Subject: RE: [IBIS-Users] Question about warning message
From: Ingraham, Andrew (Andrew.Ingraham@hp.com)
Date: Mon Nov 18 2002 - 15:31:58 PST
Maybe I'm the only person who feels this way, but in my opinion, there's
nothing wrong with a *table* that goes from -Vcc to +2Vcc.
But I agree that in many (if not most) cases it doesn't make sense to
force someone to measure currents over the full range, if they become
unreasonably large. Nor to extract such currents from SPICE using
s2ibis*.
In my opinion, the specification ought to make clear what to do in those
circumstances. Maybe what it needs, are additional comments about how
to create a full table when data points cannot be measured because the
chip would melt, or what to do when the simulated currents from SPICE
get unwieldy.
Some modern devices really need to have tables that go from -Vcc to
+2Vcc. There are some ICs that switch rail-to-rail and also lack one or
both clamping diodes, or that have clamp diodes that are so weak that
one could easily go a few volts into clamping without breaking a sweat.
Rather than letting model creators choose to use a narrower range, and
risk having too little data, I would rather force the model creators to
think about what they're doing, and come up with "best data" over the
full range even if some of it *might* not be used because the voltages
"never" go there. Anytime you say "never", someone could come up with a
case that contradicts your assumptions.
Regards,
Andy
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