From: David Huhn
Subject: LT SwitcherCAD Current Source Help
Date: Thu, 12 Sep 2002 11:30:13 -0400
Organization: Merit Network
NNTP-Posting-Date: Thu, 12 Sep 2002 15:30:01 +0000 (UTC)
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I am not modeling the FET itself, but the IC driver chip.
Perhaps I should have been more clear in my inital posting, however, one
parameter in my model is the propagation delay from my IC input to the
change in IC output voltage.
I was hoping to find some method of incorporating that known delay into
my circuit model.
Thank you for the suggestions, I will continue working on it.
David M. Huhn
Kevin Aylward wrote:
> "David Huhn" wrote in message
>>I am a student working on a software model(in LT SwitcherCAD III) for
>>motor driver and am trying to model the current chopping action of the
>>FET driver IC that is going to be used.
>>I am trying to do this with a voltage dependent current source. I
>>read through the help and tried unsucessfully to come up with even a
>>Ideally, my current source would provide X amps if the voltage at the
>>V_sense node is less than 3.4, and 0 amps if the voltage at the sense
>>node is greater than 3.4.
>>I apologize for the trivial nature of this question, but I would
>>appreciate any suggestions on how to complete this model.
>>Thank you for your time.
> If you are modelling a fet you can do the obvious and use a fet!, or you
> can use a voltage controlled switch, i.e.
> .MODEL VSwitch SW(RON=0.1 ROFF=100Meg VT=3.4 VH=1m)
> You can use this switch to switch the voltage to the VCCS if you put a
> resistor across the VCCC inputs.
> Kevin Aylward
> SuperSpice, a very affordable Mixed-Mode
> Windows Simulator with Schematic Capture,
> Waveform Display, FFT's and Filter Design.