Will this work?
I have a PCB that requires both 5v and 3.3v operation. It has a 3.3v and a 5v linear regulator on it (type LD1117). I can power the board from an external 9v source, but I also want to be able to power it from USB, if the USB is connected to the jack.
This means that the power to the board could come from the 9v source only, the USB only, or both could be connected. I have come up with this schematic and I wanted to make sure this will work. If the Power line is connected, I get power to both the regulators. If the USB is connected, I get 5volt power on the 5volt rail and 5v (minus the diode drop) to the regulators.
If this doesn't work, do you have any other suggestions?
**broken link removed**