[SI-LIST] Re: Remove Ground underneath Differential signal is deserved or not?
- From: Ritchey Lee <leeritchey@xxxxxxxxxxxxx>
- To: scott@xxxxxxxxxxxxx
- Date: Wed, 31 Jul 2002 07:56:50 -0700
Scott,
If you just space the two traces in question the same as would be required to
make room for the guard traces, the cross talk will be the same as with the
guard traces and you don't need to add those extra structures. This is
relatively easy to show with a field solver.
In the bargain, there is no risk of creating unwanted resonant strucutres.
Lee
Scott McMorrow wrote:
> Lee,
>
> > What I show in my class is that guard traces are always LC networks that
> > resonate at some frequency and can and do turn into bandpass filters
> > at some
> > frequencies. I demonstrate this will actual failed circuits.
> >
> >
> This is exactly why Mike Conn and myself recommend stitching guard
> traces to ground at random intervals across the length. The average
> spacing of the via sites should be 1/10 of the wavelength of the fast
> signal frequency or equivalent risetime that will be present on this
> trace. These stitch vias to ground will eliminate the problems which
> you have alluded to. They are backed by extremely good analytical and
> experimental science.
>
> Best regards,
>
> Scott
>
> --
> Scott McMorrow
> Teraspeed Consulting Group LLC
> 2926 SE Yamhill St.
> Portland, OR 97214
> (503) 239-5536
> http://www.teraspeed.com
>
> --
> Scott McMorrow
> Teraspeed Consulting Group LLC
> 2926 SE Yamhill St.
> Portland, OR 97214
> (503) 239-5536
> http://www.teraspeed.com
>
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