RE: [SI-LIST] : Regarding plane splits

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From: Zabinski, Patrick J. (zabinski.patrick@mayo.edu)
Date: Sat Nov 11 2000 - 05:00:59 PST


Aloke,

As I mentioned in a recent posting, there are conditions in which
routing stripline in a configuration you describe sees no effects
from the split. More specifically, if your trace layer is "closer"
to the solid ground plane than the split power planes, then the
solid plane has "more" of an influence on the trace. As such, you
will "less" of a discontinuity from the split. I've tested this
in the lab under several conditions, and I believe this to be true.

However, the reason I used "'s in the above statements is that I
haven't taken my experiments far along enough to be able to provide
any guidance as to how "close" is "close enough" to reduce the
discontinuity effects to the point where your system can tolerate
them.

In what I call a 50/50 case where the stripline layer is centered
vertically in the stackup such that the distance to the solid ground
plane is the same as the distance to the split plane, you will notice
the discontinuities.

Pat

>
> Hello all,
> I had a doubt regarding plane splits:
>
> In the stackup, if there is a power plane on one side of the signal
> layer and a ground plane on the other side of the signal
> layer(symmetric
> stripline config), and if the ground plane is a solid ground plane
> having no discontinuities, then can I have splits in the
> power plane and
> run traces over the splits? Is the ground plane alone not
> sufficient to
> provide paths for return currents?
>
> With regards,
> Aloke
>
>
>
>

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