RE: clarification on IBIS min and max values

> I need some clarification on IBIS min and max values for CMOS circuits.
> For CMOS circuits, a high temperature is associated with "min" or
> slow-weak behaviour. Similarly, a low temperature is associated with
> "max" or fast-strong behaviour.
>
> However, the package parasitics (L,R and C) have the biggest values
> corresponding to "max" and smallest values corresponding to "min". Why
> aren't the smallest parasitics values associated with "max" or fast-strong
> behaviour instead?
 
A simulator does not need to set all parameters to their "min" values", or
"max" values, simultaneously. It can mix-and-match any way it sees fit.

It is assumed that the package values are not (or might not be) correlated
with anything else ... that it is entirely reasonable to pair "max" L_pkg
with both "min" and "max" drive strengths, etc. Both results may be
interesting to look at. A given simulator might look at both, or maybe only
one.

For example, a fast-strong driver and min L might produce minimum delay, but
a fast-strong driver and max L might produce maximum overshoot and ringing,
which might even cause maximum delay (due to ringback).

The IBIS exception is Temperature, where it is assumed that the temperature
IS correlated with driver strength. In this one case, "min" is whatever
temperature causes weakest drivers (high temperature if it is CMOS).

Andy

 
Received on Tue Nov 14 12:56:45 2000