Fabio An open drain or open sink driver has only a pulldown output FET. Assuming it is operated between ground and a positive supply voltage it can only sink current from the load, not supply current to an external load. Thus the load needs to be terminated to a positive supply voltage. Most of the time this is the Vdd for the device but sometimes the pullup resistor can be terminated to Vdd/2 or some other voltage higher or lower than Vdd. A very common mistake in setting up this kind of driver in an IBIS model is to use a Vref of 0.00V. This will give an IBIS parser warning about the driver not being able to drive through Vmeas. Vref should be the termination voltage the load is connected to as used in the extraction of the VT waveforms. If the driver has an internal pullup resistor like you find in most CML drivers you still need to use an external load terminated to the appropriate voltage for the VT extractions. When extracting the IV characteristics you always remove any external load. In the case of an internal pullup resistor that characteristic should belong in the power clamp table, not in the pullup table. Regards, 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@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Fabio BRINA Sent: Wednesday, December 05, 2007 9:07 AM To: ibis@server.eda-stds.org; ibis-users@server.eda.org Subject: [IBIS] Open drain load conditions Hi ibis experts, I need some explanation about "Open drain" model type: In this case, which are the load conditions recommended for V-T waveform? Have I to introduce R_fixture between Pin and Power to extract V-T? have I to remove it when I consider Pull up waveform? Thank you, Best Regards, Fabio Brina -- 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 1993 -- 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 Wed Dec 5 09:40:01 2007
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