Re: [IBIS-Users] Correct use of [Temperature Range]

Hello Arpad,

Thank You for additional clarification. But I would argue that there is 
one more case, chip-level RLC values. The max values should go into the 
"min" column, right?

Best regards,  Lars


Muranyi, Arpad wrote:
> 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/
> 
> 
> ========================================================================
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> Qimonda AG
> Chairman of the Supervisory Board/ Aufsichtsratsvorsitzender: Peter J.
> Fischl
> Management Board/ Vorstand: Kin Wah Loh (Chairman/ Vorsitzender), Thomas
> J. Seifert
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> 
> 
> 
> -----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.



-- 
Those who can, Do
Those who can't, Simulate

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