Hi Tim I assume you are getting the ground clamp from spice. I have always faced the ideal diode problem with spice reverse bias junction diodes and ESD diodes. The solution is the parameter ijth (version 2001.2 on). This parameter is by default set to 1 for diodes and nmos or pmos. If you set it to smaller e.g. 0.001, it limits the current through these diodes and eliminates the 200A current. You will see more realistic currents this way. Again these are much beyond the operating range, hence they should not affect your simulation. Hope this helps. Umesh Painaik Mentor Graphics formerly Innoveda -----Original Message----- From: Timothy Coyle [mailto:Timothy.Coyle@xxxxxxx] Sent: Friday, August 09, 2002 7:20 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] ESD Structure in IBIS Hi, I am trying to obtain a ground clamp curve of an input through simulation for IBIS. The issue I'm having is at -Vcc my current is -200A, which might not be correct. I have some characterization data of the actual part, which includes some Clamp Current Data. So forcing a current of 18mA I get a voltage of .53V. When I look at my simulated ground clamp curve, at - .5V I roughly have -18mA of current. It seems the ground clamp curve is accurate for the operating region of the device (-.5V to 2.5V), but beyond that I'm not understanding what's going on. (Not sure either if it is accurate to use this one data point for correlation) The ESD structure is a grounded gate MOSFET architecture, which I am not that familiar with. My simulation setup is sweeping the input, leaving the output floating, and applying voltage to power pin. For input clamp diode ESD structures, in the past I've added a small resistor to compensate for the ideal diode. Do I need to do the same compensation for the grounded gate MOSFET structure? How are other people correlating their ground clamp curves for the required full IBIS sweep? Can I get this data from a curve tracer without blowing up the part? Regards, Tim ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu