[SI-LIST] Re: TDR Resolution
- From: steve weir <weirsp@xxxxxxxxxx>
- To: Dima.Smolyansky@xxxxxxxxxxxxxx, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 17 Jan 2005 09:52:23 -0800
Dima, as usual you bring up a good point. If the idea was to find a
microscopic needle in a very large haystack, I agree that isn't going to
happen. I don't know if my suggestion to limit based on the application is
helpful to Merrick or not.
Regards,
Steve
At 09:31 AM 1/17/2005 -0800, Dima Smolyansky wrote:
>STeve,
>
>If one is trying to resolve a tiny via discontinuinity in the middle of 40
>inch backplane, it is not going to happen, because the rise time will slow
>down substantially and the via will not show up, even if your initial rise
>time is 2X or 3X or 5X the actual signal rise time. On the other hand, if
>your actual signal is slower than the TDR analysis rise time will not see
>this discontinuity either. So, this discontinuity does not exist for your
>signal for all practical purposes. An interesting effect, and 34 see it all
>of the time.
>
>So, the most practical approach would be to use the TDR rise time that is
>slightly faster than the actual signal rise time if you are working with a
>specific application (slightly faster to have a bit of the confidence
>guardband). However, this is not what Merrick is after, and I think Kipp's
>analysis is most appropriate for his question.
>
>This issue is discussed in pretty much every single TDA systems appnote - we
>have a nice collection of those at www.tdasystems.com/support.
>
>Thanks,
>
>===================
>Dima Smolyansky
>TDA Systems, Inc.
>4000 Kruse Way Place
>Bldg. 2, Suite 300
>Lake Oswego, OR 97035
>(503) 246-2272
>(503) 246-2282 (fax)
>
>IConnect version 3.1 has been released!
>http://www.tdasystems.com/press/pressroom/pressreleases.shtml
>----- Original Message -----
>From: "steve weir" <weirsp@xxxxxxxxxx>
>To: <mmoeller@xxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
>Sent: Monday, January 17, 2005 8:50 AM
>Subject: [SI-LIST] Re: TDR Resolution
>
>
> > As Tr approaches Tf across a feature, the amplitude of the dip or peak
> > will
> > shrink and the width will spread out. Ie, the pulse integrates the
> > feature
> > with neighboring geometry. As a practical matter I would suggest using a
> > TDR Tr that is 2X to 3X, but not more as fast as the application risetime
> > you intend to support.
> >
> > Steve.
> > At 10:21 AM 1/17/2005 -0600, Moeller, Merrick wrote:
> >>Experts,
> >> I am in the process of running a simulation
> >>In order to resolve signal path discontinuities. Is there a
> >>Rule of thumb that would give the minimum rise time signal
> >>To resolve a min length discontinuity?
> >>Regards,
> >>Merrick
> >>
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