Subject: RE: [IBIS-Users] FW: Modelling an open drain driver
From: Angulo, John (john_angulo@mentorg.com)
Date: Mon Nov 25 2002 - 14:40:26 PST
In the case of most open-drain or open-source models, a single pair of V-T tables, one rising and one falling, is generally adequate to define the turn-on and turn-off behavior of the buffer. Since the intended net load on your buffer is about 60 ohms at the start of switching (Rpullup > 1.5 kohm), R_fixture = 60 ohms sounds fine. The point is to characterize the transient behavior of the device. A V_fixture of either 2.5 or 3.3 V will probably be adequate. No harm in keeping all four tables you currently have, however. No tool should be confused by them, and the additional information may result in slightly better accuracy. I would recommend double checking that the model passes the official parser and submitting it to the Model Review Committee for feedback from tool vendors.
Best regards,
John Angulo
Hyperlynx Products
Mentor Graphics Corp.
john_angulo@mentor.com
425-869-2320
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