RE: [SI-LIST] : Best type of models, edge rates & load

Mellitz, Richard (richard.mellitz@intel.com)
Tue, 20 Jul 1999 21:53:50 -0700

Actually it would be more accurate to get the VT data with out even the
buffer capacitance. That raises some interesting testing problems when it
comes to determining real Tco. The problem is that the behavioral models are
most accurate when the Tco, VT, and IV is defined at the load of the target
design.
Richard Mellitz
Intel
-----Original Message-----
From: Mark Nass [mailto:markn@rccorp.com]
Sent: Tuesday, July 20, 1999 11:57 AM
To: si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : Best type of models, edge rates & load

We are not a foundry, just design the logic and rely on the foundry to
provide
HSPICE models. No magic with the models just use HSPICE models and vary the
process and temperature.

Weak models are > Slow process, high temp and low voltage
typical models are > typical process, nominal temp & voltage
Strong models are > Fast process, low temp and high voltage

I have no control over the accuracy of the HSPICE models, they come from
the
foundry. I am just curious if any knowledgeable people out there have
definite
ideas on which parameters are best for generating Tco values and IBIS models
that they have had good results with. I think I hear everybody agreeing that
40pf is not useful, so then my question is what is useful?

Mark

At 04:58 PM 7/20/99 -0500, you wrote:
>
>
>Mark Nass wrote:
>>
>> There has been some discussion recently about parameters of parts
>> specified into 40pf caps and accuracy of models. I generate this type
>> of data for our devices for our own use and our customers. So I am
>> curious as to what people think would be the optimal way to generate
>> Tco, Tsu, jitter parameters and IBIS models so that they would be
confident
>> they were getting exactly what they needed for signal integrity and
timing
>> analysis. Any feedback?
>>
>> Mark Nass
>
>
>Mark,
>
>Can your provide the SI community some insight on how you generate these
>parameters now. Specifically, do you take measurements on a number
>of different samples over temp/voltage ranges and with different loads?
>Are they SPICE derived? Do you specify a certain amount of 'cushion'
>in the parameters? This might be helpful to those of us who don't know
>how vendors derive the numbers.
>
>Thanks,
>David Haedge
>Raytheon
>
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