I agree with all of the preceding discussion. Additionally BIRD 73.4 = was incorporated into IBIS 4.0. This provides the functionality for = modeling pre-emphasis or fallback models. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Lawrence C. Barnes Principal Signal Integrity Engineer QLogic Corporation 2660 Laguna Hills Drive Aliso Viejo, CA 92656 larry.barnes@xxxxxxxxxx -----Original Message----- From: Scott McMorrow [mailto:scott@xxxxxxxxxxxxx] Sent: Wednesday, November 06, 2002 12:25 PM To: fabrizioz@xxxxxxxxxxxx Cc: mohammad.ali@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: IBIS model for CML differential buffers Fabrizio and Mohammad, CML buffers up to 3.125 Gbps can and have been modeled in IBIS=20 effectively. At DesignCon 2002, Chris Brewster of SiQual presented a=20 paper on buffer correlation between Hspice and Cadence SpecctraQuest.=20 There were no issues with driver output model correlation. All=20 correlation issues were concerned with lossy trace model discrepancies=20 between SpecctraQuest and Hspice. I believe that these Cadence issues=20 have now been resolved. As differential buffers become faster, it is=20 actually easier to model them in IBIS, since these drivers have to be=20 operating mostly in the linear region in order to operate at these=20 extreme speeds and edge rates. IBIS models are always best and most=20 faithful when extracted from linear drivers. Also, since the buffers=20 are operating differentially, the influence of SSO is minimized.=20 Current starvation effects and pre-driver modulation effects are=20 greatly reduced over their single-ended counterparts. Any issues in=20 simulation at these speeds is usually due to improper modeling of=20 packages, vias, connectors, return-paths, and losses in the system. =20 (As a side note, my research, simulations and measurements indicate that = via-coupling in the driver BGA breakout region and in the region of the=20 first connector insertion tend to have the most detremental effect on=20 these high-speed signals. These effects are often not modeled at all,=20 or are modeled inappropriately or incorrectly by Signal Integrity=20 simulators and extractors and/or engineers performing simualtion and=20 modeling of differential systems.) Having said this, it is not "fun" to extract these IBIS models and it=20 can be quite time consuming to do so. A more sane approach that I often = use is to create a synthetic behavorial driver in hspice using voltage=20 sources (or current sources), input waveshaping filters, a VCVS for=20 output swing adjustment and a resistor to approximate the output=20 impedance of the device, and then perform an optimization of the circuit = to reproduce the original spice output waveform of the driver. This=20 usually takes less time than performing a differential IBIS model=20 extraction and is incredibly fast in simulation. In either case, preemphasis is not easily modeled. It is possible to=20 use multistage driver models in IBIS to perform pre-emphasis=20 simulation. This works quite well, since pre-emphasis is generally an=20 increase in the output signal swing on the leading edge of a bit pattern = and can be approximated nicely by a timed multistage pulse. =20 Several companies have the ability to model these differential devices:=20 SiSoft, SiQual, Mentor and Teraspeed. We can actually extract the=20 models from measurment, and have done so in the past for some 10 Gbps=20 devices. In some cases, the silicon vendor prefers IBIS measurement=20 based models to Hspice models, because of the increased accuracy of the=20 measurements. We have modeled devices with risetimes in the 30 to 50 ps = range. best regards, Scott --=20 Scott McMorrow Teraspeed Consulting Group LLC 2926 SE Yamhill St. Portland, OR 97214 (503) 239-5536 http://www.teraspeed.com Fabrizio Zanella wrote: >Mohammad, I don't believe modeling CML differential buffers in the IBIS >format can be done yet. The speeds are extremely fast, 2.5 to = 3.125Gbs, >with sub-100ps risetimes, so the accuracy of transistor models is >required. Also just about all CML I/O have various levels of = transmitter >pre-emphasis and/or receiver equalization, which is not handled by the >IBIS spec today. >My suggestion is to use spice models. >Regards, > >Fabrizio Zanella >Signal Integrity Engineer >Broadbus Technologies >fabrizioz@xxxxxxxxxxxx > >-----Original Message----- >From: si-list-bounce@xxxxxxxxxxxxx = [mailto:si-list-bounce@xxxxxxxxxxxxx] >On Behalf Of Mohammad Ali >Sent: Wednesday, November 06, 2002 7:22 AM >To: si-list@xxxxxxxxxxxxx >Subject: [SI-LIST] IBIS model for CML differential buffers > > >Dear SI members, > >Can anybody point me to some resource links (any article, paper or >presentations) where I can find some helpful information on how to >accurately generate IBIS models (pullup, pulldown, PC, GC etc.) for >CML (current mode logic) differential buffers? So far I have=20 >succefully created models for TTL, CMOS and LVDS buffers operating=20 >upto 622 Mb/s range. IBIS official websites and some EDA vendors >websites and discussion pages have some model development topics,=20 >but none of them about CML technology.=20 > >Hazem Hegazy from Mentor Graphics and Arpad Muranyi from Intel=20 >delivered excellent articles and presentations on LVDS modeling. I >am looking for something like those but on CML technologies. > >Any helpful hints or links would be highly appreciated. Thanks. > >-Mohammad Ali > > =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 archives are viewable at: =20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages=20 Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =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 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