The IBIS specification does not associate the numbers with any meaning, i.e. a small number doesn't necessarily mean slow/fast or best/worst. This is because from a signal integrity or timing point if view you can some times argue it both ways. For example, a small C_comp could result in a faster edge rate, but at the same time it can also cause more overshoot and ringing. If the timing is such that the ringing has to settle before you have a valid signal, you got worse timing from a smaller C_comp. So in this case, is the smaller C_comp a best case or a worst case scenario? For this reason, the IBIS specification says that you put the small numbers in the min place, and the big numbers in the max case. There is only one exception, as Radovan mentioned it, which is the temperature. Depending on whether you have a bi-polar or CMOS device, you will either put the high temperature (the weak condition) in the max or min place, respectively. This was done so that a tool can apply different algorithms to the model if they so desire, knowing what type the device is. Arpad ============================================================= -----Original Message----- From: owner-ibis-users@server.eda.org [mailto:owner-ibis-users@server.eda.org] On Behalf Of Vuletic Radovan (QAG PX D PDE) Sent: Monday, March 23, 2009 8:15 AM To: Lars Snith; ibis-users@server.eda.org Subject: RE: [IBIS-Users] Correct use of [Temperature Range] Hi Lars, usually in IBIS modeling I refer to the typ, min and max PVT cases as to the nominal, slow and fast PVT cases. In max (fast) PVT cases usually one should have the best transistor device parameters ("fastest" transistors), highest voltage and - now comes the trick (if there is one at all) - lowest temperature for CMOS circuits (since CMOS transistors usually have negative temperature coefficient - meaning lower temperature yields in higher current --> faster switching) or highest temperature for bipolar transistors (devices) since usually they have positive temperature coefficient and therefore at higher temperatures they deliver higher current (in some cases some smoke as well :-)) Similar (but opposite) in slow PVT case: put there slowest device models, lowest voltage and highest temperature for CMOS or lowest temperature for bipolar devices. Of course, I can imagine that in some very special cases some deviations from above rules could happened. So, if you are having IBIS models of some vendor that uses both CMOS and bipolar technologies having different temperatures for the same PVT case I would say that it makes sense - if that is not the case, I would than directly clarify with the model provider if there is a bug in the model or not. I hope this helps. Best regards / Mit freundlichen Gru?en / S postovanjem Radovan Vuletic Staff Engineer Product Development Qimonda AG QAG PX D PDE MUC/10.2.236 AP 3 Am Campeon 1-12 D-85579 Neuebiberg Germany Phone: +49 (0)89 60088 1233 Fax (PC): +49 (0)89 60088 45 5305 Mobile: +49 (0)160 7476262 E-mail: radovan.vuletic@qimonda.com Web: http://www.qimonda.com/ ======================================================================== ====== Qimonda AG Chairman of the Supervisory Board/ Aufsichtsratsvorsitzender: Peter J. Fischl Management Board/ Vorstand: Kin Wah Loh (Chairman/ Vorsitzender), Thomas J. Seifert Register Court/ Registergericht: Munchen HRB 152545, Seat/ Sitz: Munchen ======================================================================== ====== -----Original Message----- From: owner-ibis-users@server.eda.org [mailto:owner-ibis-users@server.eda.org] On Behalf Of Lars Snith Sent: Monday, March 23, 2009 1:27 PM To: ibis-users@server.eda.org Subject: [IBIS-Users] Correct use of [Temperature Range] Hello Friends, Let me once and for all try to nail down an issue that seem to be a constant source of confusion. The IBIS model syntax defines the triplet order [typ] [min] [max]. But this relates to the overall case, not the individual parameter, right? So to make things match the real operational case the [min] of [Temperature Range] would really need to be the maximum temperature, right? Looking at what others do is not much help here, I see examples of both variants, frequently from the same vendor(!). So an authorative answer would be appreciated. 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