[SI-LIST] Re: IBIS min, typ and max. values

  • From: "Lynne D. Green" <lgreen22@xxxxxxxxxxxxxx>
  • To: Hermann Ruckerbauer <hermann.ruckerbauer@xxxxxxxxxxxxx>
  • Date: Tue, 25 May 2010 15:06:35 -0700

Hello, Hermann,

Note that the "SPICE"  temperature is JUNCTION temperature, not ambient. 
IBIS [Temperature] is also junction temperature. The junction is hotter 
than ambient.

Since the TYP temperature is only 25C, it is likely that ambient was 
used instead of junction when creating the model. Generally, increasing 
TYP and HOT temperatures by 25C is used to account for self heating when 
simulating to create I/O models for IBIS.  COLD temperature is not adjusted.

Note the Max [Temperature] is higher in bipolar I/O and lower in CMOS I/O.

Hope this helps.

Lynne Green
Chair, IBIS Model Committee



Hermann Ruckerbauer wrote:
> Hello *,
>
> I hope somebody can help me with interpreting some things in an IBIS file
> I'm just working with an IBIS file where the min, typ, max values are
> arranged in the following way:
>
>                                        typ                
> min                 max
>
> C_comp                       0.284pF             0.409pF             0.264pF
> [Voltage Range]              1.200V              1.100V              1.300V
> [Temperature Range]          25                  125                 125
>
> The C_comp min is the largest value and the Temperature is in there
> twice with 125C.
> The same order is used for RAC and CAC for a terminator (largest value
> in the min column)
>
>
> e. g. in a Micron IBIS file is even some comment on having 0C as max.
> temperature :
>
> | Junction Temperature (Ambient temp is 25C typ, 85C min, 0C max)
> |                                       typ                 min        
>            max     
> [Temperature Range]        40.0               100.0                 0.0
>
> Regarding C_comp the Micron model lists it in the different order:
> |                                    typ                   
> min                     
> max                                                           
> C_comp                      2.466pF             2.316pF             2.616pF
>
> In the IBIS spec I found the comment that C_comp is independent of
> fabrication process and therefore to generate worst case it can make
> sense to use the largest C_comp for slow process ==> in the min column.
> Basically this makes sense to me, but does it then make sense to use the
> smalles C_comp value in the min column  ?
>
> So my questions would be:
> Is there any common usage of the min column regarding parameters like
> C_Comp, RAC, CAC (and maybe ohters) ?
> Usually I would expect low temperature for fast devices, so having 0C in
> the max column make sense, but does it make sense to have 125C in min
> and max column ?
>
> Any feedback is highly appreciated!
>
> Thanks and regards
>
> Hermann
>
> EKH - EyeKnowHow
> Hermann Ruckerbauer
> www.EyeKnowHow.de
> Hermann.Ruckerbauer@xxxxxxxxxxxxx
> Veilchenstrasse 1
> 94554 Moos
> Tel.: +49 (0)9938 / 902 083
> Mobile:       +49 (0)176  / 787 787 77
> Fax:  +49 (0)3212 / 121 9008
>
>
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