> Hi,  I hope someone can help me out here.  I'm looking for suggestions on
> ways to quite down traces that we know are going to be noise generators.  If
> using a 6 layer board...what is the best stack up?  Should power and ground
> planes always be kept next to each other for optimum capacitive performance?
> Which layer should these noisy lines be kept on?  Any help?

Controlling the trace impedance is more important than keeping the
planes together, so you will end up with 2 signal layers between
the planes (sig, plane, sig, sig, plane, sig) on a 6-layer pcb.
If your "noisy" traces are long, using the inner signal layers may
provide some shielding, but adding vias can increase the noise.
Make sure the noisy lines are properly terminated (if possible),
make sure they have decoupling near any vias, make sure they
don't cross plane splits, and adjust the width if neccesary for the
proper impedance.


Dave Farthing
Gordian Design Services

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