Lynne The problem is not the load resistance but the voltage it is terminated to, Vref = 0 in this case. Lowering the Rref is not going to help, Rref should be whatever resistance the datasheet says it should be. There will be no current flowing in this driver if both the load and the driver are tied to ground. From I=E/R, I will be 0 if E=0. I've seen this mistake way too many times and likely made it myself once or twice. I'm not sure what you mean by (Rref of 50 ohms for the transmission line load, in parallel with the pullup load.) Could you expand on it? What do you mean in parallel with the pullup load? 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 From: owner-ibis-users@server.eda.org [mailto:owner-ibis-users@server.eda.org] On Behalf Of Lynne D. Green Sent: Thursday, October 25, 2007 10:02 AM To: 'Ibis Model'; 'Server EDA' Subject: RE: [IBIS-Users] re: Warning message for IO_open_drain model Hello, Timmy, The warning says if you hook the circuit up (in simulation), it will only switch a few millivolts, not enough for the output to cross Vmeas. You might try setting Rref and Vref to the normal load for this buffer. (Rref of 50 ohms for the transmission line load, in parallel with the pullup load.) One could also look at the V-t curves, to see where their endpoint voltages are. If you would like your model reviewed, the IBIS Model Review Committee welcomes models that pass the IBIS parser. Best regards, Lynne "IBIS training when you need it, where you need it." Dr. Lynne Green Green Streak Programs http://www.greenstreakprograms.com 425-788-0412 lgreen22@mindspring.com _____ From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Ibis Model Sent: Wednesday, October 24, 2007 11:04 PM To: Server EDA Subject: [IBIS-Users] re: Warning message for IO_open_drain model Hi everyone, I get a warning message "TYP VI curves cannot drive through Vmeas given load Rref=1e+006 Ohms to Vref=0V" for IO_open_drain model. What does this message mean ? Regards, Timmy __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com -- This message has been scanned for viruses and dangerous content by <http://www.mailscanner.info/> MailScanner, and is believed to be clean. -- This message has been scanned for viruses and dangerous content by <http://www.mailscanner.info/> 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 Thu Oct 25 10:45:42 2007
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