Re: Ibis model for differential input from rkarthik@lsil.com

Karthik: I had a similar problem a few months ago and I asked Alan Glaser for help.
For your info, attached below is copy of my original question and his reply. The way
I got around it is exactly what he suggested. I had to make a virtual inverter in
front of the differential input to provide the out-of-phase signal. Since timing
(prop delay) is not utilized in the IBIS model, it makes no difference in the final
output. I am not sure if things have changed since. If it has, I certainly would
like to know about it.

Jeff Chu
Digital Equipment Corp.
77 Reed Road
Hudson, MA 01749
(508)568-4197
(508)568-5195 fax
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Hi

I have problems when running ibis on a differential input receiver.

I am not quite sure of how to set my <filename>.s2i input file correct, especially
the
usage of [Diff Pin] option in correlation with [Pin] mapping.

could someone address my concerns? / mail me a example ibis model with differential
inputs.

Thanks in advance.
Regards,
Karthik.

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From: CRL::"awglaser@eos.ncsu.edu" 25-FEB-1997 11:48:57.33
To: rock::chu
CC: awglaser@eos.ncsu.edu (Alan Wolfram Glaser)
Subj: Re: your mail

> Alan: Please help me with the following on your spice to ibis conversion program.
> How do you specify differential inputs together with an enable pin in the pin list?
 The
> six valid input pin formats do not include the option of differential inputs. In
this
> particular circuit I have, I need to control the two differential inputs to make
the output
> swing. How do I do it?
>
> Thank you very much for your help
> Jeff Chu
> Digital Equipment Corp.
> 77 Reed Rpad
> Hudson, MA
> 01749
> (508)568-4197
> (508)568-5195 fax

Jeff:

Unfortunately, s2ibis2 doesn't have an automatic way to control two
inputs. The only thing I can suggest it to let s2ibis2 create the input
files, edit them by hand to insert the source for the second input,
delete the output files (*.out) then re-run s2ibis2. (It will use the
SPICE files that already exist.)

Hope this helps.

Regards,

-- 
Alan Glaser                         "It's not a competition,
ECE Dept.                            it's just a mint..." - K
North Carolina State University
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