them shown in this circuit for simplicity.


How about...


(Edited: diodes labelled D2,D3)


Did you prototype your circuit before committing to a PCB?

This the sort of question that should have been asked before making PCB.

Tom... :slight_smile: