Assume you have a four layer board.
- Signal
- GND
- Dielectric
- VDD
- Signal
And you having a track in the 4:th layer. Suddenly you're using a via to go through the 4:th layer to 1:st layer.
Question
The reference plane for the 4:th layer is the 3:rd plane, which has a potential lager than GND volt. The VDD don't have to be 3V3 volt, it can be voltage for DDR memory as well.
But once you're routing your track from 4:th layer to 1:st, you're also changing the reference plane to GND, which is now 2:nd layer.
Should you place a copper plane at the 2:nd layer which has the same voltage potential as the 3:rd layer?
Update:
This is one example where I add a copper plane and asign VDD onto it. Now the stack is
Signal/GND GND GND Signal/GND
Perhaps this is not good at all? I need to get the capacitor-effect? The C144 is a 10 uF capacitor.
If I cover the second layer with the first layer like this.
