- Joined Sep 7, 2021
In a 4-layer PCB, when to use both inner layers as ground planes? How do you decide if the inner layers should be power and ground, or both as ground?
I used to watch a lot of Phil's Lab videos. And as far as I understood, the power and ground as inner layers are not good for signal integrity.The main reason for going to 4 layers is to have two planes for traces that do not have to contend with power an GND routing.
So basically you are saying, for a 4-layer PCB stack up should be as shown below?The EM energy of the signals are in the PCB dielectric as it moves from point to point. I usually alternate signal/power and ground layers in a PCB to provide a conductive wave-guide for digital signals that act like RF in transmission lines as they move from place to place.
View attachment 281246
If you think electromagnetically instead of using static trace wire current flows the layered design is very intuitive.
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