FreeLists / si-list / [SI-LIST] Re: Interconnect Lumped Modelling

[Ed Sayre III <esayre3@xxxxxxxx>]

Strad,
   I recommend you look at Ron Poon's book "Computer Circuits Electrical 
Design" Chapter 5 and Appendix A5.1.  This will give you all the background 
and some applications that you need to formulate a lumped element t-line.

Regards
         -Ed Sayre

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                         "High Performance Engineering & Design"
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At 05:28 PM 8/5/2003 -0700, Stradlin Donald wrote:
>Hi Dima:
>
>So, does that mean that if I have a interconnect having a Td  = 300 ps and 
>a system rise time Tr =  31 ps, a lumped model can be created for it ? (as 
>per classical and conservative approach). However, some designers would 
>prefer using still slower rise-times....
>
>Actually I am a bit confused....So, Tr> Td/10 means that the propagation 
>delay is 10 times the rise time Tr. So, then how will it traverse the 
>interconnect length 10 times before it reaches its 90% value ? Wouldn't 
>that level be achieved at lesser than 1/10th the Td value already ?
>
>
>Dima Smolyansky <Dima.Smolyansky@xxxxxxxxxxxxxx> wrote:
>Strad,
>
>This analysis comes to us, I believe, from the basic physics of matter -
>more specifically, from the wave-particle duality of matter. There, an
>object is considered a wave or a particle depending on its size compared to
>the given wavelength. Lambda /10, specifically, is the rule there, where
>Lambda is the wavelength, and this is why the most rigorous rule people
>apply is Tr>Td/10.
>
>Specifically to your question: before the edge reached 90% of its value, the
>interconnect length should be traversed several times - about 10 times, if
>you apply the rule above directly. Most practical designers I talked to are
>content with smaller factors ( 2.5-4 is a typical ratio designers use), so
>that is how many times the interconnect length is traversed.
>
>For a faster rise time, the length of the interconnect that is considered
>lumped must decrease - for a large rise time, it will increase.
>
>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)
>www.tdasystems.com
>
>
>----- Original Message -----
>From: "Stradlin Donald"
>To:
>Sent: Tuesday, August 05, 2003 11:56 AM
>Subject: [SI-LIST] Interconnect Lumped Modelling
>
>
> > Hi All:
> >
> > I was just have a problem comprehend a certain theory practially and
>physically. Many theories suggest that a via/transmission line can be
>modelled as a lumped element if Tr>>Td where Tr = rise time of the pulse and
>Td = propagation delay of the length of via/transmission line.
> >
> > What might be the physical implications of this comparison ? Does it mean
>that before the edge reached 90% of it final value, the interconnect length
>should be traversed ?
> >
> > Is it a faster rise time or a larger rise time ?
> >
> > -Strad.
> >
> >
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