Dave,
A couple of other questions on the stackup: I see that 11 is a split
DVCC and 9 is a solid DVCC - could they be swapped? Also, Layer 4 is a
split DGND - do those grounds really need to be split? i.e., are they at
different potentials or will there really be ground currents that would
affect the circuits?
If you still have to route across the splits there are a couple of other
things you could look at; basically attempting to reduce the coupling
dependent on the split plane. Increase the differential coupling
between the traces - not much to do there other than keeping the spacing
tight. And, perhaps offset the trace layer towards the solid plane,
increasing the spacing to the split plane. An impedance calculator like
POLAR could give you the numbers.
Gary
--------------------------------
Gary A. Crowell Sr., P.E., CID+
www.linkedin.com\in\garycrowellsr
Micron Technology; Boise, ID
(208) 368-5325
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of David Baldwin
> Sent: Monday, November 24, 2008 3:09 PM
> To: [log in to unmask]
> Subject: Re: [TN] Stripline Traces and Plane Splits
>
> Well that's was my feeling too, that it would matter, that's why I
> was questioning it. but the 64K question is "How much does
> it matter?".
>
> Thanks to everyone for all of your responses!
>
> Dave
>
> At 08:17 AM 11/24/2008, you wrote:
> >David,
> >It really depends on how much signal degradation you can handle.
> >In most cases you would be ok but if it is a 6G data line
> with very low
> >tolerance then
> >you may have issues.
> >To answer your original question though, I disagree that
> since you are
> >coupled to one plane that the
> >integrity of the other plane does not matter. In reality,
> you are somewhat
> >coupled to both planes so it does matter.
> >Regards
> >Ken
> >
> >_____________________________________
> > Kenneth J. Wood
> >President
> >Saturn PCB Design, Inc. * <mailto:[log in to unmask]>
> >[log in to unmask]
> >2737 Bishop Lane * (407) 340-2668
> >Deltona, Fl 32725 fax: (386) 789-2765
> >www.saturnpcb.com
> >PCB_Design_new
> >
> >
> >
> >
> >
> >
> >
> >-----Original Message-----
> >From: TechNet [mailto:[log in to unmask]] On Behalf Of David Baldwin
> >Sent: Monday, November 24, 2008 9:36 AM
> >To: [log in to unmask]
> >Subject: [TN] Stripline Traces and Plane Splits
> >
> >Fellow Designers:
> >
> >I am designing a board with differential pairing in a stripline
> >configuration. One the bottom side is a solid ground plane. On the
> >top side is a split power plane.
> >
> >I was told that running traces across the splits is not a significant
> >problem as there is a solid ground plane on the other side for the
> >return currents to flow.
> >
> >Do you agree with this assessment and what has your personal
> >experience told you.
> >
> >Thanks in advance for your opinions and response.
> >
> >David Baldwin CID+
> >
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