Xilei, you can improve frequency response flatness with equalization of=20 one form or another. A shunt inductor / resistor combination can drop=20 the low frequency response to compensate for what the shunt capacitance=20 takes from the high frequency. It is important that the parameters are=20 controlled well enough that you can adequately damp the response at the=20 parallel resonance, or you will suffer big amplitude and phase shifts. Steve. Xilei Liu wrote: > Dave, > =20 > Will a varistor (shunt), inductor (series) help for this case? I don't= have any simulator to try. Thanks. > =20 > Regards, > Celine > Date: Thu, 15 Nov 2007 20:03:42 -0700> From: telegrapher9@gmai= l.com> To: jeetshah@xxxxxxxxx> Subject: [SI-LIST] Re: On-Chip Parasitic C= & its effect on R> CC: si-list@xxxxxxxxxxxxx> > Jitesh,> > does your chi= p have ODT? I ran a frequency domain sim using an> electronic Smith Chart= and adding an inductor didn't help. I'm able to> rapidly sweep various c= omponent values and did not obtain good return> loss until adding some se= ries resistance. Of course to keep the delay> low and not attentuate the = signal too much this value I limited to 25> ohms. Here is the model:> > 1= 2 ps, 50 ohm t-line. 50 ohm ODT shunt. 25 ohms series resistor. 400> fF s= hunt, 5 ohm series, 400 fF shunt.> > This was modeled single-ended. Your = application is differential, is> it? Also, the 25 ohm series resistor iso= lates the ESD circuitry. Not> good but this might lead to some more insig= ht into this matching> problem. The ESD circuitry and driver/receiver are= modeled as the 400> fF, 5 ohm, 400 fF.> >=20 > Dave Cuthbert> Consultant> > > On Nov 15, 2007 5:48 PM, Jitesh Shah <j= eetshah@xxxxxxxxx> wrote:> > Hi Everybody,> >> > I am designing a flip ch= ip package for multi-Gbps> > SerDes (6.25Gbps & above) where as a stand a= lone> > package, I am able to optimize the flip-chip> > interconnect stru= cture to meet the return loss> > specification of 10dB for up to 2x the f= undamental> > switching frequency i.e., 10GHz.> >> > But due to the on-ch= ip parasitic capacitance (~800fF)> > associated with the transmit driver = circuitry and the> > ESD structures around it, the chip+package return lo= ss> > degrades significantly and violates the 10dB spec.> >> > I was hopi= ng to design an inductor on package to> > compensate for this cap and to = bring the odd-mode Z to> > 50Ohms but in the TDR profile, the impedance> = > discontinuity created by the chip C and the package> > impedance discon= tinuity occur at different times. So> > regardless of what structural opt= imization I do> > on-package, it does not i > mprove the overall> > chip+package RL performance.> >> > Can anybody s= hed some light on this or point me to> > some resources I can use.> >> > = Regards,> >> > Jitesh Shah> > Advanced Package Design> > IDT> >> >> >> >>= > ______________________________________________________________________= ______________> > Be a better sports nut! Let your teams follow you> > wi= th Yahoo Mobile. Try it now. http://mobile.yahoo.com/sports;_ylt=3DAt9_qD= KvtAbMuh1G1SQtBI7ntAcJ> > -----------------------------------------------= -------------------> > To unsubscribe from si-list:> > si-list-request@fr= eelists.org with 'unsubscribe' in the Subject field> >> > or to administe= r your membership from a web page, go to:> > //www.freelists.org/web= page/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:> > http:/= /www.freelists.org/archives/si-list> > or at=20 > 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@fre= elists.org with 'unsubscribe' in the Subject field> > or to administer yo= ur membership from a web page, go to:> //www.freelists.org/webpage/s= i-list> > For help:> si-list-request@xxxxxxxxxxxxx with 'help' in the Sub= ject field> > > List technical documents are available at:> http://www.si= -list.net> > List archives are viewable at: > //www.freelists.org/ar= chives/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> >=20 > _________________________________________________________________ > Feel like a local wherever you go. > http://www.backofmyhand.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 technical documents are available at: > http://www.si-list.net > > 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 > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > =20 > > > > =20 --=20 Steve Weir Teraspeed Consulting Group LLC=20 121 North River Drive=20 Narragansett, RI 02882=20 California office (408) 884-3985 Business (707) 780-1951 Fax Main office (401) 284-1827 Business=20 (401) 284-1840 Fax=20 Oregon office (503) 430-1065 Business (503) 430-1285 Fax http://www.teraspeed.com This e-mail contains proprietary and confidential intellectual property o= f 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