Hi Steve, Please correct me if I am wrong as I am new to this. I would like to know more about this correlation. I am suspecting this due to either the termination modeling or the waveform models. What kind of Termination models do you have on IBIS?. Do your IO Pad cell have both Common mode as well the differential terminations? Could you please share the IBIS model details (Especially the Clamp Curve data, if the pad cell inside the chip has common mode terminations too). Do the waveforms capture the step (due to reflection) in the IBIS models? Regards, elechi On Tue, Jun 8, 2010 at 7:52 PM, Santangelo, Steven <SSantangelo@xxxxxxxxxxxx > wrote: > Hi All, > > > I'm trying to correlate some lab measurements to my simulations in > Cadence PCB SI (SpectraQuest). I have a 400MHz unidirectional LVDS > interface between two Xilinx devices that is terminated in 100ohms > inside one of the devices. My lab measurements show a pretty good > reflection occurring on the rising and falling edges of the waveform. > I'm trying to determine if this is being caused by the ball to I/O pad > trace length in the package (plus my BGA breakout). My simulation only > shows a slight bend in the waveform rather than the non monotonic ring > that I see in the lab. The bend does correlate well time wise (location > on the edge) with the lab measurement. I don't really know much about > the limitations of IBIS models so I'm wondering if some of the > discrepancy could be due to that. > > > > FYI: I'm using the models that Xilinx "ibiswriter" puts out. The > rise/fall times of the waveforms are in the neighborhood of 300pS. > > > > Thanks > > > Steve > > > > > ------------------------------------------------------------------ > 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