The SPICE circuit simulation program originated in the early 1970’s. (I believe the first PUBLIC release was in 1972 or '73.) That makes it almost half a century old! I won’t go into all the ways computing has changed over those five decades, but it’s a tribute to the program’s original authors that it remains a viable piece of software today.
Numerous commercial versions of SPICE have been developed and released (and, in some cases, abandoned) over that time span. Most of these included some kind of “improvements”, “supplements”, “additions”, or “extensions” of the original SPICE program. SPICE models that exploit such alterations may, or may not, be compatible with SPICE versions published by other companies. Fortunately, a true SPICE model file, or netlist file, is (like KiCAD’s files) human-readable. After a little study of the original SPICE syntax, most of the SPICE model files intended for a particular version of SPICE can be converted to other versions. If you can open a SPICE model file with a standard text editor (such as "Notepad++) then it can probably be used directly, or readily converted, for any SPICE-based simulator. Sometimes no conversion is necessary. I believe, for example, that LTSpice can read and process model files that use the PSPICE extensions. From the LTSpice “Help” file:
LTspice can, however, run PSpice semiconductor and behavioral models and is generally a much higher performance simulator, so you might move your PSpice simulations to LTspice.
The exceptions are the encrypted files provided by some publishers. Encryption is used to protect some perceived commercial advantage of a particular SPICE version. This might be a feature or capability added to the original SPICE program, or it might be some discovery or insight into modeling a device.In any case, encrypted files can only be used by the SPICE version they were intended for. Linear Technology, for example, publishes encrypted models for simulating their switching regulators with LTSpice. These model files are not usable with other SPICE simulators. As the LTSpice “Help” file says,
The LTspice SMPS macromodels are implemented in a combination of new proprietary native LTspice devices and/or a proprietary hardware description language. While it is possible, in principle, to develop generic SPICE or PSpice macromodels, the resultant simulation speed would not be viable.
LTSpice is deliberately insensitive to the file extensions of SPICE model files. “*.sub”, " *.lib", " *.mod", " *.mdl", " *.sp3", etc, are all equally acceptable to LTSpice. Don’t assume that an LTSpice model is encrypted just because it has the " *.sub" file extension!
LTSpice can produce netlists that are supposedly compatible with several commercial circuit simulators. You must tell LTSpice whose netlist you want to export, and the last time I looked KiCAD was NOT one of the choices.
For questions concerning LTSpice (and some questions about circuit simulation in general) the Yahoo LTSpice user’s group at LTSpice User’s Group is an excellent resource.
Dale
