Simulator Options |

Below is the list of the options and their effect on the simulation. There are two kinds of options: those with values, and those without values. Options without values are flags that are activated by simply listing the option name.

Name | Type | Description |

GMIN | Real | Sets the minimum conductance (maximum resistance) of any device in the circuit. It also sets the value of the conductance that is placed in parallel with each pn junction in the circuit. Raising this value may help with simulation convergence in many circuits, but might decrease accuracy. Default = 1.0e-12S. |

PIVREL | Real | Sets the relative ratio between the largest column entry in the matrix and an acceptable pivot value. The value must be between 0 and 1. Default = 1.0e-3. |

PIVTOL | Real | Sets the absolute minimum value for a matrix entry to be accepted as a pivot. Default = 1.0e-13. |

Name | Type | Description |

ABSTOL | Real | The absolute tolerance for currents. Defines the smallest interesting current anywhere in the circuit. It should be set higher for power electronic circuits. Setting abstol too loose results in degraded accuracy. Setting abstol too tight prevents the simulator from converging. Default = 1pA. |

VNTOL | Real | Sets the absolute voltage tolerance of the program. Defines the smallest interesting voltage anywhere in the circuit. It should be set higher for high voltage circuits. Setting vntol too loose results in degraded accuracy. Setting vntol too tight can prevent the simulator from converging. The default value is intended for circuits with voltages between 1V and 10V. Default = 1µV. |

RELTOL | Real | The relative error tolerance of the program. The value must be between 0 and 1. Values closer to zero imply greater accuracy. Larger values mean faster simulation time, but less accuracy. Default = 0.001 (0.1%). |

ITL1 | Integer | Maximum number of iterations for a DC operating point analysis. This may need to be raised as high as 500 for many circuits. Default = 100. |

ITL2 | Integer | Maximum number of iterations per step in a DC sweep. This may need to be raised as high as 200 for some circuits. Default = 50. |

ITL4 | Integer | Sets the Transient Analysis timepoint iteration limit. Raising this value to 100 or more may help to eliminate "timestep too small" errors improving both convergence and simulation speed. Default = 10. |

SRCSTEPS | Integer | Sets the number of steps in the source stepping algorithm for DC (operating point) convergence. Default = 10. |

GMINSTEPS | Integer | Sets the number of steps in the GMIN stepping algorithm. When set to 0, GMIN stepping is disabled, making source stepping the simulator's default DC (operating point) convergence algorithm. Default = 10. |

NOOPITER | Flag | Skip directly to GMIN stepping algorithm. Default=NO (don't skip). |

RAMPTIME | Real | Controls turn-on time of independent sources and capacitor and inductor initial conditions from zero to their final value during the time period specified. This parameter can be useful for aiding convergence for circuits that are initially unstable, by realistically modeling the turn-on time of power supplies. Default=0.0 seconds. |

RSHUNT | Real | Value in ohms of resistors added
between each circuit analog node and ground, helping to eliminate
problems such as "singular matrix" errors. In SPICE simulators,
problems can arise with certain circuit topologies. One of the
most common problems is the absence of a DC path to ground at
some node. This may happen, for example, when two capacitors are
connected in series with no other connection at the common node.
The result is an ill-conditioned or nearly singular matrix that
prevents the simulation from completing. When used, this option
inserts resistors to ground at all analog nodes in the circuit.
In general the value of RSHUNT should be set to some very high
resistance (10^{12} or greater) so that the operation of
the circuit is essentially unaffected, but the matrix problem
are corrected.
Default=0 (no shunt resistors). |

PROBELOADRES | Real | Value in ohms of resistors added
between each probe node and ground. In general, the value of
resistor should be set to a very high resistance (10^{12}).
Default=10^{12}. |

Name | Type | Description |

METHOD | String | Sets the numerical integration method. Possible names are GEAR or TRAP (trapezoidal). Default = TRAP. |

MAXORD | Integer | 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 Euler integration. Default = 2. |

TRTOL | Real | Used in the LTE timestep control algorithm. This is an estimate of the factor by which SPICE overestimates the actual truncation error. Default = 7. |

CHGTOL | Real | Provides a lower limit on capacitor charge or inductor flux; used in the LTE timestep control algorithm. Default=1.0e-14 coulombs. |

Name | Type | Description |

DEFW | Real | Sets the MOS channel width. Default = 100um. |

DEFL | Real | Sets the MOS channel length. Default = 100um. |

DEFAD | Real | Sets the MOS drain diffusion area. Default = 0m². |

DEFAS | Real | Sets the MOS source diffusion area. Default = 0m². |

BADMOS3 | Flag | Uses the older version of the MOS3 model with the "kappa" discontinuity. Defaull=NO (don't use the older version). |

OLDLIMIT | Flag | Use SPICE2 MOSfet limiting. Default = No. |

BYPASS | Integer | Enables the device bypass scheme for nonlinear model evaluation. Inactive device bypass is a technique which is used to speed up the simulation by reusing the terminal conditions of devices which have not changed significantly during the past evaluation period. Turning the device bypass off will slow down the simulation. Default=1 (on). |

TRYTOCOMPACT | Flag | Applicable to the LTRA model. When specified, the simulator tries to condense LTRA transmission line's past history of input voltages and currents. Default=NO (don't compact). |

Name | Type | Description |

MAXOPALTER | Integer | Sets the maximum number of analog/event alternations for DC (operating point) convergence. Default=0. |

MAXEVTITER | Integer | Sets the maximum number of event iterations for DC (operating point) convergence. Default=0. |

NOOPALTER | Flag | Causes analog/event alternations during a DC operating point to be disabled. Default=No. |

CONVLIMIT | Flag | Disables convergence algorithm used in some built-in component models. Default=No. |

CONVSTEP | Real | Sets the limit of the relative step size in solving for the DC operating point convergence for code model inputs. Default=0.25. |

CONVABSSTEP | Real | Sets the limit of the absolute step size in solving for the DC operating point convergence for code model inputs. Default=0.1. |

AUTOPARTIAL | Flag | Enables the automatic computation of partial derivatives for each code model. Typically, you will provide the partial derivative computation in the code model and leave this option off in order to increase the speed of computations. Default=No. |

Name | Type | Description |

LONE | Real | Sets the value for the logic 1 state which is used in the analog behavioral element (B) with logic expressions. When a logic expression is evaluated as true (logic 1), the output of the logic expression will be this value. Default = 3.5. |

LZERO | Real | Sets the value for the logic 0 state which is used in the analog behavioral element (B) with logic expressions. When a logic expression is evaluated as false (logic 0), the output of the logic expression will be this value. Default = 0.3. |

LTHRESH | Real | Sets the value for the logic threshold which is used in the analog behavioral element (B) with logic expressions. Below this voltage level, a voltage will be evaluated as a zero. Above this level, a voltage will be evaluated as a one. Default = 1.5. |

In order to view or print the digital waveforms, you must convert the digital signals into analog signals using the following variables.

Name | Type | Description |

DGTPLOTONE | Real | Output value for state ONE. Default = 1.0. |

DGTPLOTZERO | Real | Output value for state ZERO. Default = 0.0. |

DGTPLOTUNKNOWN | Real | Output value for state UNKNOWN. Default = 0.5. |

DGTPLOTSTRONG | Real | Output value for strength STRONG. Default = 0.1. |

DGTPLOTRES | Real | Output value for strength RESISTIVE. Default = 0.6. |

DGTPLOTHIZ | Real | Output value for strength HI_IMPEDANCE. Default = 1.1. |

DGTPLOTUNDEF | Real | Output value for strength UNDETERMINED. Default = -0.4. |

Name | Type | Description |

DGTPWR | Real | Default digital power source value (node $G_DPWR). Used with devices that do not have the power pin. Default = 5.0 Volt. |

DGTGND | Real | Default digital ground source value (node $G_DGND). Used with devices that do not have the power pin. Default = 0.0 Volt. |

DGTMNTYMXTP | Integer | Propagation delay parameters selection. (0=min, 1=typ, 2=max). Default = 1. |

DGTMNTYMXTT | Integer | Transition time parameters selection. (0=min, 1=typ, 2=max). Default = 1. |

DGTMNTYMXLD | Integer | Input loading parameters selection. (0=min, 1=typ, 2=max). Default = 1. |

DGTMNTYMXDR | Integer | Output drive parameters selection. (0=min, 1=typ, 2=max). Default = 1. |

DGTMNTYMXIS | Integer | Supply current parameters selection. (0=min, 1=typ, 2=max). Default = 1. |

DGTMNTYMXVT | Integer | Voltage threshold parameters selection. (0=min, 1=typ, 2=max). Default = 1. |

DGTMNTYMXUS | Integer | User parameters selection. (0=min, 1=typ, 2=max). Default = 1. |

DGTMINSCALETP | Real | Scale factor used to determine minimum propagation delay. Default = 0.5. |

DGTMAXSCALETP | Real | Scale factor used to determine maximum propagation delay. Default = 1.5. |

DGTMINSCALETT | Real | Scale factor used to determine minimum transition time. Default = 0.5. |

DGTMAXSCALETT | Real | Scale factor used to determine maximum transition time. Default = 1.5. |

DGTMINSCALELD | Real | Scale factor used to determine minimum input loading (maximum input resistance). Default = 1.5. |

DGTMAXSCALELD | Real | Scale factor used to determine maximum input loading (minimum input resistance). Default = 0.5. |

DGTMINSCALEDR | Real | Scale factor used to determine minimum output drive capacity (maximum output resistance). Default = 1.5. |

DGTMAXSCALEDR | Real | Scale factor used to determine maximum output drive capacity (minimum output resistance). Default = 0.5. |

DGTMINSCALEIS | Real | Scale factor used to determine minimum supply current (maximum internal resistance). Default = 1.5. |

DGTMAXSCALEIS | Real | Scale factor used to determine maximum supply current (minimum internal resistance). Default = 0.5. |

DGTMINSCALEVT | Real | Scale factor used to determine minimum voltage threshold. Default = 0.5. |

DGTMAXSCALEVT | Real | Scale factor used to determine maximum voltage threshold. Default = 1.5. |

DGTMINSCALEUS | Real | Scale factor used to determine minimum user value. Default = 0.5. |

DGTMAXSCALEUS | Real | Scale factor used to determine maximum user value. Default = 1.5. |

MAXSIMWARN | Integer | Maximum warnings for Setup,Hold,Width violations. Default = 10. |

DGTNOINPUTLOAD | Flag | Disable analog loads on digital inputs. Default = NO. |

DGTDEFAULTIOVTH | Real | Default I/O model threshold voltage factor respect to vcc. Default = 0.2. |

IGNOREDGTFAMILY | Flag | Ignores the digital families. All nodes in which there are no analog terminals are considered to be digital. Default = YES. |

DGTDEFIOMODEL | I/O model | Default I/O model. Default = Generic I/O. |

DGTTFALL | Real | Default High-to-Low delay. Default = 2ns. |

DGTTRISE | Real | Default Low-to-High delay. Default = 2ns. |

DGTDELAY | Real | Default propagation delay. Default = 10ns. |

SLOWMODEDELAY | Integer | Slow-Mode delay (msec). Default = 1. |

Name | Type | Description |

TRANDEFCYCLES | Integer | Defines the number of cycles for the automatic setup of the transient analysis. Default = 5. |

TRANPTSXCYCLE | Integer | Defines the number of points per cycle for the automatic setup of the transient analysis. Default = 50. |

Name | Type | Description |

TNOM | Real | Sets the nominal temperature for which device models are created. TNOM can be overridden by a specification on any temperature dependent device model. Default = 27°C. |

TEMP | Real | Sets the actual operating temperature of the circuit. Any deviation from TNOM will produce a change in the simulation results. TEMP can be overridden by a temperature specification on any temperature dependent instance. Default = 27°C. |

KEEPOPINFO | Flag | Retains the operating point information when an AC Analysis is run. This is particularly useful if the circuit is large and you do not want to run a redundant Operating Point Analysis. Default=NO (run OP each time). |

MINBREAK | Real | Sets the minimum time between breakpoints. Default=0 seconds (sets the time automatically). |

SAVESUBCKT | Flag | If given, the internal subcircuit node voltages are also saved. Default = No. |