You need a model of the silicon that includes the on-die capacitance. You can try to obtain this, or if it is not available, then derive it from measurements. The complexity of the model that you construct depends on how much accuracy you need. You will still face the same challengess as others in the ATE business when dealing with the parallel bus structure of DRAM switching with very small rise and fall times, and the inductance of your probing interconnects. Steve. On 10/16/2011 2:25 AM, Cristian Gozzi wrote: > Hi SI members > I'm simulating DDR2 SSN for a Probe Card system > > for those that are not familiar with this application, Probe Card is an > hardware application to physical connect DIE pads/bumps at wafer level to > ATE system during Electric Wafer Sort > In my case Probe-Card is build by a vertical needles that touch DIE pads + > PCB > > During frequency domain analysis of my system, I got a strong PDN peak > impedance around 1GHz > This peak impedance was due to anti-resonance effect between PCB PDN system > and needle PWR parasitic effect > > so during time domain analysis I got a strong and unreasonable AC noises > also with only 2 switching DQ > > In my spice deck I only used IBIS model provided by silicon vendor and I > excluded RLC package effects, since my application is contacting directly > wafer. > > I think I should include chip power rail capacitance effect in order to > filter high freq noises. > > But my question is: which C and R value should I use? > > Is these value included in IBIS model? > > NOTE: consider that I had to reduce number of PWR needles used for HFSS > simulation, so I only selected those needles around my 8 DQ + 2 DQS > > So I think I should put a lower value of chip capacitance than total one > > Any comments from expert are more than welcome > > Thanks in advance > > Regards > Cris > > > ------------------------------------------------------------------ > 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