I'm getting started with LTspice and I am trying to import a FAN7392 spice model into LTspice.

Normally the file would be either .MODEL or . SUBCKT and you could import it using these instructions, but my file doesn't have either of those commands and instead it just has a * Begin: statement and an End Statement.

I can't seem to find a guide on how to import an encrypted LTspice file. Does anyone know how to import my FAN7392 into LTspice?

  • \$\begingroup\$ I start to wonder. Why would someone make an encrypted LTspice file though? \$\endgroup\$ Aug 31, 2022 at 8:02
  • \$\begingroup\$ @ChristianidisVasileios It's for IP protection. Or your average secrecy. \$\endgroup\$ Aug 31, 2022 at 8:11
  • 1
    \$\begingroup\$ One interesting thing is if you run an .op simulation and then look at the LTspice error log (CTRL+L), it'll show you the small signal parameters for all semiconductors in the simulation including ALL subcircuits. So you can basically see what kind of semiconductor devices exist within the encrypted model. It doesn't tell you much, but for the FAN7392 it only shows 10 diodes and 4 BSIM3 MOSFETS....which tells me that it's not a full IC model but a simpler (and likely faster) behavioral model. \$\endgroup\$
    – Ste Kulov
    Sep 1, 2022 at 4:12

1 Answer 1


In the zip file you downloaded there are two files:
FAN7392.asy (the schematic symbol)
FAN7392_REV1p2_ltspice.txt (the model file)

  • Create a new project and save this project to a directory.
  • Unpack the zip archive to the project directory.
  • Add the schematic symbol in to your schematic. In the Select Component Symbol dialog window, select the project directory in the Top Directory selection box at the top of the dialog window. This will show the listing of the schematic symbols in your project directory.
  • Finish the schematic.
  • Be sure to add the following directive (use s to enter a directive):
    .inc FAN7392_REV1p2_ltspice.txt

An example is shown below.

enter image description here

  • 2
    \$\begingroup\$ Manually adding the .lib or .inc SPICE directive is a perfectly good way to do it, but I think it's better (in my opinion) to instead open the symbol file (.asy) in LTspice, then go to Edit->Attributes->Edit Attributes, and put the FAN7392_REV1p2_ltspice.txt as the "ModelFile" attribute. Then the symbol auto-includes the file every time it's used. Honestly, onsemi should've shipped the symbol file like this in the first place. Boo to them. \$\endgroup\$
    – Ste Kulov
    Aug 31, 2022 at 1:53
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    \$\begingroup\$ @SteKulov Hallelujah to adding the ModelFile attribute to the .asy file - which is normally how I do it. However, the include directive gets the OP going without modifying the source and possibly confusing the issue. \$\endgroup\$
    – qrk
    Aug 31, 2022 at 3:41

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