Joel, you would scale the resistance and the number of resistors and/or total compensation networks to arrive at the inductance needed. The method is disclosed in Istvan's patents. Best Regards, Steve Joel Brown wrote: > Istvan, > > Just a few qusetions regarding your comments: > > By adding discrete resistors do you mean add them in series with normal low > ESR ceramic capacitors? > If 0402 packages are used for both would the inductance be sufficiently low? > I assume the higher ESR bypassing should be done as percentage of the total > bypassing and should not be used to bypass local IC power pins? > > Thanks - Joel > > > > -----Original Message----- > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On > Behalf Of Istvan Novak > Sent: Tuesday, March 11, 2008 6:04 AM > To: steve weir > Cc: Joel Brown; leeritchey@xxxxxxxxxxxxx; 'Scott McMorrow'; 'QU Perry'; > si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] Re: [!! SPAM] Re: 6 layers stackup > > Joel, > > Just a few late comments to the thread (I was on vacation): > > - setting the resistance to dampen resonances is a useful thing to reduce > worst-case transient noise and EMI risk. For regular MLCCs this usually > requires ESR values higher than what we get with a typical manufacturing > process today. > > - in ceramic capacitors the required resistance can be created either by a > smart internal construction (see the TDK announcement pointed out on the > thread), or by adding resistance externally such as printed resistors (such > as Sanmina's annual ring resistor) or by adding discrete resistor pieces > > - as it was mentioned, inductance is crucial: whether the resistance is > added inside the MLCC or externally, we should not add too much inductance > as it would defeat the purpose. Fortunately each of the above three > approaches can be implemented with sufficiently low inductance. > > - for implementation options and simulated measured results you can see some > of the published papers on the topic. See for instance: > "Overview of Some Options to Create Low-Q Controlled-ESR Bypass Capacitors" > and "History of Controlled-ESR Capacitors at SUN" in TecForum TF-MP3 > "Controlled-ESR Bypass Capacitors Have Arrived" on > http://home.att.net/~istvan.novak/papers.html > > Finally another comment on inductance: instead of setting the resistance to > the optimum value, sufficiently low overall inductance of the bypass > capacitors can also be used to reduce/eliminate resonances. This is the > rational (knowingly or unknowingly) behind the approach Charles mentioned > (sprinkling the board with a lot of capacitors) and this is > the reason why lower inductance parts are always a welcome help. > However, from a design point of view we need to keep in mind that using a > low cumulative inductance instead of the optimum resistance comes with a > price: either the low-inductance parts are more expensive, or the > low-inductance parts require more vias, or simply we need more parts. > Of course setting the resistance to the proper value has its own price tag > as well, so eventually the design engineer has to make the decision which > solution fits bets his/her requirements. Typically in low-density and > low-cost systems adding more capacitors works well; in high-density and/or > high-performance systems selecting PDN components with the proper resistance > becomes more attractive. > > Regards, > > Istvan novak > SUN Microsystems > > > steve weir wrote: > >> Joel, controlled / high ESR caps are rare birds. Istvan has been >> championing them for years nd some parts have been made. If you are >> prepared to buy 100,000,000 at a shot you might get somewhere w/ the >> manufacturers. But right now, most are running their lines to >> capacity w/ commodity parts. >> >> Regards, >> >> >> Steve. >> Joel Brown wrote: >> >> >>> While we are all talking about bypass caps, I just got done reading a >>> book by Bruce Archambeault called "PCB Design for Real-World EMI >>> Control". In the book there is a chapter on bypassing and it shows >>> measurements from actual test boards. In one case, a certain percentage >>> > of the caps are "high ESR" > >>> which seems to result in substantial damping (reduction) of the >>> > resonances. > >>> The high ESR caps are described as ceramic capacitors with a series >>> resistor built into the package, I have been unable to find such a >>> part. Has anybody found a benefit to this approach and a source for high >>> > ESR capacitors? > >>> Thanks - Joel >>> >>> >>> >>> >>> >>> >>> >> >> > > > ------------------------------------------------------------------ > 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 > > > > -- Steve Weir Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 California office (408) 884-3985 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