AW: [IBIS-Users] ibischk4: ramp<->static curves

> Of course the Ramp data depends on the driver strength!
>
> I don't know what I was thinking yesterday ... I apparently wasn't.
> (Momentary brain fart. Nevermind!)
>
> I have had IBIS device models where the dV part of the [Ramp] data was
> nowhere near to agreeing with the I-V data.

I have sometimes models whene dV is obviosly taken with R_load=1e9 Ohm
(output with no load)

> It is also suspicious when a vendor gives you models with
> different I-V
> tables (or when they update a model and it has new I-V data),
> but precisely
> the same Ramp data. Obviously they took shortcuts, and the
> whole model is
> suspect.
>
> I'm surprised that this isn't verified by ibischk. It should be.

That is also my optinion! How could this be put inside?
I think it is much easier to talk to a vendor who gave me such
an erroneos ibisfile when I can tell him, that ibischk says
that there is an error inside.

> Katja, I would be careful about thinking that the ramp edge
> linear, all the
> way from 0 to 100%. It is probably not a bad assumption
> between 20 and 80%,
> but many waveforms have much lower slopes before 20% or after 80% ...
> especially beyond 10% and 90%. The first half cycle of a
> cosine wave isn't
> a bad approximation to some real signals into resistive loads.

Thank you for that information. Yes, I agree, that a totally
linear ramp looks not so good. Do you have physical or mathematical
basis for the cosine wave? I think I read something about a parabola.
And what about the signals into resistive loads? This is more an
e-function?

Regards,
Katja

> You might get by with a piecewise linear approximation where
> the 0-20% and
> 80-100% portions have much lower dv/dt, perhaps a third of
> that between 20
> and 80%.

> Regards,
> Andy
>
>
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Received on Thu Nov 4 06:52:05 2004