Re[2]: Process parameters

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To all,

The reason we originally wrote those guidelines in the "notes on data derivation
method" section was this:

Many times the process files describe the absolute worst cases which result in
very large variations. Most often such worst case conditions do not exist in
real life.

When you are working on a high speed system, you might not find a solution using
such models. This is why we choose to recommend to use the typical process with
temperature and supply variations only.

The extra guardbanding factor is there to provide for additional derating which
is to account for the process variations. You might ask why, if you could do
the same with using the best and worst case process files. These guardbanding
factors can be chosen so that your model would be more realistic than using the
absolute best and worst case process files.

For example, if your process files are made for 6 sigma variations, but you want
only 3 sigma models, you can come up with a derating factor to make 3 sigma
models using the typical process with voltage and temperature + derating factor.

Of course, if you have a 3 sigma process file, you could just use them to
convert to IBIS format without using the derating factor. It is really up to
you which method you chose. The whole point is that we want to provide the
means to be able to make realistic models for the devices.

Arpad Muranyi
Intel Corporation
=============================================================================
Hello Vipul,

Since we create our IBIS models from SPICE data, we would use
"typ", "min", "max" process parameters if we have them all.
Usually, the customers require us to have all the process-
variation corners in the model.

So I think the cookbook can include the case of "min", and "max"
as well as "typ".

Regards,

Hoang Nguyen
Mitsubishi Semiconductor America, Inc.

> From owner-ibis@server.vhdl.org Wed Jul 16 05:50:44 1997
> Date: Wed, 16 Jul 1997 03:48:15 -0500
> From: Vipul Singhal <vkumar@india.ti.com>
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> To: ibis-users@vhdl.org
> Cc: sram@india.ti.com, vkumar@india.ti.com, ngs@india.ti.com
> Subject: Process parameters
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> Hello all,
>
> I have a doubt regarding the method for obtaining the curves
> by simulation as outlined in IBIS COOKBOOK. The cookbook says ( under
> the section 3.3.1 : "OBTAINING CURVES BY SIMULATION - Simulation
> Specifics" ) that :
>
> "For both the rise/fall time and I-V curve measurements,
> use "typical" process parameters."
>
> "For CMOS:
> min = min VCC, max temperature, typ process parameters
> ---
> max = max VCC, min temperature, typ process parameters"
> ---
>
> Later it says that " To account for process variation, decrease the
> current values taken at min conditions, increase the current values
> taken at max, and derate the rise and fall time values by the
> appropriate percentages. "
>
> This seems to be a roundabout way of doing it. Why can't we
> directly use "typ" , "min" , and "max" process parameters, as
> appropriate, directly in the simulations ? For example, if SPICE is
> used for simulation, we can have three different SPICE models for
> transistors, corresponding to the process-variation corners. Why
> should "typical" be used in each case ?
>
> Regards,
> Vipul K. Singhal
> Texas Instruments
>
>

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Cc: sram@india.ti.com, ngs@india.ti.com
Subject: Re: Process parameters
To: ibis-users@vhdl.org, vkumar@india.ti.com
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From: hoang@msai.mea.com (Hoang Nguyen)
Date: Wed, 16 Jul 97 08:46:36 EDT
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