Re: [SI-LIST] : effect of trace width on the performance

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From: Bill Owsley (owsley@cisco.com)
Date: Wed Nov 01 2000 - 07:50:10 PST


copper on the power planes and the current (power) level seems like a good
start.
ps. did the via size change ? did you track the power/ground into the pins
from vias attached to caps ?

At 07:04 PM 10/31/2000 -0800, Muhammad S. Sagarwala wrote:
>Patrick,
>
>The lines are single ended but the spacing betweent them is 2x, 3x or
>4x.(2x or greater) so
>I do not think cross talk is an issue.
>
>The edge rates on the boards are exactly the same.
>
>
>
>The problem I feel is because of "ground bounce"...I was wondering if the
>trace width and copper on power planes play a major
>part ?????
>
>Muhammad
>-----Original Message-----
>From: Zabinski, Patrick J. <zabinski.patrick@mayo.edu>
>To: msagarwa@san-jose.tt.slb.com <msagarwa@san-jose.tt.slb.com>;
>si-list@silab.eng.sun.com <si-list@silab.eng.sun.com>
>Date: Tuesday, October 31, 2000 6:54 PM
>Subject: RE: [SI-LIST] : effect of trace width on the performance
>
>
> >Muhammad,
> >
> >This alone would make me think the 7.5 mil wide trace board would
> >work better than the 9 mil wide trace board due to the lower crosstalk.
> >This assumes single-ended lines, but the opposite would be true
> >for differential lines. Are the lines differential or single ended?
> >
> >If this isn't it, my next best guess is the attenuation of the lines.
> >With cyanate ester, the loss tangent is quite low (around 0.001 if I
> >recall??), so I don't think you'll be running into much dielectric
> >loss at 400 MHz. However, the wider/thicker traces will have much
> >less loss at both DC and higher freqs than the narrower/thinner
> >traces (at least a factor of two better).
> >
> >Have you looked at the signal degradation differences between the
> >two boards? Are the edge rates on the two board different?
> >
> >If this isn't it, then I'm clueless.
> >
> >Pat
> >
> >>
> >> Exactly the same...
> >>
> >>
> >> >How about center-to-center pitch on routing tracks?
> >> >
> >> >>
> >> >>
> >> >> I am sorry Patrick,
> >> >>
> >> >> I forgot to mention ... the thickness of the boards is
> >> >> different. The one
> >> >> with 9 mil wide traces is thicker than the one
> >> >> with 7.5 mil wide traces.
> >> >>
> >> >> As regards other possibilities, the boards use the same
> >> >> dielectric material
> >> >> (Cynate Ester), the power planes on them
> >> >> are exactly the same, and the stackup is the same too and the
> >> >> placement of
> >> >> the decoupling caps is pretty much the same too
> >> >> (both the physical location and quantity)..
> >> >>
> >> >> Muhammad
> >>
> >
>
>
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----------------------------
Bill Owsley, owsley@cisco.com
919) 392-8341

TMBU Compliance
Cisco Systems
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