FreeLists / si-list / [SI-LIST] Re: Signals crossing power plane split

["Loyer, Jeff" <jeff.loyer@xxxxxxxxx>]

Similar scenarios have been discussed in this forum - I think you'll
find quite a bit of info. in the archives.  The subject fields were:
"Impact of gap on stripline"
"Current return path"
"Reference Plane"

Jeff Loyer



-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Fabrizio Zanella
Sent: Wednesday, December 03, 2003 1:31 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Signals crossing power plane split


I have a few nets which are routed on a dual stripline layer, on a
multilayer board, and these nets are referenced to ground on one side
and a power plane with several split voltages on the other side. The
signal layer, SIG LYR2, is 3 mils from the VCC plane and 8 mils from the
ground plane.  The VCC plane is part of a BC layer, so it is 2 mils from
a ground plane on the other side of the signals on SIG LYR2.  Both VCC
and GND planes are 1.3 mils thick. =20
                          =20
      ____________________________________  GND LYR1         =20
                     ________       SIG LYR1
GND LYR1 to VCC LYR =3D 11 mils  =20

                    _________      SIG LYR2
SIG LYR2 to VCC LYR =3D 3 mils

    ____________      gap     ________________VCC LYR        VCC LYR to
GND LYR2 =3D 2 mils

   _____________________________________  GND LYR2
=20
The nets in question, on SIG LYR2, have to cross gaps in the VCC layer.
My question is, will the return current for these signals use GND LYR2
as a reference to get across the splits?

Thanks,

Fabrizio Zanella
Principal Hardware Design Engineer
Broadbus Technologies
fzanella@xxxxxxxxxxxx
=20
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