Subject: typ outside min,max

From: Paul Gregory <[email-masked]>
Date: Fri, 14 Nov 97 9:50:41 MST

At first I thought this was a bug, that is to say, a 
defect in the IBIS models I had.  But now that I look
closer, it seems to be more prevalent than I would
have thought possible for a "bug".   Maybe it is
a feature. :)

What I have found is that "typ" data is outside the "min"
and "max" values. 

Consider this model fragment (greatly reduced for brevity) 
provided by a prominent silicon supplier:

[Pulldown]
|Voltage          I(typ)          I(min)          I(max)
|  [lines deleted for brevity]
-1.00E+00	-3.22E-02	-1.96E-02	-2.18E-02
-9.00E-01	-2.96E-02	-1.50E-02	-1.91E-02
-8.00E-01	-2.73E-02	-1.12E-02	-1.66E-02
-7.00E-01	-2.50E-02	-8.54E-03	-1.46E-02
-6.00E-01	-2.26E-02	-6.72E-03	-1.28E-02
-5.00E-01	-2.02E-02	-5.41E-03	-1.09E-02
-4.00E-01	-1.77E-02	-4.39E-03	-9.05E-03
-3.00E-01	-1.51E-02	-3.40E-03	-7.20E-03
-2.00E-01	-1.26E-02	-2.42E-03	-5.37E-03
-1.00E-01	-1.01E-02	-1.44E-03	-3.55E-03
0.00E+00	-4.67E-03	-4.60E-04	-1.43E-03
1.00E-01	1.82E-02	4.97E-04	1.33E-02  | typ out of range of min/max
2.00E-01	5.53E-02	1.43E-03	5.37E-02  | typ out of range of min/max
3.00E-01	9.70E-02	3.27E-03	9.92E-02
4.00E-01	1.41E-01	2.23E-02	1.44E-01
5.00E-01	1.85E-01	6.56E-02	1.95E-01
6.00E-01	2.29E-01	9.21E-02	2.50E-01
7.00E-01	2.72E-01	1.03E-01	3.01E-01
8.00E-01	3.12E-01	1.07E-01	3.49E-01
|  [lines deleted for brevity]

I expected that min and max represent the extremes of the
device behavior.  It seems that in some cases, it is not.
Should this be expected?  How is it explained?  

Should the model be changed to put the "extreme" value 
into the appropriate min or max column?

This does not seem to be a singular case either, I have 
observed this problem in more than 30 models from at 
least 6 suppliers.

Your comments?

 -- Paul Gregory

   phone: (208) 396-5086               USmail: Hewlett-Packard
     fax: (208) 396-4122                       M/S 143
   email: [email-masked]                  11311 Chinden Blvd.
                                               Boise, ID  83714

---

From: Fred Balistreri <[email-masked]>
Date: Fri, 14 Nov 1997 11:10:10 -0800

>    email: [email-masked]                  11311 Chinden Blvd.
Paul, I would tend to agee with you that it is a bit odd. However the
model should be looked at in the context of the whole curve, not
particuliar points. It is not the particuliar points that describe the
charactisitic but rather the slope of the points. In that respect the
typical curve should lie between the two extremes. It is my belief that
if you indeed plot the curves you would find that to be the case.
Occasional massive slope change within the curve may occur. Of course on
the other hand I have known to be wrong on occasion....at least thats
what my wife claims.

Best Regards,
-- 
Fred Balistreri
[email-masked]

http://www.apsimtech.com