Link IC-CAP to the LTspice Simulator

Blog Post created by rajsodhi Employee on Oct 2, 2017



LTspice is a freeware SPICE simulator offered by Linear Technologies (now a division of Analog Devices Inc.). LTspice was originally called “SwitcherCAD” and was designed with switch-mode power supplies in mind. As a result, it is widely used in power electronics. IC-CAP may be used to generate device models based on measured data using multiple simulators: not only our own ADS Transient and Harmonic Balance (for periodic state state) simulators, but also transient analysis in LTspice, giving engineers the option to create workflows as needed.  For an engineer that might want to generate a model based on measured data using LTspice as the simulation engine, here's a look at how you do that.

Flow diagram, showing LTspice to IC-CAP link


But before delving into the details of that process, it's worth noting that as of this writing, the LTspice documentation describes support for seven different MOSFET device models:


2MOS2 (A. Vladimirescu and S. Liu, October 1980)
3MOS3, a semi-empirical model
4BSIM (B. J. Sheu, D. L. Scharfetter, and P. K. Ko, May 1985)
5BSIM2 (Min-Chie Jeng, October 1990)
6MOS6 (T. Sakurai and A. R. Newton, March 1990)
8BSIM3v3.3.0 from University of California, Berkeley, July 29, 2005
9BSIMSOI3.2 (Silicon on insulator) from the BSIM Research Group, February 2004.
12EKV 2.6 (M. Bucher, C. Lallement, F. Theodoloz, C. Enz, F. Krummenacher, June 1997.)
14BSIM4.6.1 from the BSIM Research Group, May 18, 2007.
73HiSIMHV version 1.2 from the Hiroshima University and STARC.

How to Link IC-CAP to LTspice

If you have no background on how to link IC-CAP to an external simulator, I recommend you read my previous post
entitled, “Link the IC-CAP Modeling Tool to External Simulators.” It will provide you with an overview of the basic process, along with some troubleshooting tips.


LTspice is not officially supported by IC-CAP. However, we have a workaround to successfully link IC-CAP to LTspice IV by disguising it as a SPICE3 look-alike. To date, this workaround has not yet been tried on LTspice XVII.


Assuming you have LTspice installed on your system, here are the steps:

  1. Append the following line into your $ICCAP_ROOT/iccap/lib/usersimulators file.

    ltspice spice3 $ICCAP_ROOT\src\ltspice3.bat "" CANNOT_PIPE

    We used spice3 as the template_name, so that IC-CAP will treat the simulation input/output files as if it were for SPICE3, which is natively supported.

  2. Download the ltspice3.bat file from the attachment below.

    Note, the file was renamed to ltspice3.txt for security concerns. After you download it, please rename it back to ltspice3.bat.

    Open and edit ltspice3.bat on line 30. Make sure it reflects the correct path to the LTSpice IV executable scad3.exe, as shown below:

  3. Move the ltspice3.bat file to directory $ICCAP_ROOT/src.

  4. Restart IC-CAP.

Verify the Simulation Link to LTspice IV


Now, let’s verify that it works, to ensure we can indeed use LTspice as the simulator engine for IC-CAP model parameter extraction. To do that:

  1. Load the following *.mdl example file from within the IC-CAP program:../Examples/model_files/mosfet/nmos3.mdl
  2. In the model Variables, add the variable SIMULATOR and set it to ltspice.


  3. Go to the /large/idvg/ setup, and clear out the simulated data using Clear -> Simulated. Any previously saved simulation will be gone.


    We now see only the measured data (symbols) on the plot, whereas simulation data would be shown as solid:
  4. Simulate.


  5. In the same DUT/Setup, open the plot tab under the /large/idvg/idvsvg plot, and confirm that the simulated data appears.


The simulated data is represented by solid lines on the plot.


So there you have it! By following this process, you can now use LTspice as your simulator for model parameter extraction within IC-CAP.