Re: gEDA-user: General ground/power plane design questions

[Steve Meier <smeier@alchemyresearch.com>]

Ok, my take on this is...

Putting the power plane and the ground plane next to each other does 
provide a hopefully uniform capcitor between power and ground across the 
entire board. Also, the transmission line impedence for traces running 
on one layer remain constant if the trace width remains constant. Extra 
layers of grounding can be added if you want to provide additional 
isolation between signals..


Signal layer
Ground
Power
Signal layer


Gives you both the power to ground capacitive coupling and uniform 
transmission line impedence for both layers. if you wanted to add a 
third signal layer you might as well add a second ground layer (board 
vendors would just add a dummy layer to have an even number of layers 
for board warpage reasons).


So then you get the stack up of

Signal
ground
power
signal
ground
signal

for each signal layer calculate the trace width for the desired 
impedence and....


Steve Meier



Karel Kulhavy wrote:

> On Wed, Oct 20, 2004 at 09:07:48AM -0700, Steve Meier wrote:
>  
> > Second, the power and ground planes should be inner layers. But for your 
> > frequencies I don't think you wil see many issues.
> >    
> Why?
>
> Cl<
>
>