Amit The problem you are having is you are treating an open sink driver as a normal totem pole driver. The normal open sink has a pulldown device only. And in your case you have a pullup resistor tied to Vdd. You are treating the pullup resistor as a pullup transistor. Pullup transistors switch between off in the low state and on in the high state. But a pullup resistor is always present in the circuit, it is always pulling up the load. The pullup resistor belongs in the powerclamp table. The driver type should be open sink or open drain, not output. Regards, Tom Dagostino Teraspeed(R) Labs 13610 SW Harness Lane Beaverton, OR 97008 503-430-1065 503-430-1285 FAX 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@server.eda.org [mailto:owner-ibis-users@server.eda.org] On Behalf Of Amit KUMAR Sent: Monday, June 23, 2008 4:22 AM To: ibis-users@server.eda.org; ibis@server.eda.org Subject: [IBIS-Users] Problem in IBIS development Hello Experts, I am developing IBIS model for a cell which is NMOS open drain type. I have configured it as an output ibis model as the pullup resitor and pullup voltage values are fixed. The problem is that the spice curve is not smooth and there seems to be sudden change in voltage around 1.4 Volts. The ibis simulator is not able to replicate this behaviour. The comparison between spice and ibis with load=30pf is attached with this mail with the name spicevsibis. I have tried a lot but this behaviour of spice is not reproduced by ibis. I am attaching the ibis file I have developed with this mail. Kindly tell me what can be done to improve the performance of this ibis file. Thanks and Regards Amit -- 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 Mon Jun 23 09:15:43 2008
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