RE: [IBIS-Users] hspice vs IBIS model correlation at different capacitive loads

From: Ummalaneni, Venu Babu \(Venu\) <venubabu_at_.....>
Date: Tue Dec 20 2005 - 04:02:49 PST
Itzik Peleg and all,
 
Thank you very much for your help. Please see my answers in line with
your comments.
 
1. This buffer operation is intended for a load resistance of more than
5k ohm. 
2. Yes, you are right. I should allow more transient simulation time for
min corner.
However, reported behavior (correlation of hspice vs IBIS) is for typ
corner.
 
Even I have tried with 50, 100, 500 & 5k ohm terminations for capturing
V-t waveforms. But I could not see any improvement in the correlation. I
am still investigating this issue.
 
 
                 Thanks & Best Regards,
Venu

 

 

-----Original Message-----
From: Itzik Peleg [mailto:itzikpe@marvell.com] 
Sent: Thursday, December 15, 2005 7:09 PM
To: Ummalaneni, Venu Babu (Venu); ibis-users@eda.org; ibis@eda.org
Subject: RE: [IBIS] RE: [IBIS-Users] hspice vs IBIS model correlation at
different capacitive loads

 

Hello Venu

 

Here are my comments reviewing your model:

 

1.       The loading condition is 1k ohm !? isn't this buffer should be
used in 50 ohm environment? If the answer is yes then you should use 50
ohm. 

2.       It seems like the slow didn't finish the complete transition.
You should allow more time for the V(t) simulation in order that the
response get to steady state (like the maximum case in red). This also
causing the warning that you have when using IBIS check:

**************************************************************

      WARNING - Model ATA4N1K000: The [Rising Waveform] 

      with [R_fixture]=1000 Ohms and [V_fixture_min]=0V

      has MIN column DC endpoints of  0.00V and  2.78v, but

      an equivalent load applied to the model's I-V tables yields

      different voltages (-0.00V and  2.92V),

      a difference of  0.00% and  4.69%, respectively.

WARNING - Model ATA4N1K000: The [Falling Waveform] 

      with [R_fixture]=1000 Ohms and [V_fixture_min]=3V

      has MIN column DC endpoints of  0.21V and  3.00v, but

      an equivalent load applied to the model's I-V tables yields

      different voltages ( 0.05V and  3.00V),

      a difference of  5.54% and  0.00%, respectively.

      ****************************************************************

3.       Based on the 2 previous points I can think of a buffer for slow
interface that should be used in 50 ohm environment. If this is the case
you should allow the transient simulation more time on 50 ohm.   



 

Hope this will halp.

 

 

--
Regards
 
Itzik Peleg
Board Technology Group
 
Marvell Semiconductor Israel Ltd
6 Hamada Street 






Mordot HaCarmel Industrial Park






Yokneam 20692, ISRAEL
 
Email - itzikpe@marvell.com
Tel   - +972 4  9091192
Cell  - +972 54 4452482
Fax   - +972 4  9091501
WWW Page: http://www.marvell.com <BLOCKED::http://www.marvell.com> 
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Thank you!
========================================================================
  _____  


From: Ummalaneni, Venu Babu (Venu) [mailto:venubabu@agere.com] 
Sent: Thursday, December 15, 2005 1:07 PM
To: Itzik Peleg; Todd Westerhoff (twesterh); ibis-users@eda.org;
ibis@eda.org
Subject: RE: [IBIS] RE: [IBIS-Users] hspice vs IBIS model correlation at
different capacitive loads

 

Itzik Peleg,
 
Thanks for your concern. I think there is no such feedback.
 
Here, I am attaching the IBIS model.
 
Thanks & Regards,
Venu

 

 

-----Original Message-----
From: Itzik Peleg [mailto:itzikpe@marvell.com] 
Sent: Wednesday, December 14, 2005 12:50 PM
To: Ummalaneni, Venu Babu (Venu); Todd Westerhoff (twesterh);
ibis-users@eda.org; ibis@eda.org
Subject: RE: [IBIS] RE: [IBIS-Users] hspice vs IBIS model correlation at
different capacitive loads

 

Hello Venu

 

Just to add one more possibility doe's your buffer has a feedback?

Could you attached the IBIS model, or show the I(V) and V(t) curves?

 

--
Regards
 
Itzik Peleg
Board Technology Group
 
Marvell Semiconductor Israel Ltd
6 Hamada Street 













 














 
Mordot HaCarmel Industrial Park











 














 
Yokneam 20692, ISRAEL
 
Email - itzikpe@marvell.com
Tel   - +972 4  9091192
Cell  - +972 54 4452482
Fax   - +972 4  9091501
WWW Page: http://www.marvell.com <BLOCKED::http://www.marvell.com> 
========================================================================
This message may contain confidential, proprietary or legally privileged
information. The information is intended only for the use of the
individual or entity named above. If the reader of this message is not
the intended recipient, you are hereby notified that any dissemination,
distribution or copying of this communication is strictly prohibited.
If you have received this communication in error, please notify us
immediately by telephone, or by e-mail and delete the message from
your computer.
 
Thank you!
========================================================================
  _____  


From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of
Ummalaneni, Venu Babu (Venu)
Sent: Tuesday, December 13, 2005 2:49 PM
To: Todd Westerhoff (twesterh); ibis-users@eda.org; ibis@eda.org
Subject: [IBIS] RE: [IBIS-Users] hspice vs IBIS model correlation at
different capacitive loads

 

Todd,

 

Thanks for your inputs. 

 

I have verified the programming options of driver and it's fine. Here, I
am attaching the correlation waveforms of the simulations by using a 0.1
ohm resistor instead of transmission line in both load (5pF & 30pF)
cases. Still, I am seeing a bad correlation in 30pF case.

 

Please ignore my previously attached *.PDF.

 

Once again thanks for your response.

 

Best Reagrds,

Venu

 

 

-----Original Message-----
From: Todd Westerhoff (twesterh) [mailto:twesterh@cisco.com] 
Sent: Tuesday, December 13, 2005 5:43 PM
To: Ummalaneni, Venu Babu (Venu); ibis-users@eda.org; ibis@eda.org
Subject: RE: [IBIS-Users] hspice vs IBIS model correlation at different
capacitive loads

 

Venu,

 

How long is the transmission line you're using ... about 1ns?

 

Your IBIS driver in the 30pf case seems to be taking several round-trips
to charge the load where the HSpice driver doesn't - if this is a
programmable driver, is it possible the driver settings for the two
plots are different?  In the top plot for the 30pf case, the IBIS driver
looks like a much weaker output with a faster slew rate to me ...

 

Todd.


Todd Westerhoff
High Speed Design Group Manager
Cisco Systems
1414 Massachusetts Ave
Boxboro, MA 01719
email:twesterh@cisco.com
ph: 978-936-2149
____________________________________________
"Always do right.
 This will gratify some people and astonish the rest."

 

- Mark Twain

 

 

  _____  

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On
Behalf Of Ummalaneni, Venu Babu (Venu)
Sent: Tuesday, December 13, 2005 5:38 AM
To: ibis-users@eda.org; ibis@eda.org
Subject: [IBIS-Users] hspice vs IBIS model correlation at different
capacitive loads

Hi Gurus,

I have an ATA* IBIS model and it is correlating well with hspice model
when I am using a 5pF load followed by a transmission line. If I replace
the 5pF load with 30pF correlation is bad (particularly in 2nd page
waveform of attached PDF). 

Could some one comment on this, where it is going wrong?

Your comments/inputs are highly appreciated.

Attachments: ata4nik_5pf.pdf - hspice and IBIS model waveforms captured
using 5pF load

                    ata4nik_30pf.pdf - hspice and IBIS model waveforms
captured using 30pF load

Thanks & Best Regards,

Venu

<<ata4n1k_30pf.pdf>> <<ata4n1k_5pf.pdf>> 



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Received on Tue Dec 20 04:03:55 2005

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