RE: [IBIS] Overshoot/Undershoot specs.

From: Anders Ekholm <anders.ekholm_at_.....>
Date: Tue Mar 04 2008 - 03:59:49 PST
Hi Eckhard.
That seems like a reasonable practical approach I can agree with, if I have both values and I make the model.
But from an IBIS perspective it is not clear from the spec how to interpret this info in a model.
 
When I get a model from a manufacturer with this data already there, how do I know which it is?
The IBIS standard does not seem to be specific here.
 
So if the manufacturer did put in the destructive undershoot like -1.0V and we simulate the
design and fulfill this figure, we are not sure it will function correctly?
 
By the way in your example I think you turned the values around.
 
destruction below  -0.3V  and malfunction  below  -0.4V
 
I suppose you meant:
 
destruction below  -0.4V  and malfunction  below  -0.3V
 
 
Best /Anders
 
 


________________________________

From: Lenski, Eckhard (NSN - DE/Muenich) [mailto:eckhard.lenski@nsn.com] 
Sent: den 4 mars 2008 12:44
To: Anders Ekholm; ibis@eda.org
Subject: AW: [IBIS] Overshoot/Undershoot specs.


Hello Anders,
 
1) General
 
if I interpret your question correct, you are looking for another overshoot parameter
 
e.g..
classic:
s-overshoot-low  :    -0.3V
d-overshoot-low  :    -1.0V
d-time:                    2ns
 
 
new : 
 
s-overshoot-low-destroy  :    -0.3V
s-overshoot-low-funtion   :    -0.2V
d-overshoot-low (-destroy)  :    -1.0V
d-time:                    2ns
 
 
it might be even possible, that this could be applied to the dynamic values as well.
 
 
2)  Treatment at NSN: 
 
I assume, that  at the moment, we are taking the warnings/errors from overshoot in this way
 
 
both cases will be bad for the design, either the device will be destroyed, or it will malfunction.
 
So we are using the worst case for the overshoot parameter, ( if both of these informations  exist )
 
 
e.g. 
 
destruction below  -0.3V  and malfunction  below  -0.4V
 
we are using the more restrictive for s-overshoot-low
so s-overshoot-low would be -0.3V
 
 
3)  What to do :
 
so either  the spec should describe this more exactly,
 
or if the community finds it necessary, we should write a bird and ask for additional overshoot parameters
 
 
Mit freundlichen Grüßen / Best regards / Cordiali saluti / ystävällisin terveisin

Eckhard Lenski 

Nokia Siemens Networks GmbH & Co. KG


COO RA RD BTS HW GERAN BTS&NB&CP Dev SDE

CAE libraries and models
Balanstr. 59

81541 München
Germany 
phone : +49 89 636 79002
fax : +49 89 636 78895
email: eckhard.lenski@nsn.com



Nokia Siemens Networks GmbH & Co. KG

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Registergericht: München / Commercial registry: Munich, HRB 163416

 

________________________________

Von: owner-ibis@eda.org [mailto:owner-ibis@eda.org] Im Auftrag von ext Anders Ekholm
Gesendet: Dienstag, 4. März 2008 10:53
An: ibis@eda.org
Betreff: [IBIS] Overshoot/Undershoot specs.




This text is taken from the 4.2 IBIS spec. 

--------------------------- 
The static overshoot subparameters provide the DC voltage 
values for which the model is no longer guaranteed to function 
correctly.  Typically these are voltages that would cause the 
physical component to be destroyed. 
-------------------------- 

This is a bit confusing, since what we get from our component vendors are two diffrent levels, one that will garantuee function and 

one that will garantuee that the component is not destroyed. 

And sometimes we get similar data for dynamic overshoot/undershoot parameters. 

The question is how to interpret the spec. are the spec talking about function or are the spec disussing destruction? 
As a user my design will have to fulfill my function so to me it would make sense it it did specify function requirements,

but as the spec is not clear here I do not know what component vendors put in their models. 

Is there a need to separate this two diffrent parameters in the IBIS spec? 

Best /Anders 


--------------------------------------------------------------- 
Anders Ekholm 
Senior Specialist Signal Integrity 
CDU and DXU HW design 

Ericsson Product Development Unit BTS 
SE-164 80 Stockholm, Sweden 
Tel: +46 8 404 27 58 
Fax: +46 8 757 23 40 
email: anders.ekholm@ericsson.com 
--------------------------------------------------------------- 





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Received on Tue Mar 4 04:03:25 2008

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