In any real high speed/high power IC analysis, every FUB has different = loading, pipeline and switching pattern, different area of the clock = trees has different loading or even speed. None of the above has any = meaning or easy intepretation in frequency domain but makes a world of = difference in real life and in time domain. Frequency domain analysis = only gives you insight into where your potential package resonance is. = Beyond that you need a finer resolution into your FUB by FUB noise = budget based on time doamin analysis. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Ihsan Erdin Sent: Monday, December 04, 2006 6:20 PM To: thamiral@xxxxxxxxx Cc: si-list Subject: [SI-LIST] Re: Spectre S-parameter based modeling- Stability issues For the analysis of power delivery systems, I don't really see a big incentive to use a transient simulator as long as the linear load assumption holds. This applies to most practical cases. Usually the frequency domain solution will give enough information for the decoupling efficiency etc. A time domain response may be desired just to see the peak-to-peak noise level but then one can easily get it through IFFT as you put it. Regards Ihsan ------------------------------------------------------------------ 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 FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org 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