Diode... Help with value

[Lxkev]

Hello.

I have a pcb that has two power supply's of 5v DC.

PSU A - esp32
PSU B - pixels

The circuit powers a esp32.. The esp32 board can trigger a relay that turns on the PSU H which powers a set of fuses on the PCB that is used to power up some pixels.

On the the PCB I have a jumper between PSU A and PSU B so that I can run it all of one PSU.

My concern is that one day I'll forget to remove the jumper and power both and get a nice bang.

So can I put a diode after the jumper so that I can power the esp32 from PSU B.. And stop flow back from accidentally happening from PSU A.

The esp32 I'm using needs 3amps.

What's size diode do I need?

 

[danadak]

Generally speaking :

1) Diode V drop affects noise margin for logic level circuits. Investigate if
this is an issue with downstream loads.

2) "Usually" one uses a Schottky to minimize Vdrop. Be aware if you are doing
low power work there is leakage associated with Schottkys. Or use super barrier
diodes -

Lowest voltage drop diode possible

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This article introduces the SBR, explains its characteristics, and discusses how it may be used in an example application of automotive daylight running lamps.

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Low drop, set filters.....

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Regards, Dana.