Transient Analysis Options
  • AUTOSTOP
    stops a transient analysis after successfully calculating all functions (15.4) specified with the dot command .meas. Autostop is not available with the meas (17.5.42) command used in control mode.
  • CHGTOL=x
    resets the charge tolerance of the program. The default value is 1.0e-14.
  • CONVSTEP=x
    relative step limit applied to code models.
  • CONVABSSTEP=x
    absolute step limit applied to code models.
  • GMINSTEPS=x
    [*] sets the number of Gmin steps to be attempted. If the value is set to zero, the standard gmin stepping algorithm is skipped. The standard behavior is that gmin stepping is tried before going to the source stepping algorithm.
  • INTERP
    interpolates output data onto fixed time steps on a TSTEP grid (15.3.9). Uses linear interpolation between previous and next time values. Simulation itself is not influenced by this option. This option can be used in all simulation modes (batch, control or interactive, 16.4). It may drastically reduce memory requirements in control mode, and file size in batch mode, but care is needed not to undersample the output data. See also the command linearize (17.5.38) that achieves a similar result by post-processing the data in control mode. The Ngspice/examples/xspice/delta-sigma/delta-sigma-1.cir example demonstrates how INTERP reduces memory requirements and speeds up plotting.
  • ITL3=x
    resets the lower transient analysis iteration limit. The default value is 4. (Note: not implemented in Spice3).
  • ITL4=x
    resets the transient analysis time-point iteration limit. The default is 10.
  • ITL5=x
    resets the transient analysis total iteration limit. The default is
    1. Set ITL5=0 to omit this test. (Note: not implemented in Spice3).
  • ITL6=x
    [*] synonym for SRCSTEPS.
  • MAXEVITER=x
    sets the maximum number of event iterations per analysis point.
  • MAXOPALTER=x
    specifies the maximum number of analog/event alternations that the simulator will use to solve a hybrid circuit.
  • MAXORD=x
    [*] specifies the maximum order for the numerical integration method used by SPICE. Possible values for the Gear method are from 2 (the default) to 6. Using the value 1 with the trapezoidal method specifies backward Euler integration.
  • METHOD=name
    sets the numerical integration method used by SPICE. Possible names are `Gear' or `trapezoidal' (or just `trap'). The default is trapezoidal.
  • NOOPALTER=TRUE|FALSE
    if set to false, alternations between analog/event are enabled.
  • RAMPTIME=x
    During source stepping, this option sets the rate of change of independent supplies. It also affects code model inductors and capacitors that have initial conditions specified.
  • SRCSTEPS=x
    [*] a non-zero value causes SPICE to use a source-stepping method to find the DC operating point. The value specifies the number of steps.
  • TRTOL=x
    resets the transient error tolerance. The default value is 7. This parameter is an estimate of the factor by which SPICE overestimates the actual truncation error. If XSPICE is configured and 'A' devices are included, the value is internally set to 1 for higher precision. This slows down transient analysis with a factor of two.
  • XMU=x
    sets the damping factor for trapezoidal integration. The default value is XMU=0.5. A value < 0.5 may be chosen. Even a small reduction, e.g. to 0.495, may already suppress trap ringing. The reduction has to be set carefully in order not to excessively damp circuits that are prone to ringing or oscillation, which might lead the user to believe that the circuit is stable.