LTspice® Devices

Some devices have been developed to allow compatibility with LTspice® models. In particular some Op-amp models for the former Linear Technology Corporation are only available in a form that uses special LTspice® devices. Some of these devices have been implemented in Verilog-A and are incorporated in the standard SIMetrix product. (A Verilog-A license is not required to run these models).

The following table lists the devices available:

Device Name Details
OTA Axxx IN1P IN1N IN2P IN2N NC RAIL IOUT GND OTA parameters
SCHMITT Axxx INP INN NC1 NC2 NC3 OUTN OUTP GND SCHMITT parameters
OR Axxx IN1 IN2 IN3 IN4 IN5 OUTN OUTP GND OR parameters
BUF Axxx IN1 IN2 IN3 IN4 IN5 OUTN OUTP GND BUF parameters
AND Axxx IN1 IN2 IN3 IN4 IN5 OUTN OUTP GND AND parameters
XOR Axxx IN1 IN2 IN3 IN4 IN5 OUTN OUTP GND XOR parameters
VARISTOR Axxx INP INN NC1 NC2 NC3 NC4 OUT GND SCHMITT parameters
IDEAL DIODE Diode model using any of the parameters RON, ROFF, VFWD, VREV, RREV
VDMOS .MODEL VDMOS parameters
Extended Capacitor Enabled if any of parameters RSER, RPAR, CPAR, LSER, RLSHUNT or NOISELESS are specified
Extended Inductor Enabled if any of parameters RSER, RPAR, CPAR or NOISELESS are specified
Extended VCCS Enabled if VTO or DIR provided
Level 2 Switch Enabled with LEVEL=2 model parameter

The devices above accessed using the 'A' prefix letter have the possibility of being confused with XSpice devices which also start with the letter 'A'. However, all of the special LTspice® devices have 8 connections whereas the largest number of scalar connections for any XSpice device is 7 (for the J-K flip-flop). There are XSpice devices that have vector connections and for these it is possible to have 8 nodes and so these could be confused with LTspice® devices. Vector connections are enclosed with the characters '[' and ']' so to avoid conflict, devices that include these characters in node names will not be interpreted as LTspice® devices. The ':' character is also excluded as this delimits instance parameters for XSpice devices.

In addition, the following devices have been extended to add new parameters.

Device Name Details
Arbitrary source New parameters CPAR, RPAR and NOJACOB (non functional)
Switch New parameters VSER, ILIMIT and NOISELESS
Resistor New parameter NOISELESS

LTspice® Notes

Some additional features and changes have been made to enable LTspice® models to run correctly. These are listed below

  • Interpret the micro symbol ???MATH???\mu???MATH??? as 1e-6. This has been implemented solely for compatibility with LTspice; we do not recommend using this in SIMetrix schematics or netlists.

    SIMetrix will recognise both ANSI and UTF-8 encodings of this symbol. Note that the ANSI encoding is not universal. On some systems, in particular systems setup for Japanese, Chinese or Korean languages, the ANSI micro symbol (B5h) will display as a different character with most text editors. SIMetrix (and LTspice®) will still interpret the character as ???MATH???\mu???MATH??? and scale the preceding value accordingly. Finally, note that the UTF-8 encoding for the micro character (C2h B5h) is different to the encoding for the greek letter ???MATH???\mu???MATH??? (CEh BCh) but the two characters are visually indistinguishable. SIMetrix will also recognise the UTF-8 encoding of greek ???MATH???\mu???MATH??? as 1e-6.
  • Allow unquoted .PARAM expressions. This requires the setting .options LTspiceCompatibility=1
  • dnlim and uplim functions implemented for arbitrary source expressions
  • Capacitors defined using charge expressions in form Cxxx n1 n2 Q=expression

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