USB Bus power

[mat72]

I'm building a USB device that can be power by a external 5V supply or from the USB bus. The device can be used without USB, so i need the option of the external 5v source. I have a 5V regulating circuit for the external source. The 5V external source and usb bus power are both connected in parallel.

Should I use a diode on the USB +Vbus in case both sources are connected and the USB connection is in sleep mode?

Thanks,

Matt

 

[Someone Electro]

Yea diodes should do

 

[mat72]

Should it be placed directly from the +5V on the USB connector to +5V on the board?

Thanks,

Matt

 

[Someone Electro]

From 5V to board and from USB to board.

This way curent cant flow betwne the 5V and usb

 

[justDIY]

I don't know what your application is, but I ran across this the other day

MAX155x - it is a lithium battery charger, which autodetects USB or external power sources:

https://www.sparkfun.com/commerce/product_info.php?products_id=674

**broken link removed**