Re: IBIS differential model questions

John,

Here are my thoughts on this. s2ibis2 or IBIS looks at a differential buffer
as if it was a single ended buffer. So only one leg of the buffer output is
modeled. Even the [Ramp] numbers are derived out of one single-ended output.

It uses the [Diff pin] keyword to indicate the other leg of the Diff buffer.
The simulators take info of the modeled single ended buffer and re-creates the
other leg of the Diff buffer(using [Diff pin]).

One problem here is the R_load gets tied to either Vdd or GND(based on test).
There is no true differential load. You can get by by using the V/T table data
and specifying V_fixture, R_fixture.

So, in summary, for a Diff buffer, you create ONE IBIS model(single-ended)and
use the [Diff pin] keyword to mention the other pin of the output.

Regards,
Syed
Cisco Systems, Inc

> From j_martin@qlc.com Mon Nov 23 14:30:37 1998
> X-SMAP-Received-From: outside
> From: John Martin <j_martin@qlc.com>
> To: "'ibis-users@eda.org'" <ibis-users@eda.org>
> Subject: IBIS differential model questions
> Date: Mon, 23 Nov 1998 14:26:19 -0800
>
> I am trying to build a differential IBIS model. I am not aware of a way to
> create a single IBIS model from a differential buffer which has two output
> pins and two independent voltage sources. It does not seem logical to
> create two IBIS models for one differential buffer, one for each output pin.
> Is there a way to create a single IBIS model for a differential I/O buffer
> using s2ibis2? I have read the section in the s2ibis2 manual that describes
> the differential pin list and it states that s2ibis2 does not process any of
> the information in that list, it simply copies it to the output file. I use
> s2ibis2 for Solaris to create IBIS models.
>
> Thanks,
> John Martin
> QLogic Corporation
>
Received on Tue Nov 24 13:30:52 1998