# RE: [SI-LIST] : Regarding plane splits

From: Larry Miller ([email protected])
Date: Tue Nov 14 2000 - 06:36:28 PST

How about inverse square law? That's the way return currents behave on
planes.

Larry Miller

> -----Original Message-----
> From: Zabinski, Patrick J. [SMTP:[email protected]]
> Sent: Saturday, November 11, 2000 5:01 AM
> To: [email protected]
> Subject: RE: [SI-LIST] : Regarding plane splits
>
> 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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