Lynne, there has been for many years an incorrect notion that bypass capacitors are not effective past their mounted SRF. This is at best a truism. The fact is that bypass capacitors work just fine decades beyond their mounted SRF. Istvan's DMB/DMI scheme that you will find detailed on his web site that you've referenced relies on this fact. At the beginning and end of the key issue in power delivery is inductance. If you are concerned with either or both cost and performance inductance of the components and interconnect is the limiting factor to both. Inductance drives basic impedance. Inductance drives Q in resonances. INDUCTANCE DRIVES THE NUMBER OF BYPASS CAPACITORS REQUIRED NO MATTER WHAT APPROACH IS USED FOR CAPACITOR VALUE SELECTION. While many pole networks can be very useful and Sigrity's Optimize PI(tm) customers are generally getting good results with that tool's approach, beware the rat hole of a many pole FD impedance plot: Those plots reflect voltage / current relations for circulating currents. This is Bruce's big caveat and one of the big reasons why he is so insistent on TD analysis. Best Regards, Steve. Lynne D. Green wrote: > Hi, Steve and Rajesh, > > Enough caps of one size will work, until your signal content goes too > far past the resonance frequency. > And yes, different packages have different parasitics and different > resonance freqs. > > Using a variety of (carefully selected) caps covers a wider frequency > range (several decades). > At the same time, this reduces the total number of caps needed, and > quite possibly total cost. > These days, there are EDA tools to make this easier. > > And I agree wholeheartedly with Lee that there are plenty of good > books out there. Istvan Novak's > home page lists several of them. http://www.electrical-integrity.com/ > > Lynne > > > steve weir wrote: >> And yet there are any number of boards and systems that have been >> built using mostly one capacitor value such as 0.1uF that work fine. >> >> Steve. >> >> Scooby Doo wrote: >>> Hi Lynne, >>> >>> This is what exactly what is wanted to ask. If the slew rate is >>> 1v/ns, then my 0.1uF capacitor value (designers blindly using value) >>> will not support due to existance inductive nature at that frequency. >>> >>> >>> So kindly give some reference / notes so that choosing right value. >>> >>> >>> >>> >>> --- On Mon, 3/15/10, Lynne D. Green <lgreen22@xxxxxxxxxxxxxx> wrote: >>> >>> >>> From: Lynne D. Green <lgreen22@xxxxxxxxxxxxxx> >>> Subject: [SI-LIST] Re: PDN related >>> To: "Scooby Doo" <si.scooby@xxxxxxxxx> >>> Cc: "SI LIST" <si-list@xxxxxxxxxxxxx> >>> Date: Monday, March 15, 2010, 5:20 PM >>> >>> >>> Depends on the frequency range where you need PDN clean. >>> If it is a wide range (generally true) then one would use >>> more than one value of capacitor. Remember, capacitor >>> impedance increases at high frequency due to inductive >>> package effects. >>> >>> Lynne >>> >>> >>> "IBIS training when you need it, where you need it." >>> >>> Dr. Lynne Green >>> Green Streak Programs >>> http://www.greenstreakprograms.com >>> 425-788-0412 >>> lgreen22@xxxxxxxxxxxxxx >>> >>> >>> Scooby Doo wrote: >>> >>>> Hi SI Experts, >>>> I have a question reg PDN. >>>> Suppose an FPGA has 100 I/O pins with 10 VCCO/Gnd pairs. So an >>>> average of 10 I/O pins for 1 VCCO/Gnd pair. Assume each I/O pin >>>> driving 10pf load. >>>> My qn is, to make the clean PDN, is it enough to provide 100pf of >>>> capacitor to each Vcc/Gnd pair? >>>> I am not convinced with blindly provinding 0.1uF cap to Vcco pins. >>>> kindly clarify. >>>> Thanks in advance for your valuable feedback. >>>> Rajesh >>>> >>>> >>> >>> >>> ------------------------------------------------------------------ >>> 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 >>> >>> 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 >>> >>> Old (prior to June 6, 2001) list archives are viewable at: >>> http://www.qsl.net/wb6tpu >>> >>> >>> >> >> > > > -- Steve Weir IPBLOX, LLC 150 N. Center St. #211 Reno, NV 89501 www.ipblox.com (775) 299-4236 Business (866) 675-4630 Toll-free (707) 780-1951 Fax ------------------------------------------------------------------ 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 Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu