[SI-LIST] Re: ESD Structure in IBIS
- From: "Abhijit Mahajan" <amahajan@xxxxxxxxxxxx>
- To: Timothy.Coyle@xxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Fri, 09 Aug 2002 10:23:52 -0700
Tim,
This is a common problem because the people who create the models do not
really care about the "beyond the rails" operation as much as operation
in normal operating regions.
They only way to fix this problem is for you to work with your
semiconductor device modeling group and ask them to generate accurate
models for you.
Another option is to get real data from lab measurement and extrapolate
it using linear approximation. Adding a small resistance to the spice
model may fix the problem but then the model is no longer accurate,
unless you can selectively add the resistor for only beyond rails
operation and merge the data with between rails operation. The
reistance
to be added will have to come from some empirical data, I suppose.
Regards,
Abhijit.
Timothy Coyle wrote:
>
> 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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