[IBIS-Users] RE: [IBIS] C_comp Max < C_comp Min

All,

There is a very simple solution to this issue, please review the enclosed
draft {Model Corner] draft BIRD.

Walter

-----Original Message-----
From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Mirmak,
Michael
Sent: Monday, September 27, 2010 12:02 PM
To: Muranyi, Arpad; ibis@server.eda.org; ibis-users@server.eda.org
Subject: RE: [IBIS] C_comp Max < C_comp Min

One other item to note: not all device technologies associate a
numerically-smallest capacitance with the "fast/strong" process. Assuming
that CMOS rules universally apply would not have been appropriate, and IBIS
does not include any notations as to which process technology is used in the
design for the data presented. Without that information or some basic
ordering assumption, parsers have no means to confirm that the C_comp data
had been entered correctly.

As Arpad states, the only way to have enforceable parsing rules was to order
the C_comp from numerically-smallest to -largest, with the assumption that
the EDA tool would supply the missing information, likely from asking the
user (for example, the tool might inquire about the process used for the IC
in question).

Michael Mirmak

Intel Corp.

Chair, IBIS Open Forum

From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Muranyi,
Arpad
Sent: Monday, September 27, 2010 7:35 AM
To: ibis@server.eda.org; ibis-users@server.eda.org
Subject: RE: [IBIS] C_comp Max < C_comp Min

Fabio,

The reason you are getting that message is because the die capacitance

does not have a direct relationship with the fast/slow process corners

and when we wrote the IBIS specification we decided that it was best

to just put the small number into the min place and the big number into

the max place. It was expected that an EDA tool would allow the user

to try out all possible combinations between min/max curves and C_comp.

Arpad

========================================================================

  _____

From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Fabio
BRINA
Sent: Monday, September 27, 2010 7:12 AM
To: ibis@server.eda.org; ibis-users@server.eda.org
Subject: [IBIS] C_comp Max < C_comp Min

Hello Ibis experts,

 I'm working in CMOS tecnology;

 very often in the C_comp extraction I obtain the Min value bigger then Max
value:

 the values come from ac simulations in these conditions:

 C_comp Min value consider: Vcc Min, Process Min, Temp Max

 C_comp Max value consider: Vcc Max, Process Max, Temp Min

 The Ibis Check output is:

WARNING (line 76) -

    Model mod1: C_comp min value is not the smallest value listed

WARNING (line 76) -

    Model mod1: C_comp max value is not the largest value listed

Is that situation acceptable?

or I have to switch the Min Value with Max Value?

... suggestions are welcome !

Thank you,

Fabio

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