[SI-LIST] Re: What frequency are IBIS models good to?
- From: V S <for_si2003@xxxxxxxxx>
- To: si-list <si-list@xxxxxxxxxxxxx>
- Date: Wed, 15 Sep 2004 13:23:47 -0700 (PDT)
Venu,
1. On a lighter tone - notice the difference between
Muranyi and Muryani.
2. The ibis is not bad even upto 1 GHz. There is good
correlation in most of the cases till that frequency.
3. I beleive that there could have been less verbose
and more accurate method than 200 lines of VI for each
of the pull up, pull down, power clamp, ground clamp
and 100 lines for each of dV/dt. I have found that
spice models created with voltage control sources,
resitors are equally good and more intuitive to
understand and work with - rather that the verbose
black box ibis model.
4. I will suggest to always try to create your own
simpler spice model after "understanding" ibis model.
5. The ebd model is not well supported by some vendors
including SigXplorer.
6. Crosstalk is difficult to simulate with ibis / ebd
for package crosstalk.
7. I beleive that the major reason that ibis was
developed was to protect the IP. A Linux way would
have been more desirable rather than Microsof's way.
Spice could have done better job to provide models. It
would also have provided more intuitive understanding
of the models. .
8. This is not to attack Arpad's and Intel's ibis. But
to provide an insight - All good SI engineer like to
play with the driver and receiver model by creating
their own intuitive model to understand drive strength
variation, edge rate variation, package variation,
package crosstalk, die and package capacitance, etc.
9. Sometimes an optimal drive strength setting is
required for a particular driver and receiver. IBIS
will provide only extreme settings of drive strength.
An intuitive model will provide better understanding
of "what if" scenario.
VS
--- "Ummalaneni, Venu Babu (Venu)"
<venubabu@xxxxxxxxx> wrote:
>
> >hich are connected to the respective reference
> nodes that the
> corresponding IV curves are connected >to. So if
> the pullup IV curve is
> connected to the pullup reference, it can have its
> parallel=20
> >C_comp_pullup, and so on. This feature comes handy
> when someone is
> interested in power delivery=20
> >simulations.
>
> >One of the biggest drawback of C_comp for very high
> speed simulations
> is that it is a single and=20
> >constant number (aside from the 4-way splitting
> mentioned above).
> I.e., you can't=3D20 describe the >voltage or
> frequency dependence. For
> this reason, the IBIS model maker has to pick the
> best value >for C_comp
> that is valid for the frequency of operation and the
> signaling levels of
> the buffer. >This can be done, but may not be
> sufficient in every
> situation.
>
> >Arpad Muranyi
>
>
> Muryani,
>
> Do you mean to say this option of '4-way splitting
> mentioned above' is
> available in latest IBIS versions?
>
> Regards,
> Venu Babu.
>
>
>
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