[SI-LIST] Re: IBIS Model Quality (or lack thereof)


Hi Jeremy,
    What values do you use for fwf_tune and rwf_tune in your simulations with
Hspice?

Thanks
Jim Freeman

Jeremy Plunkett wrote:

> Todd,
> At a minimum, ServerWorks' IBIS models are validated prior to release by:
>
> 1) Syntax check using Hyperlynx Visual IBIS editor.
> 2) Correlation to the original spice deck waveforms using the hspice B
> element.  In the past, the degree of correlation has not been quantified
> because typically it is all-or-nothing;  either the waveforms are a 99%
> match point-for-point (inspected visually in Awaves), or there was some
> serious problem in the conversion that needs to be corrected.  Occasional=
> ly,
> there are correlation issues caused by limitations of the IBIS format or =
> the
> extraction process; in these cases we determine a work-around such as
> changing which model data is included in which curves, adding a submodel,
> etc.  When a standardized method of correlating the IBIS results to spice=
>  is
> determined by the IBIS qualification committee I would be happy to includ=
> e
> it in our correlation process, provided it can be accomplished either usi=
> ng
> hspice MEASURE functions such as DERIVATIVE, ERR, etc, or using a softwar=
> e
> utility that can import the waveforms from a text file.
>
> After the initial release, our models are converted to various other form=
> ats
> in-house and by our customers, which can sometimes bring out correlation
> issues between different simulators or problems with the model conversion
> processes.  Also, at some point after the initial release the models are
> correlated with silicon and corrected if necessary.
>
> Serverworks has the same situation that Adam Tambone mentioned in his
> posting, a large library of existing IBIS models(though not as large as
> Fairchild's), not all of which were generated or correlated to the same
> level of scrupulousness that we currently follow.  In our case most of th=
> ese
> parts are no longer being used in new designs, so fixing problems in the
> IBIS models is a low priority, however we will address any issues with an=
> y
> of our models as customers request it.
>
> To any customers who may be reading this: feel free to address any feedba=
> ck
> regarding ServerWorks' IBIS models directly to me (preferably privately, =
> not
> to the whole SI list).  However, please address requests to receive the
> models in the 1st place to our marketing dept.
>
> Jeremy
>
> |>--/\/\/--((((((((()--|>
>
> Jeremy Plunkett
> Signal Integrity Engineer
> ServerWorks Corp
> www.serverworks.com
>
> |>--/\/\/--((((((((()--|>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Todd Westerhoff
> Sent: Monday, March 25, 2002 12:59 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] IBIS Model Quality (or lack thereof)
>
> Hi all,
>
> We have been doing a lot of comparisons between IBIS and HSpice models
> lately, with a lot of less-than-satisfactory results.
>
> I have an open question for the semiconductor suppliers among us:
>
> What testing is performed after an IBIS model is created, to ensure that =
> the
> completed model behaves as expected?  I'm interested in responses from
> vendors that actually SIMULATE the IBIS model before distributing it for
> customer use.  It looks to me as though many of the models I've received
> were never used in a simulation before being released ...  and, as a
> potential customer, I find that quite disheartening.
>
> So the question is - what processes are being used to test IBIS models an=
> d
> ensure they function properly before their release to customers?
>
> As always, replies both on and off the list are greatly appreciated.
>
> Todd.
>
> Todd Westerhoff
> Signal Integrity Engineer
> Hammerhead Networks
> 5 Federal Street - Billerica, MA - 01821
> email:twester@xxxxxxxxxxx - ph: 978-671-5084
> =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=3D=3D=3D=3D=3D=3D=3D=3D=3D
>
> "I=92m starting With the man in the mirror
>  I=92m asking him to change his ways
>  And no message could have been any clearer
>  If you wanna make the world a better place
>  Take a look at yourself, and then make a change"
>
> - "Man in the Mirror", Michael Jackson
>
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