why is LD3 (red power led) working with 3V3 input on NUCLEO-F072RB ?

[mete]

I have this board (revision C-04) with ST-LINK removed (PCB cut off), so the power 3V3 is supplied from CN7. It works fine, but the red power led (LD3) also works. LD3 is, I think, connected to the 5V net, and 5V to 3V3 regulator should not be working but then why the LD3 is shining red?

[waclawek.jan · Accepted solution]

> 5V to 3V3 regulator should not be working

Many LDOs have built in reverse diode from output to input. 

JW

[mete]

I checked the datasheet, but I didn't see something like that. It makes sense, thanks.

[EZHON.1]

In this case, the SB2 should be removed to avoid any damage for LDO.