In such an application where you have enough plane capacitance and the location of the dicretes don't matter then why have them at all? I presume that one is trying to lower/control the overall impedance of the power system. If so then the number of discretes and location may matter. What is your opionion Lee? Best Regards, Lee Ritchey wrote: > > If capacitors make a difference at these frequencies, it means that you > have inadequate plane capacitance. You likely, also have excessive ripple > which will manifest itself as occasional instabilities. Specifically, when > a large data bus switches from all 0 to all 1. > > When you fix this with a good plane capacitor, the location of discretes > won't matter. > > Lee > > Lee Ritchey > leeritchey@xxxxxxxxxxxxx > Why Wait? Move to EarthLink. > > > [Original Message] > > From: Zhangkun <zhang_kun@xxxxxxxxxx> > > To: <si-list@xxxxxxxxxxxxx> > > Date: 8/4/2003 8:57:58 PM > > Subject: [SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator > > > > Dear All: > > > > In our simulation and measurement, we found that power noise of at least > 400MHz could be decoupled by discrete caps. The placement DOES matter the > impedance of PDS. The current problem is the anti-resonance between > different kinds of caps. > > > > Best Regards > > > > Zhangkun > > 2003.08.05 > > ----- Original Message ----- > > From: "Juergen Flamm" <jflamm@xxxxxxxxxxx> > > To: <si-list@xxxxxxxxxxxxx> > > Sent: Tuesday, August 05, 2003 3:44 AM > > Subject: [SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator > > > > > > > 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 > > > > > > > > ------------------------------------------------------------------ > > 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 > -- Fred Balistreri fred@xxxxxxxxxxxxx http://www.apsimtech.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: //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