Thanks for all the answers ON and OFF-line. I was able to combine my two models into one. By analyzing the "active termination" model, I realized that VI curve of this active termination was in POWER Clamp and GND Clamp. So I just added this response to the more complex IO model (also in Power Clamp and GND Clamp), also removed the "active termination" model, and sim is OK now. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Ray Anderson Sent: Thursday, April 17, 2008 3:52 PM To: si-list@xxxxxxxxxxxxx Cc: Stephane Tremblay; Ray Anderson Subject: [SI-LIST] Re: IBIS question Stephane- Unless you zero out the values in the [Package] section of your IBIS model, those model parasitics will still be in the circuit when you put the parasitics external to your model in the main spice deck. (you may be accounting for the parasitics twice). Also, are you certain that there is no per-pin parasitic info in your IBIS model? If it is present it will be utilized and the min/max/typ numbers in the [Package] section will be ignored. (so even if you zeroed out the min/max/typ numbers you could still be double counting in this case). It is a little difficult to determine exactly what you are doing from the info given in your post, so if I'm barking up the wrong tree just ignore the suggestions :) -Ray Anderson Xilinx Inc. > -----Original Message----- > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] > On Behalf Of Stephane Tremblay > Sent: Thursday, April 17, 2008 12:26 PM > To: si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] IBIS question >=20 > Hi SI-Listers, >=20 >=20 > I am using a DDR IO buffer that has not been designed in-house. The > macro provider did provided us with an IBIS model for the Termination AND > another IBIS Model for the IO itself (since there is active termination on > DDR2). Since the two are connected on the same PAD at the die level, I did > the same on the simulation deck. By doing so, I got nasty sim results and > after investigation I realized that Package info was present on both IBIS > models. >=20 >=20 >=20 > As I think I am a smart engineer, I tried to decoupled the package info > from > the actual two IBIS models that I have, but I don't get the same results > if > I put the parasitic outside the IBIS vs. inside the IBIS. >=20 >=20 >=20 > Anyone has a clue why? >=20 >=20 >=20 > How do I get Package Parasitic outside the IBIS? Just setting RLC discrete > values outside did not reproduce the same sim. >=20 >=20 >=20 > Here is the Parasitic I need to separate from my Model: >=20 >=20 >=20 > [Package] >=20 > | variable typ min max >=20 > R_pkg 0.58 0.48 0.68 >=20 > L_pkg 5.80nH 4.10nH 7.50nH >=20 > C_pkg 0.58pF 0.51pF 0.65pF >=20 > | >=20 >=20 >=20 > Thanks, >=20 > Steph. >=20 ------------------------------------------------------------------ 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