FreeLists / si-list / [SI-LIST] Re: I-V vs V-T endpoints In IBIS

["Timothy Coyle" <Timothy.Coyle@xxxxxxx>]

Hi Stephen,
I guess I wasn't very clear on what I was asking. I was trying to get a 
better understanding of how different simulators use the V-T data, and 
when I have less than 5
or 2% mismatch, how much of an affect on my accuracy occurs.  I think your 
response and others answered this for me. 

Thanks to everyone who responded,

Tim





stephen.peters@xxxxxxxxx
06/03/2002 04:27 PM

 
        To:     Timothy Coyle/Americas/NSC@NSC, si-list@xxxxxxxxxxxxx@Internet
        cc: 
        Subject:        [SI-LIST] Re: I-V vs V-T endpoints In IBIS



Hi Tim:

  I would be very cautious about ignoring any warnings from the IBIS 
parser,
especially the DC endpoint warning.  This warning indicates that the I-V 
and
V-T tables do not correlate -- i.e. after the output transitions the final
(DC) value recorded in the V-T table does not match what the I-V table 
says
it should be (given the load resistor).  It's a red flag that something
isn't correct with the model. End point mismatches could be due to a 
number
of reasons:

1. The model creator did not properly document the R_fixture or V_fixture
(load resistance or voltage) used when creating the [Rising Waveform] or
[Falling Waveform] tables.

2. The model creator did not let the output make a full transition (i.e. 
the
V-T data was truncated before the output reached it's final DC level)

3. The I-V and V-T data were taken at different 
process/voltage/temperature
corners.

At any rate, don't ignore it.

(Also, I would caution against using the [Ramp] data rather than the V-T
tables.  IF the model creator included V-T tables there is a strong
likelihood that the model was not validated using the [Ramp] data.)

  Regards,
  Stephen Peters
  Intel Corp.

 

-----Original Message-----
From: Timothy Coyle [mailto:Timothy.Coyle@xxxxxxx]
Sent: Monday, June 03, 2002 9:57 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] I-V vs V-T endpoints In IBIS


Hello,
I am looking for some clarification on how the I-V and V-T data is used 
from an IBIS file.  When I make an IBIS file and run it through the 
parser, 
let's say I get a DC endpoint mismatch warning. I know that a load line is 

applied to the I-V data and the enpoints of this are matched to the 
endpoints
of the V-T data.  I'm not sure of the importance of why these endpoints 
should match.  My understanding is that the I-V data is used to model the 
endpoints 
of the device, where the V-T data is used to model the low-to-high and 
high-to-low transitions. I know that in HSPICE, when there is a mismatch, 
the V-T 
endpoint is modified to match the I-V endpoint. So how does this warning 
affect the accuracy of the model? I'm thinking the V-T data plays a bigger 

role than I think? 
I've correlated SPICE to IBIS models with good results even with these 
mismatches.  And you can use the Ramp data and get the same result without 

even using
the V-T data.  I have a customer who is asking about this, and I want to 
tell them that it's okay to have the warnings because of the above 
reasons, but I'm 
not entirely sure about that. 

Thanks for any responses,
Tim


------------------------------------------------------------------
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:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at: 
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages 
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:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at: 
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages 
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:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu