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" <stradlin_03@xxxxxxxxx> To: <si-list@xxxxxxxxxxxxx> 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. > > > --------------------------------- > Do you Yahoo!? > Yahoo! SiteBuilder - Free, easy-to-use web site design software > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu