Sandeep, This is not too surprising, although the amount of mismatch is larger than what I have seen in other cases. The mismatch happens because the IBIS model cannot "extrapolate" to other load impedances if your model only has data obtained at one value of R_fixture. This is why the specification allows multiple sets of V-t curves at different R_fixture values, although this capability is not supported by many tools. Think about it this way. The model is supposed to reproduce waveforms. The data that is put into the model is generated under certain conditions. The IBIS model will only be able to reproduce the waveforms exactly if the conditions in your simulations are the same as when the data was generated. The rest is guesswork... Arpad ==================================================== -----Original Message----- From: owner-ibis-users@server.eda.org [mailto:owner-ibis-users@server.eda.org] On Behalf Of Sandeep S K Sent: Friday, September 26, 2008 8:04 AM To: ibis-users@server.eda.org Subject: [IBIS-Users] Open drain buffer : Discrepency in IBIS model vs SPICE model simulations Hi I am generating an IBIS model for an open drain buffer (I2C). The simulated waveforms match when I use a 50 ohm (which is what was used for V-t extraction) load connected to VCC, Whereas when a different load is used I see a mismatch in the waveforms. Attached are the ibis model and a snapshot of waveforms when 100 ohm load was used. Can you please suggest why. Thanks and Regards Sandeep -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org |with the appropriate command message(s) in the body: | | help | subscribe ibis <optional e-mail address, if different> | subscribe ibis-users <optional e-mail address, if different> | unsubscribe ibis <optional e-mail address, if different> | unsubscribe ibis-users <optional e-mail address, if different> | |or e-mail a request to ibis-request@eda-stds.org. | |IBIS reflector archives exist under: | | http://www.eda-stds.org/pub/ibis/email_archive/ Recent | http://www.eda-stds.org/pub/ibis/users_archive/ Recent | http://www.eda-stds.org/pub/ibis/email/ E-mail since 1993Received on Tue Sep 30 11:18:30 2008
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