[SOLVED] Need helo how to split a dual power plane

[mfd]

Hello,

I'm new at this. I need to find out the proper way to split a layer with dual power planes. I want to do a 4 layer PCB:
L1 - signal traces
L2 - Split layer with 5V and 3.0V planes
L3 - ground
L4 - signal traces.

The components using 3.3 or 3 are all over the board so the 2 options I was thinking are:
1- Do 2 comb shaped power planes interleaving each other. This is would be a kind of a symmetrical layout.
2 -Do it like connecting traces from components' pads to pads using wide traces.

Or if there's a better way to do it I would appreciate to know.

Thanks in advance. Regards,

Mario

 

[samym]

hi,
let me know which tool you are using allegro or PADS?

 

[marce]

Are the signals high speed or do they have fast rise times?
As I learnt recently, this can cause both signal integrity and EMC problems. The best way for power distribution is a layer for each voltage but this isn't always possible, this then means split power planes! As you are going to have a signal layer next to a split power plane layer, these signals will be referenced to this layer, and crossing a split is not good.
If you have or can get hold of H. Ott 'Electomagnetic Compatability Engineering' part 16.3 Return Path Discontinuities.
As to distributing the power, it is hard to comment without knowing the topography of your layout, current requirements, switching requirements etc. There is a lot of info coming out about "power supply integrity", its worth having a look around the web for info on it.

 

[samym]

hi,

if you are going with split means make sure there is in no highspeed signals under split in L1..if you can't do like that means put one power in L1 or L4 or L1 & L4...l2 should be solid no split

 

[Mattylad]

AFAIK - Swap L2 & L3 around so GND is at the inner top

 

[mfd]

Thanks everyone for your help