Thinking about the switching in the IC is on the right path.... Let's go a little further.... think of the current needed by the IC to do all that switching. That current comes from the power supply rails... As such, one can think of the circuit starting with a source as DC (OK, this is an approximation, but good enough for right now)... followed by a number of low impedance transmission lines connected in series that represent the power delivery path (e.g. connector > pcb > vias > decoupling capacitors > package > silicon)... all the way to the switching device (FPGA, processor, etc.)... maybe more specifically, a switching load. This load will need to pull current through the transmission path at a rate relative to the requirements of all the transistors that are switching in the load. That rate can be expressed as a change in current relative to a change in time (di/dt).. This rate is a time domain response... (Which is supported by the electrical current in "bucket brigade" in the previous series transmission lines and decoupling capacitors)... IT all has to do with supporting the currents to the silicon. There are actually a lot of details I am skipping over... But, does this help?? BR Gus -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Taha Amiralli Sent: Monday, December 04, 2006 9:54 AM To: si-list Subject: [SI-LIST] Re: Spectre S-parameter based modeling- Stability issues Ihsan, Your comments are definitely correct. No matter how bad the S-parameter matrices are, with respect to passivity/causality, you will still get a frequency response and thus, an IFFT should do the trick. The thing is that I have read that spectre does use convolution when computing the time domain response from S-parameter matrices. So I guess the question then becomes, why would spectre fail to compute the transient response of a non passive S-parameter dataset, as is the case with Madhu? Bratfest, I definitely did not consider all those options... but I am still not sure why a transient response would be required... If the design is lets say an Integrated circuit, with lots of different loads, wouldn't it suffice to just find out what the max power levels required are and provide a power supply that is suited to the task? I guess I am still unsure of how a transient analysis would apply since the loading conditions are different depending on what the integrated circuit is doing at a certain moment in time. Thanks, Sincerely, Taha On 12/3/06, Dmitriev-Zdorov, Vladimir <vladimir_dmitriev-zdorov@xxxxxxxxxx> wrote: > > > Hi Madhu, > > We do have a tool that can solve the problem you describe, unless your > original touchstone files are of an extremely bad quality (in terms of > resolution, causality, passivity etc.) For example, if instead of > having > L2 norm of the matrix below one, it reaches 1.1...1.5, it is possible > to make the model passive without changing the dependences too much. > However, if the norm goes up to hundreds, this is less likely. > > Anyway, we may produce either passive/causal/smooth data in a form of > the touchstone file, re-sampled with sufficient resolution, or, in a > form of an equivalent SPICE-compatible circuit, whichever you prefer. > > Please contact off-line for more technical details. > > Vladimir > > > > ------------------------------ > > Msg: #5 in digest > Date: Sat, 02 Dec 2006 00:16:01 -0500 > From: Madhusudanan K Sampath <mkeezhve@xxxxxx> > Subject: [SI-LIST] Spectre S-parameter based modeling- Stability > issues > > Hi All,=20 > I am using n-port component in spectre to perform time domain > simulation using touchstone s-parameter files for power planes which > are obtained from measurement/full wave tools. In many cases, the > simulation explodes due to stability reasons. What are the possible > causes of this and how can one solve this issue. I think Spectre > n-port component uses convolution methods to perform time domain > simulation from frequency domain s-parameter data and hence are prone > to convergence issues. If so how does it enforce passivity in the > model. I verified the s-parameter matrix for eigenvalues and it proves > the data is not passive. I would like to compensate for passivity and > then re-try the time domain simulation. There are quite a few > interesting passivity enforcements techniques in literature by Dr. B. > Gustavsen and Dr S.G. Talocia . However they are applied on the > rational functions which are obtained by vector fitting the data. My > question is if I vector fit the data, enforce the passivity using > these techniques and then calculate the S-parameter matrix for each > frequency point from the passive rational function model. Will > spectre give stable results with this new data ?=20 > > Please share your ideas and views on this. Thanks in advance.=20 > > Madhu=20 > > =20 > > > > > ------------------------------ > > End of si-list Digest V6 #422 > ***************************** > > ------------------------------------------------------------------ > 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 > > > -- ------------------- Taha Amiralli thamiral [A] uwo [D] ca thamiral [A] gmail [D] com MESc Candidate 2007, Computer Engineering The University Of Western Ontario BESc, BSc. 2005, Computer Engineering & Computer Science The University Of Western Ontario --------------------------------------------------------------- ------------------------------------------------------------------ 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 ------------------------------------------------------------------ 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