[SI-LIST] Re: ESD Structure in IBIS
- From: Umesh Painaik <upainaik@xxxxxxxxxxxx>
- To: Timothy.Coyle@xxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Fri, 9 Aug 2002 16:11:03 -0400
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
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