(follow-up to Steve's comments on Q) Whatever happened to the technique that TDK came up with a couple years back where they were purposely increasing a capacitor's ESR to reduce Q (and thus the large peaks mentioned in this thread)? I remember seeing it a few DesignCons ago - it seemed like such a great idea... Jim. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of steve weir Sent: Thursday, November 06, 2008 8:07 AM To: Avtaar Singh Cc: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Power Integrity Question The simulators are reporting correctly. Your understanding of physics theory ( actually Calculus ) is incorrect. A convenient way to think about the impedance anywhere is as a result of the characteristic impedance and the Q. In the original case, the impedance significantly away from the original pole approximates the characteristic impedance. At each of the two peaks, when the impedance is reactive, Q > 1, and the peak impedance is substantially greater than the characteristic impedance. Therefore if you've got peaks at all the impedance will always be above the original curve surrounding each one. Steve. Avtaar Singh wrote: > Dear All: > I have a very basic Power Integrity question. > > Lets say a Power Delivery Network (PDN) has an impedance peak at 100MHz. I > add a capacitor that dips the impedance exactly at 100 MHz, and creates 2 > smaller peaks at, lets say, 20 MHz and 250 MHz. According to the theories of > Physics, these peaks should have their impedance value little bit lesser > than the impedance value of the PDN, at those 2 frequency points, before > this capacitor was added. But we do not always see that in simulation tools. > Sometimes we see that the 2 peaks that are formed have higher impedance than > the impedance that existed at those frequency points before this last > capacitor was added. This seems weird to me, because even though the ESR of > the caps should decide how sharp or blunt the Z peaks are, but an added Z in > parallel should always mean lesser impedance rather than more impedance. Can > someone please explain this paradox? > > Thanks for the kind guidance. > > Regards, > Avtaar Singh > > > ------------------------------------------------------------------ > 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 technical documents are available at: > http://www.si-list.net > > 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 > > > > -- Steve Weir Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 California office (866) 675-4630 Business (707) 780-1951 Fax Main office (401) 284-1827 Business (401) 284-1840 Fax Oregon office (503) 430-1065 Business (503) 430-1285 Fax http://www.teraspeed.com This e-mail contains proprietary and confidential intellectual property of Teraspeed Consulting Group LLC ------------------------------------------------------------------------ ------------------------------ Teraspeed(R) is the registered service mark of Teraspeed Consulting Group LLC ------------------------------------------------------------------ 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 technical documents are available at: http://www.si-list.net 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 technical documents are available at: http://www.si-list.net 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