Re: [IBIS-Users] Sweep voltage listing query

Andrew,

You've posed a good question.  I think it cannot be answered in general, but 
only for a specific part.  The IBIS [model] structure may well be adequate 
in such situations, regardless of large changes in VCC.  The historical 
evidence is that IBIS provides a good model, despite repeated concerns over 
the years that there are problems just around the corner.  Of course, IBIS 
cannot do everything, but the question in a specific case can only be 
answered by measurements.

Christopher E. Reid
Chief Scientist and Founder
Pressando SI
9315 SW Lake Street
Tigard, OR 97223-6034
503-869-6703 (cell)
503-624-8159 (home)

----- Original Message ----- 
From: "Andrew Ingraham" <a.ingraham@ieee.org>
To: <ibis-users@server.eda.org>
Sent: Wednesday, April 19, 2006 5:21 AM
Subject: Re: [IBIS-Users] Sweep voltage listing query


> What would happen with a model of an IC with a very wide voltage range, 
> say
> for Vcc from 1.0 V to 3.6 V or more?
>
> For such a part, it may be better to create separate IBIS models for the
> different intended ranges; such as, one model for 1.5 V nominal, another 
> for
> 2.5 V, another for 3.3 V, etc.  But if you had a single model that worked
> well for the entire range (though it is debatable if you could make an
> accurate IBIS model to do this), what should it use for its sweep range?
> Probably not a Vcc in the middle of the range.
>
> Are devices tending to have greater relative Vcc voltage ranges?  Many 5 V
> parts were +/- 5% only.  Today's lower voltage parts have wider relative 
> Vcc
> ranges.  Perhaps IBIS needs to pay closer attention.
>
> Just a thought....
>
> Andy
>
>
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