Re: [IBIS-Users] IV clamp range

Hello, Vinayak,

You do not say which table exhibits a Crossing, or
at what voltage.
- A clamp table can have a crossing for V<0 when
the "clamping" is bipolar, while the drive is
CMOS. Physically, bipolar and CMOS exhibit
opposite dI/dTemp at fixed V. In this case, the
total current may also have a crossing.
- A clamp table can exhibit a crossing due to
numerical resolution when separating the clamp and
drive currents into their respective tables. The
total (summed) current usually does not show this
type of crossing.
- It is rare to see I-V crossings in the range 0
to Vcc.

It is strongly recommended for all I-V tables to
use the same voltage range (-Vcc to 2Vcc). In
your example, that would be -1.8V to +3.6V.

As a model maker, you could submit a model to the
IBIS Model Review Committee.
http://www.eda.org/ibis/home/support/support.htm

Cheers,
Lynne

Dr. Lynne Green
Chair, IBIS Model Review Committee

On 6/10/2011 12:00 AM, Ghatawade, Vinayak wrote:
>
> Hello,
>
> I have question reagarding the IV sweep ranges
> used for IBIS IV table generation.
>
> Cookbook does not have detailed sweep range for
> all corners specified explicitly.
>
> The reason that I am asking this question is we
> have IV table which has cross-overs for nom,
> strong and weak corners.
>
> In spice I see this behavior which is expected
> as per diode behavior since the corners are temp
> variable as well.
>
> Weak will turn on (125c) first and then followed
> by nom (25) and strong (-40c). This results in
> the crossover.
>
> Some customers are not willing to have these
> crossover (not sure why?). But I feel since this
> is real behavior you should see the same
>
> reflected in the ibis model.
>
> Do you see a reason why IV crossovers are not
> allowed (recommended). I did not see any
> checklist or parser giving out any warning
> /error due this this.
>
> Going back to the sweep voltage range when I see
> this crossover in spice (I sweep voltages as
> mentioned in cookbook) and report the strong,
> weak to fit in the
>
> typical range voltage axis in the ibis model.
>
> Ex 1.8V IO below is the numbers that I use for
> IV sweep range.
>
> Sweep range that I use for typ
>
> -1.8 to 3.6
>
> Min/weak will be
>
> -1.962 to 3.428
>
> Max/strong will be
>
> -1.602 to 3.798
>
> Thanks
>
> vinayak
>
>
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