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

  • From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
  • To: <si-list@xxxxxxxxxxxxx>
  • Date: Thu, 27 May 2010 06:47:50 -0700

Hermann,

The problem with that sentence that you quoted is that it
doesn't say clearly how or where that "association" is done.
It actually doesn't refer to where you put the big or
small values in the IBIS file.  It refers to how the simulator
uses these values.  In other words, for slow simulations it
suggests that the simulator should pick the value from the
max location in the IBIS file and for fast simulation it
should pick the value from the min location.  But it doesn't
say that the model maker should put the big values into the
min location etc...

Arpad
=================================================================

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Hermann Ruckerbauer
Sent: Wednesday, May 26, 2010 6:59 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: IBIS min, typ and max. values

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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