[SI-LIST] Re: IBIS Model monotonocity and ICX and ibischk
- From: "Abhijit Mahajan" <amahajan@xxxxxxxxxxxx>
- To: tom@xxxxxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Mon, 11 Nov 2002 10:55:08 -0800
The summed curve is monotonic. I was told that ICX is checking them
individually!
But I guess I was misinformed.
Abhijit.
Tom Dagostino wrote:
>
> ICX only checks the summed IV curves, not them individually. Monotonicity
> is an issue because the lack of it can cause any simulator to either not
> converge or converge at the wrong solution.
>
> You need to fix the monotonicity issue.
>
> Tom Dagostino
> Device Modeling Division
> Teraspeed Consulting Group LLC
> 2926 SE Yamhill St.
> Portland, OR 97214
> (503) 430-1065
> tom@xxxxxxxxxxxxx
> http://www.teraspeed.com
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Abhijit Mahajan
> Sent: Monday, November 11, 2002 10:35 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] IBIS Model monotonocity and ICX and ibischk
>
> In the document IBIS Ver 3.2, on page 35 it is stated that (line 1)
> "The resulting difference table (after subtaction of both clamp
> currents from pullup and pulldown curves) can demonstrate a
> non-monotonic shape."
>
> Since this is indeed the case with most of the models I am
> generating, why does ICX complain about non-monotonicty?
>
> Also why does ibischk complain about non-monotonicty?
>
> What is the recommended course of action?
>
> I would assume ICX would sum the currents and then make a determination
> of the monotonocity.
>
> Thanks for your help.
>
> Abhijit.
>
> Larry Barnes wrote:
> >
> > 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
> >
>
> ------------------------------------------------------------------
> 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
------------------------------------------------------------------
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
Other related posts:
