Re: Subtracting clamp curves from pull-up/down curves

Stephen,

Arpad's reply indicates that both clamp curves are indeed subtracted
to produce pullup and pulldown curves. I can verify the other side of
your question; that simulators (at least Cadence SPECCTRAQuest)
re-combine the curves as follows:

   low state: pulldown + powerclamp + groundclamp
  high state: pullup + powerclamp + groundclamp

So the clamps are never disabled (unless Submodel is used).

Mike LaBonte
Cadence

Stephen Nolan wrote:
>
> Hello IBIS gurus,
>
> When creating a model for a three-state device, it is necessary to subtract the
> clamp curves from the pull-up/down curves to avoid double counting, as the EDA
> tool adds the clamp-curves back in to the pull-up/down curves to obtain the
> devices output charactersitics in the enabled state. Right so far?
>
> The question is this, do you only subtract the corresponding clamp curve from
> the related pull-up/down curve, or do you subtract BOTH clamp curves from each
> pull-up/down curve?
>
> For example, if I am creating the pull-down curve, do I subtract only the
> ground-clamp curve, or do I subtract both the power-clamp and ground-clamp
> curves? Does the EDA tool add only the ground-clamp data back in, or does it add
> both curves back in?
>
> --
> Regards,
> Stephen M. Nolan
Received on Fri Jul 7 05:30:32 2000