Subject: RE: [IBIS] IBIS Cataloging
From: Beal, Weston (weston_beal@mentorg.com)
Date: Mon Sep 30 2002 - 15:15:42 PDT
Steve,
Here are my opinions and experiences.
1) I found two ways of cataloging models that both work well. Both methods are based on directory structure. You can divide models by vendor or by function or both. I prefer to have a directory called "models" and in that directory have sub-directories based on functions like "cpu", "memory", "passive", etc. If you have a lot of memory models then you might have sub-directories in the "memory" directory for the different vendors or divided by memory sizes. As for the specific files, I like to put the file revision number in the file name and only keep the latest revision in the main model directories. I also like to have a duplicate directory structure called "beta_models" or something like that where I put models that are new and have not been verified. After they are cleaned up I move them into the main "models" directory structure.
2) Model verification comes mostly from experience and various tests on the actual model. For IBIS models I do a visual inspection of the text, run the latest ibischk and then parse it into my simulation tool (ICX). Then I set up a simple simulation test circuit to see if it simulates and if the results are what I expect. Expectations are based mostly on experience, so if it is a new technology, this is a bit more difficult to evaluate.
3) The tools use the models that you give them. If you want a specific model for a low ESR cap then you need to know how to model that. You can do it fairly well in standard IBIS 3.2 syntax. As for a file of all the resistors and capacitors, that would get uncontrollable pretty quickly. I just have file for all the resistors or capacitors that I need and then I add new ones as needed. If you'd like my small file in order to get started I can send it to you directly.
Regards,
Weston
-----Original Message-----
From: Drennan, Steven [mailto:steve.drennan@dy4.com]
Sent: Monday, September 30, 2002 12:41 PM
To: 'ibis@eda.org'
Subject: [IBIS] IBIS Cataloging
> Hi all,
>
> I'm new to the group but I have a few questions that will help me
> get up to speed quicker.
>
> 1) Does anybody know of a good method of cataloging IBIS models? We're
> using Mentor ICX (under UNIX) and although it has the ability to use
> filenames which do not need to conform to the 8.3 standard, is there a
> kind of adopted standard or best practice for nomenclature?
>
> 2) Considering it's possible for bad files to pass through parsers, is
> there anyone using a checklist to ensure a true gold model that contains
> all the necessary fields?
>
> 3a) Regarding resistors, capacitors, inductors, etc., what is the best way
> to properly model these in the circuit? For instance, not all 220uF caps
> are created equal but how does the simulator know the difference between
> an ultralow ESR cap vs. a regular cap? I'm just afraid if these devices
> are not modeled correctly, the simulator could tell me I need a larger
> capacitance value to eliminate noise but that's only because it doesn't
> realize I'm using a special LOW ESR cap.
> 3b) Is there such thing as a resistor.ibs model which contains all the
> various standard values in the different tolerances? If so, does something
> similar exist for caps?
>
> Thx.
> Steve
>
> ___________________________________
> Steve Drennan, B. Eng
> Components Specialist
> Dy 4 Systems
> Ph: 613.599.9199 x 5246
> Fx: 613.599.7777
>
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