How do I use an external power supply with DISCO F4 development board

[LMorr.3]

I have a DISCO F4 development boards and learning more about it.

I want to build an external power supply board with a 5v regulator to power the DISCO board, while it is still connected to USB so that I can program and debug as usual. I need the external power supply board since I will have other prototype daughterboards with the DISCO will communicate with over i2c and SPI so I need all boards to share a common power source and ground.

It was recommended that I feed 7v into a 5v regulator, and use a BAT60JFILM to connect to pins P2.3 and P2.4 on the DISCO board. This is not clear to me. I checked P2.3 and P2.4 and they both show almost 5v. Do I feed my 5v external power source into those pins even though they already show power? Is that why I should use a BAT60JFILM, but if so, which direction does the BAT60JFILM go, towards the DISCO or towards my external power supply board?

Looking at the DISCOF4 schematic, I see the BAT60JFILM for USB 5V in, and 3V as well... am I correct to assume my external power board will have 5V feeding into a BAT60JFILM and then into P2.3 and P2.4 and the BAT will point towards the DISCO to prevent power from feeding back into my external power supply?

Sorry in advance if I'm stating the obvious.

Rgds

[Jaroslav JANOS]

Hello,

yes, I think you are correct. But just to be sure we are on the same page here:

The D1 diode (already on the board) prevents backfeeding of the USB from your external supply. In the same way should the diode D? (you should place this before the pins) prevent backfeeding of your regulator when it is not active, but USB power is.

Jaroslav