RE: [IBIS] Extracting V-T waveform data for the purpose of modeling a CMOS buffer

Hi Nam,

 

The four curves are necessary to indicate how "fast" the pull-up and
pull-down transistors turn on and off.  The turn on and turn off times are
different, so each transistor needs two curves.

 

I've attached a document that explains in detail, but in summary, you must
have all 4 curves if you want the best accuracy possible.  (Hopefully the
attachment comes through.)

 

Thanks,

Sam

 

 

  _____  

From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf
Of Nguyen, Duynam
Sent: Thursday, May 01, 2008 2:18 PM
To: ibis@server.eda.org
Subject: [IBIS] Extracting V-T waveform data for the purpose of modeling a
CMOS buffer

 

In section 3.2 of the 09/15/05 "IBIS MODELING COOKBOOK For IBIS Version 4.0"
document, it is stated,

". for each simulation corner, four V-T data sets are generally recommended.
Two waveforms - either featuring a load to ground or a relatively low
voltage - are generated for the buffer output switching low to high. The
other two waveforms - both featuring a load to Vcc or a relatively high
voltage - are generated for the buffer output switching high to low."

Why do we need two waveforms for each buffer output transition ? 

 

Thanks,

Nam    


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