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

  • From: Hermann Ruckerbauer <hermann.ruckerbauer@xxxxxxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Thu, 27 May 2010 01:59:24 +0200

Hello Arpad,
thanks for the feedback. In this case  I guess I have missunderstood the
part below your quote from the spec:
C_comp is considered an independent variable.  This is because C_comp
| includes bonding pad capacitance, which does not necessarily track |
fabrication process variations.  The conservative approach to using IBIS
| data will associate large C_comp values with slow, weak models, and the
| small C_comp values with fast, strong models.
|

So I interpreted this as: Put the large C_comp value into the min Column
(and I also interpreted Toms and Steves feedback this way), but
according your statement the lowes C_comp should be in the min column
and the EDA tool need to select the max value when I simulate with slow
settings.
But re-reading Steves response he just mentioned I should use the
largest C_Comp for worst case slow corner simulation, but he did not
mention how I should do this.
I might need do select the setting of C_comp manually if simulate slow
corner and the IBIS file has the lowest C_Comp value in the min column ... 

But this then opens again my original questions:
Does it make sense to put the large C_com value in the min Columen ? (or
the highest Temp in the Min column)
As I have seen IBIS files with different methodologies on the
arrangement of C_Comp I don't really think that my EDA tool will decide
correctly which C_comp to select ...

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


schrieb Muranyi, Arpad:
> Hermann,
>
> I am not sure where you got the idea from that the IBIS spec
> says "one can place the largest value in the min Column in
> order to have the worst slow case covered".  If you look in
> Section 9 of the specification, you will find the following:
>
> | The "min" and "max" columns for all remaining keywords and
> subparameters
> | will contain the smallest and largest magnitude values. This applies
> to the
> | [Model] subparameter C_comp as well even if the correlation to the
> voltage,
> | temperature, and process variations are known because information
> about such
> | correlation is not available in all cases.
>
> Thanks,
>
> Arpad
> ==============================================================
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Hermann Ruckerbauer
> Sent: Wednesday, May 26, 2010 10:29 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: IBIS min, typ and max. values
>
> Hello Sudhanshu,
> that's interesting.
> In this case the spec and the IBIS cookbook mention it differently ...
> The cookbook mentiones to use the same order (smallest value in the min
> column) and let the tool decide, while the Spec mentiones, that one can
> place the largest value in the min Column in order to have the worst
> slow case covered ...
>
> Any feedback from the tool vendors how they implemented this selection ?
>
> 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
>
>
> schrieb Sudhanshu SINGH:
>   
>> Hello All,
>>
>> Reagrding c_comp as put previously in this mail, I have a query that,
>> why c_comp values extracted in typ, min or max conditions are not put
>> respectively in same typ, min or max columns in IBIS.
>>
>>
>> As Section 5.1.3.1 of cookbook ver4 says:
>>
>> Note that when constructing the IBIS file the numerically largest
>>     
> value of
>   
>> C_comp is listed as the "max" value while the numerically smallest
>>     
> value of
>   
>> C_comp is listed as the "min" value. C_comp min and max values do not
>> necessarily correlate with the min and max conditions under which the
>>     
> I-V
>   
>> and switching data was gathered. The actual association of C_comp
>>     
> corner
>   
>> values with simulation corners is performed at the tool level.
>>
>>
>> Thanks and Regards,
>> Sudhanshu
>>
>> -----Original Message-----
>> From: si-list-bounce@xxxxxxxxxxxxx
>>     
> [mailto:si-list-bounce@xxxxxxxxxxxxx] On
>   
>> Behalf Of Hermann Ruckerbauer
>> Sent: Wednesday, May 26, 2010 2:23 PM
>> To: Lynne D. Green
>> Cc: si-list@xxxxxxxxxxxxx
>> Subject: [SI-LIST] Re: IBIS min, typ and max. values
>>
>> Thanks to all who replied (that fast).
>> I just love the List and everybody sharing his knowhnow there !!!!
>>
>> BTW: Happy Birthday!!!!
>>
>> 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
>>
>>
>> schrieb Lynne D. Green:
>>   
>>     
>>> 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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