Subject: Re: [IBIS-Users] C_comp value in IBIS model
From: Kim Helliwell (kimgh@apple.com)
Date: Fri Aug 01 2003 - 14:44:50 PDT
If the waveforms already include the effects of C_comp, putting
the C_comp value in the IBIS model will double-count the effect
of C_comp, which is probably not what you want.
I feel certain that the right thing to do is re-run the spice sims
with C_comp removed from the simulations, and put the correct
typ/min/max values of C_comp directly in the IBIS model
If I were your customer trying to use this model, I'd be really unhappy
to find that C_comp was (silently) being double counted. And I'd
be suspicious of your model if C_comp were 0 with no explanation.
At the very least, if you don't want to re-run things, you should set
C_comp to 0 but put in a comment that the reason it's zero is that
the effects of C_comp are included in the rising/falling waveforms.
But this is definitely a distant second-best, in my opinion.
Kim
On Friday, August 1, 2003, at 02:13 PM, Abril, Giovanni wrote:
> Hello IBIS gurus,
>
> I've created an IBIS model using a spice netlist from the vendor, and
> I'm wondering what to do with C_comp. My rising and falling waveforms
> include the effect of C_comp, but what should I put in the IBIS
> model? I have a spec sheet that says min C_comp is 2.8pF, max is
> 10pF. Currently I have 5.0pF for typ, 2.8pF min and 10pF max.
>
> Thanks,
>
> Giovanni
>
>
Kim Helliwell
Apple Computer
kimgh@apple.com
408 974 9936
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