Need some advice:
I have PIC18F2450 based USB device that has dual power: USB and external power with TL2575-05 regulator.
Device should be able to run if at least one source present (USB is not plugged in all the time).
For now I use two diodes to prevent USB backfeeding, but forward voltage drop 0.8V over diode brings PIC to the lower spec margin of 4.2V.
I am exploring the idea to use Enable signal on TL2575 to shut it down when USB is active, but not sure if this is a good idea.
So, any ideas how to handle it?
Needs to be something simple and cheap...
I have PIC18F2450 based USB device that has dual power: USB and external power with TL2575-05 regulator.
Device should be able to run if at least one source present (USB is not plugged in all the time).
For now I use two diodes to prevent USB backfeeding, but forward voltage drop 0.8V over diode brings PIC to the lower spec margin of 4.2V.
I am exploring the idea to use Enable signal on TL2575 to shut it down when USB is active, but not sure if this is a good idea.
So, any ideas how to handle it?
Needs to be something simple and cheap...