Re: [IBIS-Users] ibischk4

From: Andrew Ingraham <a.ingraham@ieee.org>
Date: Thu Nov 04 2004 - 05:45:03 PST

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.

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.

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.

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 05:45:14 2004

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