Re: non-monotonicity

fabrizio zanella wrote:
>
> IBIS experts/users:
> I have a question regarding monotonicity of IBIS model curves. I have
> encountered some logic IBIS models (clock drivers) which pass the golden
> parser (with some warnings), but do not pass the IBIS parser within my
> simulator. The error I get is
> 'the sum of the maximum clamp curves and the pullup curve is non-monotonic
> at -0.5 volts'.
> I know for a fact that another simulator we have in house parsed these
> models. My question is, do some devices naturally have non-monotonic
> curves, and should an IBIS simulator accept this as a standard condition?
> Does anyone have experience modifying IBIS models to remove the
> non-monotonicity?

Some drivers really do have non-monotonic curves. We have some which
are protected against certain power states by having a line-operated
turnoff device on the driver gates, for instance; these have slope
reversals in their V/I curves.

-- 
D. C. Sessions
dc.sessions@vlsi.com