I've a 4 layer PCB in which I've to layout a power switching supply mixed with digital signal circuit.
My stack up is:
Top Layer: component and routing (power net and signals)
Internal plane 1: GND
Internal plane 2: +3V3
Bottom Layer: routing (power net and signals)
Now the question is: what's the better way to layout the GND internal plane?
I've thought of three possibilities:
use all the PCB area with GND plane
clear out both planes on the PCB area in which is present the power switching circuit and use the only what remains with GND
split GND planes and make a dedicated analog GND internal plane only for power switching circuit
I was thinking to proceed with solution 1), but I'm wondering if the power switching circuit may inject noise to the GND plane by coupling.
Is solution 1 OK? How should I modify it?