Lance, Sorry, but I must disagree with you... There are at least two reasons the IBIS specification says that the small value of C_comp should be in the min place and the big value in the max place. One is that C-Comp doesn't always track with other effects. For example, you can get a weak I-V curve by reducing the supply voltage, but that will not change the value of the die capacitance. And there are other process related effects which may not track either. The other is that it is very easy to get mixed up in the terminology. People often associate worst case with slow, and best case with fast. But think of an example where the buffer switches very fast, has very small capacitance. In this case the transition will most likely have some ringing, especially in reflective environments. If the ringing after the edge is large enough, it may enter the "forbidden zone" where the receiver may switch. For this reason the timing of the system will have to wait for the ringing to settle, and from an SI perspective the fast buffer may actually become the worst case. Increasing the die capacitance may help in slowing down the buffer and/or reducing the ringing. This could result in much better SI timings, even though the buffer is "slower". These were the primary reasons for writing the IBIS specification the way it is. It is really the simulator tool's and its user's responsibility to pick the correct combinations of the min and max values from the IBIS model. To cover all possible scenarios you may need to do more combinations to find out what could cause systems to fail. Arpad ==================================================================== -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Lance Wang Sent: Thursday, May 27, 2010 10:17 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: IBIS min, typ and max. values We might need to think differently for this. For simulators, how do they know which corner in IBIS is slow or fast or nominal? They just use Max, Min and Typ corners. Easy! Do they know if you put the corners in the wrong places? Definitely not. What IBIS spec suggested is to put slow in Max and fast in Min to have simulators pick the correct one for you since they might have default setting as min=fast and max=slow. Some simulation software even allow you changing the relationships as you needed. For an example, Cadence PCB SI. For the buffer-self, when you have 3 spice netlists for each corners, the C_comp value is set since it is an extracted value as the same as its IV/VT data. Your c_comp needs to be with the other extracted data in the same corner for sure to have correct simulation results. I have seen some buffers' min c_comp values larger than max c_comp values. And min is faster. In this case, I would suggest you just have them as is. IBIS golden parser might give you warning messages. But it should not give Errors. Hope this clears a bit. Best regards, Lance Wang 978-764-2298 IO Methodology Inc. www.iometh.com -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad Sent: Thursday, May 27, 2010 9:50 AM To: Sudhanshu SINGH; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: IBIS min, typ and max. values Follow the suggestion in the spec, put the big values in the max location and the small values in the min location... The simulator will pick and choose for you. For example, if you read the HSPICE manual, you will find a table in there which explains what values it will pick from the IBIS file for typ min max fast slow simulation settings in the B-element... Arpad ========================================================== -----Original Message----- From: Sudhanshu SINGH [mailto:sudhanshu.singh@xxxxxx] Sent: Thursday, May 27, 2010 8:10 AM To: si-list@xxxxxxxxxxxxx; Muranyi, Arpad Subject: RE: [SI-LIST] Re: IBIS min, typ and max. values Hello All, In my case I have seen that spice Vs IBIS correlation is better if the c_comp values are put in typ/min/max tables exactly as they are extracted. Even if the magnitude wise order is not strictly followed as in the IBIS spec. What is then the best approach to put c_comp values in IBIS tables? Thanks in advance, Best Regards, Sudhanshu -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad Sent: Thursday, May 27, 2010 5:00 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: IBIS min, typ and max. values 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 >>> >>> >>> ------------------------------------------------------------------ >>> To unsubscribe from si-list: >>> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field >>> >>> or to administer your membership from a web page, go to: >>> //www.freelists.org/webpage/si-list >>> >>> For help: >>> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field >>> >>> >>> List technical documents are available at: >>> http://www.si-list.net >>> >>> List archives are viewable at: >>> //www.freelists.org/archives/si-list >>> >>> Old (prior to June 6, 2001) list archives are viewable at: >>> http://www.qsl.net/wb6tpu >>> >>> >> >> >> No virus found in this incoming message. >> Checked by AVG - www.avg.com >> Version: 9.0.819 / Virus Database: 271.1.1/2895 - Release Date: 05/25/10 >> > 08:26:00 > >> >> > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > List technical documents are available at: > http://www.si-list.net > > List archives are viewable at: > //www.freelists.org/archives/si-list > > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > List technical documents are available at: > http://www.si-list.net > > List archives are viewable at: > //www.freelists.org/archives/si-list > > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > > > > > No virus found in this incoming message. > Checked by AVG - 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