Subject: Re: How to deal with analog devices?

From: [email-masked] (Dan Aleksandrowicz)
Date: Fri, 17 Oct 1997 09:37:06 -0400 (EDT)

Hi Chen.

Your question is valid and important, however the answer depends on
your goal. If you are interested in analyzing all signals, including
analog signals and power plane/traces, you will need more than IBIS models.

IBIS modeling is mainly for analyzing digital signals between digital
components. Though most EDA tools support some level of discretes
and diodes, there might not be support for transistors in your
PCB signal integrity tool.

The solution for analog signal simulation lays in spice simulation.
As for mixing digital IC's IBIS models and "analog" components (i.e.
diodes, transistors and active bus tremination) the are spice tools
that can do it. But, getting the model for the above components to fit
an analog tool might be tricky.

I personally, in each SI project, take a hard look into the needs of
the system and define the signal list to be simulated. And then I can
define which component models are needed. Usually, I do not really need
analog models for signal integrity purposes.

Good luck.

                                Dan Aleksandrowicz
                                Engineering Solutions Specialist
                                e-mail: [email-masked]
                                39 Simon Street
                                Nashua, NH 03060

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From: Fawn Engelmann <[email-masked]>
Date: Fri, 17 Oct 1997 10:21:56 -0400 (EDT)

Hi Chen,

  Here is my take. There are three major classifications for
models to get into a board level signal integrity evaluation.

  First, IBIS models for buffer modelling.

  Second,  analog and jelly bean parts such as 
   resistors, capacitors, switches, etc. are
   typically modelled as very small spice like models.
   (Each vendor has their own little language parsers) 

  Third, connectors. Since IBIS support is supposedly on 
  the way, the signal integrity engine providers have 
  to currently offer their own language modelling support. 
  It is usually a primary RLC matrix with mutual inductance and 
  mutual capacitance specifications for the pins.

 Good question!

Thanks,
Fawn                                 _/    Fawn Engelmann
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