[SI-LIST] Re: IBIS model.

Adam Tambone Wrote:

>
> Those are good points but I would like to add to the discussion regarding
> non-monotonicity and discontinuities in the I-V curves.  Non-
> monotonicities can and do exist in I-V curves. These non-monotonicities
can
> be valid and accurate representations of the device being modeled
> especially since they range over a broad voltage domain that goes beyond
> the recommended operating limits of the device i.e. -Vcc to 2Vcc.
> Simulators have difficulty processing the non-monotonicities, but this
does
> not make the curves invalid.
>
> Best Regards,
> Adam Tambone
>
Hi Adam:

Thanks for your comments, and as you stated non-monotonicities are allowed
and exist in I-V waveforms.

Many simulator programs sum the POWER Clamp and Pullup ( also GND Clamp
and Pulldown) currents to produce monotonic curves (for tristate buffers).

 I have also read that some simulators crash due to non-monotonicity
of the I-V curves.

In any case, when using an IBIS model (particularly for the first time) it
is advantageous to examine the I-V curves via methods described earlier.
Knowing the model (and the simulator) greatly helps to ascertain whether
the non-monotonicites are negligible,  or can cause significant simulation
inaccuracies.

An article by Bob Ross, "Practical Issues With IBIS Models", available on
the ANSI/EIA web site, contains a good discussion of the monotonicity topic.

Best Regards,

Abe Riazi
ServerWorks



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