RE: ibis


Subject: RE: ibis
From: Dagostino, Tom (tom_dagostino@mentorg.com)
Date: Tue Sep 18 2001 - 15:58:02 PDT


Going from a released spec, one that a semiconductor manufacturer will send out will lead you to a much weaker model than the actual silicon. For example a typical part will have a Vol of 0.4V at 8 mA. In reality that driver will be 3 to 5 times stronger, 24 to 40 mA at 0.4V. The same applies to Voh. Most semiconductor datasheets do not specify rise and fall times so you will have to guess a transition time. You cannot just look at the underlying process used and make a guess because there may be structures in the output that control the slew rate. If you have rise and fall time specs in the datasheet they are likely to be accurate.

You will also need to know if there is a power clamp in the device.

For inputs the major items are what clamps and Ccomp. The rest of the data can be pulled from the datasheet.

Your best bet is to find another part from that manufacturer's process and copy that model assuming you can find one with the same output buffer used. If you have a sample you can make some measurements if you have power supplies, a high speed scope and some means of measuring the IV characteristics.

Tom Dagostino
Modeling Manager
Mentor Graphics Corp.
SAE
tom_dagostino@mentor.com
503-685-1613

-----Original Message-----
From: john austin [mailto:john_austinus@yahoo.com]
Sent: Tuesday, September 18, 2001 8:58 AM
To: Adam.Tambone@fairchildsemi.com
Cc: ibis-users@eda.org
Subject: Re: ibis

I have spec which specify the AC, DC requirement.
The specs contain V/I curves pullup & pulldown. Also,
the references curves of the pullup and pulldown.

I am looking to write an approximate behavioral model
for it. So I want to know what equations or portions
of the specs I need to pay attention to, to create V/I
tables, rising & falling waveforms.

I have some idea on how to proceed( based on other
IBIS models) but still I wanted to see a methodology
or guidelines already used by an expert.

Thanks

--- Adam.Tambone@fairchildsemi.com wrote:
>
> John, could you be more specific?
>
> Adam
>
>
>
>
>
>
> john austin <john_austinus@yahoo.com>@eda.org on
> 09/17/2001 07:11:34 PM
>
> Sent by: owner-ibis-users@eda.org
>
>
> To: ibis-users@eda.org
> cc:
>
> Subject: ibis
>
>
> If I want to create a behavioral model out of a
> spec.
> Could you please let me know what I should watch
> for?
> Also, if there is any documents or paper out there
> that facilitate the task?
>
> Thanks
>
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