Re: [IBIS-Users] VT Data Length Mismatch and Over Clocking

Hello Timothy,

I have also came across the same problem with one simulator where different
time lengths of V-T waveform gave me completely wrong results and just
making all tables equal by adding same last point has solved the problem.
Simulator vendor has accepted it as bug in tool.

Various simulators take care this issue internally by extending the last
points to make them equal.Thats why, somewhere it is recommended to have
same two last points in VT curve. I have checked the same model with 2-3
another simulators and all of them give correct results with different time
length.

Regards
Prabhat

On Wed, May 25, 2011 at 8:14 PM, Timothy Coyle
<tim.coyle@siconsultant.com>wrote:

> Hi,
>
> I'm starting to run across quite a few IBIS models that have different time
> lengths in the V-T waveforms even for corresponding loads. For example, a
> Rising Waveform with 50 Ohms to Ground may have a total time of 5ns but the
> equivalent Falling Waveform with 50 Ohms to Ground may have a total time of
> 10ns. So between the four different V-T waveforms they can all have a
> different total time length. All of the waveforms transition to a "steady
> state" but I'm wondering if this will cause potential problems in IBIS
> simulators?
>
>
>
> I know a lot of IBIS simulators say they can handle an over-clocked IBIS
> model but will this cause even more issues? I've also actually started to
> see a few models that say they must be over clocked to run properly
> (apparently model developer had issues getting VT waveform to reach steady
> state within bit time)
>
>
>
> I would think that the VT waveform total lengths should be matched based
> upon that they are used to define rise/fall transitions but clearly it all
> depends on how EDA IBIS simulator processes this data. It's difficult to do
> this type of correlation in multiple tools and without access to the
> original SPICE model but wanted to see if anyone else is running into this
> issue or can see potential issues with this type of model?
>
>
>
> Best,
>
>
>
> Timothy Coyle
>
> President
>
> Signal Consulting Group LLC
>
> 405 Western Ave #430
>
> South Portland, ME 04106
>
> Tel: 617.297.2566
>
> Email: tim.coyle@siconsultant.com
>
> Web: http://www.siconsultant.com
>
> SharkSim <http://www.sharksim.com/> - Signal Integrity IBIS Modeling
> Software
>
>
>
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