A tool from Cadence called SPECCTRAQuest with the Power Integrity option = will not only allow you to evaluate various capacitor types and = quantities, but also include their placement locations, their individual = mounted inductances and a model of the plane pair they are connected to. = The plane model includes skin effect and dielectric losses. It is not = only pretty cool to use, but very accurate and shares the same database = with the Allegro layout tool.=20 Check it out if you like. =20 Regards=20 Juergen Flamm -----Original Message----- From: Peterson, James F (FL51) [mailto:james.f.peterson@xxxxxxxxxxxxx]=20 Sent: Monday, August 04, 2003 12:19 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator Doug, In regards to :=20 <snip> 1. The reason we wrote the calculator in the first place was because we=20 couldn't figure out how to make the frequency response calculation for = an=20 arbitrary number of capacitors with arbitrary values, inductance and ESR = any other way. Then we figured others might have the same problem and = would=20 like access to the same tool. <snip> We've been having excellent results doing this very thing using PSPICE. We get complete control over ESR and ESL values, qty of caps, and their values.=20 We plot the results as ohms and freq (log) - which requires a little config... regards, Jim Peterson -----Original Message----- From: Doug Brooks [mailto:doug@xxxxxxxxxx] Sent: Monday, August 04, 2003 1:42 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator As the author of this calculator, I guess I'd like to throw in my 2 = cents=20 worth! 1. The reason we wrote the calculator in the first place was because we=20 couldn't figure out how to make the frequency response calculation for = an=20 arbitrary number of capacitors with arbitrary values, inductance and ESR = any other way. Then we figured others might have the same problem and = would=20 like access to the same tool. 2. The calculator helps demonstrate (as does our article) that one thing = that is REALLY desired for a smooth impedance response is a continuum of = capacitor self resonant frequencies (not necessarily simply capacitor=20 VALUES). A large number of caps with the same self resonant frequency = gives=20 you a single deep zero. Many self resonant frequencies spread over a = range=20 give you multiple zeros, spreading out the response much more = effectively.=20 MORE IMPORTANTLY, these zeros (and don't forget the poles in between) = REACT=20 with each other to provide a smoother response. The calculator helps you = demonstrate and prove that. 3. Along the way, the results from the calculator provided the evidence=20 (unexpected at the time) that moderate ESR is better than low ESR. The=20 reason is that while low ESRs give you very deep zeros, they also lead = to=20 very high peaks. Moderate ESR gives you an OVERALL better frequency response. 4. Finally, the calculator does not address the issue of placement. My=20 input on that question is this: Placement doesn't much matter EXCEPT for = (a) the electrons must be able to get where they are needed in time=20 (traveling at 6"/ns) and (b) loop areas (including those around and = through=20 caps) must be minimized for EMI reasons. Most people are aware of these=20 issues, and if they are taken care of, THEN placement is no longer an = issue. Hope this helps Doug Brooks > Doug Brooks' new book, "Signal Integrity Issues and Printed Circuit = Board=20 Design" has just been released by Prentice Hall. See details and = ordering=20 info at www.ultracad.com _________________________________________________________________________= ___ __ ------------------------------------------------------------------ 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: =20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages=20 Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =20 ------------------------------------------------------------------ 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: =20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages=20 Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =20 ------------------------------------------------------------------ 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