is there a protection diode on 5v input (Gem)

yannseznec

I'm starting to lay out my first Gem-based PCB. I'm using the KiCAD symbols and footprints from the project GitHub (which are excellent, by the way).

I'm probably going to use a 5V power supply via a barrel connector. My plan was to just connect that to the 5V pin on the Gem. My question is: is there already a protection diode on the board, in case someone (me) accidentally plugs in a power supply with the wrong polarity? Or should I include that on my PCB?

max

yannseznec Power should enter on P1.1 VIN. If you use the advanced version of the symbol/footprint it's alreaady there, I have added it also to the standard variant, will push it soon to the public repo. Thanks for the flowers 😃

max

The updated symbols/footprint for KiCad10 have marked the multiple GNDs and 3.3V / 5V as internally connected, so less spurious ratsnest lines. They are now in the Bela hardware repository.

max

In the PocketBeagle datasheet on page 26 Section 3.3 you find more information.

yannseznec

excellent, yes, I found the 5v input on the schematic! that's what I'm currently connecting my barrel socket to. I think my main question is whether I should put a protection diode between the barrel socket and the 5v.vin pin, to protect against reverse polarity. Or is that already on the board somewhere? I've looked in the pocketbeagle docs but couldn't find it (though admittedly I didn't look very hard)

yannseznec

oh wait maybe I see it, I just noticed this part of the schematic on page 27, which I guess means there are diodes on each input power option

giuliomoro

You'll see from the PB2 datasheet that this already has a protection diode in series (an "ideal diode", nonetheless), so you won't need one of your own. There's some overvoltage protection on board, but I am not sure how much you can rely on that: just make sure you don't put more than +5V in.