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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