From: Mike LaBonte ([email protected])
Date: Tue Jan 02 2001 - 05:36:58 PST
Dennis,
Your stackups have 5 and 4 signal layers, respectively. When you say
you are using the same Gerber files, doesn't that mean the layer routes
are the same, with only the via padstacks changing? How is the "extra"
signal layer used?
Mike LaBonte
Dennis Yarak wrote:
>
> I haven't been following threads recently (too busy) but I do have a mildly
> interesting result to report in re: split planes.
>
> After discussions with our EMI experts we decided to do two different stack
> ups with the same gerber files. This is a 10 layer/50 ohm board with
> s-g-s-s-g-pslit-psplit-s-g-s, and the alternative was
> s-g-s-psplit-g-psplit-s-g-s.
>
> The first stack optimized for signal return path (only one signal layer sees
> the power split, and layer 8 was routed carefully) while the second
> optimized for VDD decoupling to ground.
>
> Even though this was as controlled an experiment for EMI as we could do, the
> specifics of the situation determine whether the result would be applicable
> in general. We didn't have the luxury of trying to reroute layer 3 to be
> better behaved across the new plane splits it sees in the alternate stack,
> for example.
>
> We found the first stack was a few dB better pretty much across the board.
>
> Dennis Yarak
>
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