I need to do a PCB layout where I have one digital signal that has relatively short rise/fall times crossing a slot in a GND plane. I know that this should not be done, because the signal return current should always flow directly under the PCB trace. But in this PCB desing, I have no other option.
So I thought it could be a good thing to place a capacitor (e.g. 1nF) across the GND plane slot. Then the signal return current can flow through that capacitor.
Does anyone have experience with such a kind of bridge capacitor across a GND slot? Is it possible to avoid radiation and/or reflection with this kind of setup? (I have to add that this PCB is extremely sensitive to EMI).
I know this is a very general question. I'm just seeking general advice from the cummunity.
Best Answer
That will provide a signal return path, but will also AC connect your two grounds.
Usually when I see split grounds, it's to prevent noise from one ground from affecting the other one. You should take a look at what's near to the connection point and avoid having any noisy or sensitive circuits in the area.
Personally, I like to keep grounds together and try to route signals to localize noise--which also helps EMC--but every design is different, so you have to make your own call.