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

hspice vs IBIS model correlation at different capacitive loadsAre both
simulations using the same package parasitics?

Tom Dagostino
Teraspeed(R) Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
tom@teraspeed.com
www.teraspeed.com

Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
401-284-1827

  -----Original Message-----
  From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org]On Behalf
Of Ummalaneni, Venu Babu (Venu)
  Sent: Tuesday, December 13, 2005 4:49 AM
  To: Todd Westerhoff (twesterh); ibis-users@eda.org; ibis@eda.org
  Subject: 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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