At 3X the package cut-off: 1. You are well-past resonance that occurs just below the cut-off. 2. The amount of energy transferred is typically down 20dB. The impedance of the PCB above this point will have very little impact on the power delivery in the IC package. You could simulate to a higher frequency but with little improvement in result accuracy or actionable information. You could also simulate only to a lower frequency, but with rapidly increasing uncertainty near what is usually the highest, or close to the highest impedance seen by the die. Steve. On 5/18/2011 4:12 AM, Rajan Hansa wrote: > Thanks Steve for being always prompt in reply !! > Can you please explain how you have got this magical figure, 3 X > highest package cut-off frequency ? Why It's not 2 X or 1 X ?? > Rajan > > On Wed, May 18, 2011 at 4:21 PM, steve weir <weirsi@xxxxxxxxxx > <mailto:weirsi@xxxxxxxxxx>> wrote: > > If you are concerned only with power delivery then simulate to 3X the > highest package cut-off frequency of any device you are concerned with > that is attached to a given power rail. > > Steve. > On 5/18/2011 3:44 AM, Rajan Hansa wrote: > > Hello All, > > > > > > I have got a PCB database of one Ethernet Board and I have to > extract > > s-parameter for all power plane from voltage regulator to power > pin of > > chip package. The Board database includes all decap. > > > > > > > > As we know extraction time is directly related with maximum > frequency So > > while setting maximum frequency for s-parameter extraction, I am bit > > confused, I would like to know that do I need to set knee > frequency ( Fknee > > = 0.35/Trise) as maximum frequency OR for board level simulation we > > shouldn?t care knee frequency. > > > > > > > > As per my understanding, package inductance won?t allow very > high frequency > > component (switching current component which depends on Trise > !!) to travel > > to board from chip so voltage regulator in board will never see > those high > > switching current so I shouldn't simulate/extract s-parameter > till knee > > frequency. > > > > > > > > What?s expert view on this ? > > > > > > > > Rgds, > > > > Rajan > > > > ------------------------------------------------------------------ > > To unsubscribe from si-list: > > si-list-request@xxxxxxxxxxxxx > <mailto: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 > <mailto:si-list-request@xxxxxxxxxxxxx> with 'help' in the Subject > field > > > > > > List technical documents are available at: > > http://www.si-list.net <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 <http://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 > <mailto: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 > <mailto:si-list-request@xxxxxxxxxxxxx> with 'help' in the Subject > field > > > List technical documents are available at: > http://www.si-list.net <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