Subject: IBIS Questions???

From: "nijjar" <[email-masked]>
Date: Mon, 17 Apr 95 18:10:58

Hello,
          I have couple questions regarding IBIS modeling. I would
          appreciate if someone could help me to get going.

          First question I have is about 'Model Libraries'. I have
          about 70-80 ICs to be modeled. For all these ICs, there are
          only 6-7 different I/O pin models. So, I'm wondering if its
          possible to have one big file which has only the pin models.
          The IBIS model for each IC then references this big file for
          the pin model information.  It would save me some disk
          space. It would also give me much less frequent headaches,
          when comes the library maintenance.

          The other question I have is about C_comp (silicon die
          capacitance). Is it different than Input/output
          pin capacitance given in the Data Books? Is it same as
          gate/diffusion capacitance?

          Thanks in advance,
          Gurjit S. Nijjar
          Integrated Circuit Systems, Inc.
          (408)925-9431

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From: [email-masked] ( Bob Ross)
Date: Tue, 18 Apr 95 10:49 PDT

Gurjit:

To be IBIS compatible, it is required to have all the models that are 
called by a pin model to reside in the same file.  It is permissible to for
the file to contain models that are not referenced by the pin models, but
not visa-versa.  Since you are dealing with only 6 or 7 I/O pin models,
you should be able to add them to the pin model file or else split the
pin model file into several files, each containing the same set of I/O pin
models.  

Regarding C_comp, most data books describe the Cin and Cout paramters as the
device or die capacitance.  This is the same as C_comp.  Actually, C_comp
can be viewed as an effective or equivalent die capacitance which is the
summation of all possible contributions including diffusion capacitances
and metalization.  Based on theory, the actual capacitance can vary with
voltage and operating conditions, but an effective fixed capacitance such as
found in data books or obtained by using some extraction method provides the
C_comp for IBIS models.

Bob Ross,
Interconnectix, Inc.
(503) 603-2523

> To: [email-masked]
> Cc: [email-masked]
> Subject: IBIS Questions???
> Status: RO