Re: BIRD24 COMMENT

This raises an interesting point. How reliable is the value of C_comp itself?

Anyway I am not in favor any "implied" quantities associated with waveform tables. Every parasitc associated with that wave should be explicitly stated. So for example C_dut can include the effects of C_comp.

While I am at it I also want to raise another point regarding ky word Ramp.
That specification includes R_load. But there is no provisison for V_load.

If we look at the notes on Ramp rates there are situations in which V_load is
vendor specified and there is no place in IBIS models where thie information is
carried.

>
> To Committee:
>
> I only agree that there needs to be clarity in IBIS, but I do not support
> that C_comp = 0 is the mandated test condition for RAMP. I could accept
> that, but I definitely do not support such a mandate for Waveform Data.
> My concerns are these:
>
> (1) Removing the "effective" C_comp which is USUALLY not obvious cannot
> and should not be done to any Spice die model. That is a cumbersome
> process which can introduce unanticipated artifacts and other error. It
> is also one additional burden on top of a number of complicated processes
> such as those necessary for encoding Spice models for s2ibis conversions.
>
> (2) Responses based on measurements will always contain the effective
> "C_comp", and IBIS processes should accomodate that situation. So the
> problem is simple - either data based with C_comp included has to be
> "transformed" to no-C_comp data, or visa versa. Since C_comp cannot
> be removed for most cases, inclusion should be the default situation.
>
> (3) While I am not able to be specific at this time, I am convinced
> that the existence of C_comp in the extraction poses no insurmountable
> technical problem. I believe proper de-embedding techniques can be
> used, if they are necessary.
>
> (4) The Waveform Specification contains the purest form of untampered
> characterization data which is at the Pin if necessary, or at the Die if
> the packaging effects can be removed through simulation or die measurement.
> Under absolutely no condition should this (set of) reference waveforms
> be corrupted with tampering assumptions such as setting the C_comp to 0.
> While there may perhaps be inconveniences now, it is the wrong decision
> for future integrity of IBIS to conclude that such extractions or measurements
> which include C_comp can not be accurately dealt with in the future.
>
> Bob Ross,
> Interconnectix, Inc.
>
>
>
Received on Wed Dec 7 06:32:07 1994