ABSTOL = x

Sets the absolute node voltage error tolerance for DC and transient analysis. Decrease ABSTOL if accuracy is more important than convergence time.

CAPTAB

Prints table of single plate nodal capacitance for diodes, BJTs, MOSFETs, JFETs and passive capacitors at each operating point.

CSHDC

The same option as CSHUNT, but is used only with option CONVERGE.

DCCAP

Used to generate C-V plots and to print out the capacitance values of a circuit (both model and element) during a DC analysis. C-V plots are often generated using a DC sweep of the capacitor. Default = 0 (off).

DCFOR = x

Used in conjunction with the DCHOLD option and the .NODESET statement to enhance the DC convergence properties of a simulation. DCFOR sets the number of iterations that are to be calculated after a circuit converges in the steady state. Since the number of iterations after convergence is usually zero, DCFOR adds iterations (and computational time) to the calculation of the DC circuit solution. DCFOR helps ensure that a circuit has actually, not falsely, converged. Default = 0.

DCHOLD = x

DCFOR and DCHOLD are used together for the initialization process of a DC analysis. They enhance the convergence properties of a DC simulation. DCFOR and DCHOLD work together with the .NODESET statement. The DCHOLD option specifies the number of iterations a node is to be held at the voltage values specified by the .NODESET statement. The effects of DCHOLD on convergence differ according to the DCHOLD value and the number of iterations needed to obtain DC convergence.

If a circuit converges in the steady state in fewer than DCHOLD iterations, the DC solution includes the values set by the .NODESET statement. However, if the circuit requires more than DCHOLD iterations to converge, the values set in the .NODESET statement are ignored and the DC solution is calculated with the .NODESET fixed source voltages open circuited. Default = 1.

DCSTEP = x

Used to convert DC model and element capacitors to a conductance to enhance DC convergence properties. The value of the element capacitors are all divided by DCSTEP to obtain a DC conductance model.
Default = 0 (seconds).

DV = x

The maximum iteration-to-iteration voltage change for all circuit nodes in both DC and transient analysis. Values of 0.5 to 5.0 can be necessary for some high-gain bipolar amplifiers to achieve a stable DC operating point. CMOS circuits frequently require a value of about 1 volt for large digital circuits. Default = 1000 (or 1e6 if DCON = 2).

GRAMP = x

Value is set by Star-Hspice during the autoconvergence procedure. GRAMP is used in conjunction with the GMINDC convergence control option to find the smallest value of GMINDC that results in DC convergence. GMINDC is described in Convergence Control Option Descriptions.

GRAMP specifies the conductance range over which GMINDC is to be swept during a DC operating point analysis. Star-Hspice substitutes values of GMINDC over this range and simulates at each value. It then picks the lowest value of GMINDC that resulted in the circuit converging in the steady state.

If GMINDC is swept between 1e-12 mhos (the default) and 1e-6 mhos, GRAMP is set to 6 (the value of the exponent difference between the default and the maximum conductance limit). In this case, GMINDC is first set to 1e-6 mhos, and the circuit is simulated. If convergence is achieved, GMINDC is next set to 1e-7 mhos, and the circuit is simulated again. The sweep continues until a simulation has been performed at all values on the GRAMP ramp. If the combined conductance of GMINDC and GRAMP is greater than 1e-3 mho, a false convergence can occur. Default = 0.

GSHUNT

Conductance added from each node to ground. The default value is zero. Add a small GSHUNT to each node to possibly solve "Timestep too small" problems caused by high frequency oscillations or by numerical noise .

ICSWEEP

For a parameter or temperature sweep, saves the results of the current analysis for use as the starting point in the next analysis in the sweep. When ICSWEEP = 1, the current results are used in the next analysis. When ICSWEEP = 0, the results of the current analysis are not used in the next analysis. Default = 1.

ITL1 = x

Sets the maximum DC iteration limit. Increasing this value is unlikely to improve convergence for small circuits. Values as high as 400 have resulted in convergence for certain large circuits with feedback, such as operational amplifiers and sense amplifiers. Something is usually wrong with a model if more than 100 iterations are required for convergence. Set .OPTION ACCT to obtain a listing of how many iterations are required for an operating point. Default = 200.

ITL2 = val

Sets the DC transfer curve iteration limit. Increasing the iteration limit can be effective in improving convergence only on very large circuits. Default = 50.

KCLTEST

Activates the KCL test (Kirchhoff's Current Law) function. This test results in a longer simulation time, especially for large circuits, but provides a very accurate check of the solution. Default = 0.

When set to 1, Star-Hspice sets the following options:

RELMOS and ABSMOS options are set to 0 (off).

ABSI is set to 1e-16 A.

RELI is set to 1e-6.

To satisfy the KCL test, the following condition must be satisfied for each node:

where the ibs are the node currents.

MAXAMP = x

Sets the maximum current through voltage defined branches (voltage sources and inductors). If the current exceeds the MAXAMP value, an error is issued. Default = 0.0.

NEWTOL

Calculates one more iterations past convergence for every DC solution and timepoint circuit solution calculated. When NEWTOL is not set, once convergence is determined, the convergence routine is ended and the next program step begun. Default = 0.

NOPIV

Prevents Star-Hspice from switching automatically to pivoting matrix factorization when a nodal conductance is less than PIVTOL. NOPIV inhibits pivoting. Also see PIVOT.

OFF

Initializes the terminal voltages of all active devices to zero if they are not initialized to other values. For example, if the drain and source nodes of a transistor are not both initialized using .NODESET or .IC statements or by connecting them to sources, then the OFF option initializes all of the nodes of the transistor to zero. The OFF option is checked before element IC parameters, so if an element IC parameter assignment exists for a particular node, the node is initialized to the element IC parameter value even if it was previously set to zero by the OFF option. (The element parameter OFF can be used to initialize the terminal voltages to zero for particular active devices).

The OFF option is used to help find exact DC operating point solutions for large circuits.

PIVOT = x

Provides different pivoting algorithm selections. These can be used effectively to reduce simulation time and achieve convergence in circuits that produce hard-to-solve matrix equations. The pivot algorithm is selected by setting PIVOT to one of the following values:

• 0 Original nonpivoting algorithm
• 1 Original pivoting algorithm
• 2 Pick largest pivot in row algorithm
• 3 Pick best in row algorithm
• 10 Fast nonpivoting algorithm, more memory required
• 11 Fast pivoting algorithm, more memory required than for PIVOT values less than 11

• 12 Pick largest pivot in row algorithm, more memory required than for PIVOT values less than 12
• 13 Fast best pivot: faster, more memory required than for PIVOT values less than 13

Default = 10.

The fastest algorithm is PIVOT = 13, which can improve simulation time by up to ten times on very large circuits. However, the PIVOT = 13 option requires substantially more memory for the simulation. Some circuits with large conductance ratios, such as switching regulator circuits, might need pivoting. If PIVTOT = 0, Star-Hspice automatically changes from nonpivoting to a row pivot strategy upon detection of any diagonal matrix entry less than PIVTOL. This strategy provides the time and memory advantages of nonpivoting inversion, while avoiding unstable simulations and incorrect results. Use .OPTION NOPIV to prevent pivoting from being used under any circumstances.

For very large circuits, PIVOT = 10, 11, 12, or 13 can require excessive memory.

If Star-Hspice switches to pivoting during a simulation, the message "pivot change on the fly" is printed, followed by the node numbers causing the problem. Use .OPTION NODE to obtain a node-to-element cross reference.

SPARSE is the same as PIVOT.

PIVREF

Pivot reference. Used in PIVOT = 11, 12, 13 to limit the size of the matrix. Default = 1e+8.

PIVREL = x

Sets the maximum/minimum row/matrix ratio. Use only for PIVOT = 1. Large values for PIVREL can result in very long matrix pivot times. If the value is too small, however, no pivoting occurs. It is best to start with small values of PIVREL, using an adequate but not excessive value for convergence and accuracy. Default = 1E-20 (max = 1e-20, min = 1).

PIVTOL = x

Sets the absolute minimum value for which a matrix entry is accepted as a pivot. PIVTOL is used as the minimum conductance in the matrix when PIVOT = 0. Default = 1.0e-15.

RESMIN = x

Specifies the minimum resistance value for all resistors, including parasitic and inductive resistances. Default = 1e-5 (ohm). Range: 1e-15 to 10 ohm.

SPARSE = x

Provides different pivoting algorithm selections. These can be used effectively to reduce simulation time and achieve convergence in circuits that produce hard-to-solve matrix equations. The pivot algorithm is selected by setting PIVOT to one of the following values:

• 0 Original nonpivoting algorithm
• 1 Original pivoting algorithm
• 2 Pick largest pivot in row algorithm
• 3 Pick best in row algorithm
• 10 Fast nonpivoting algorithm, more memory required
• 11 Fast pivoting algorithm, more memory required than for PIVOT values less than 11
• 12 Pick largest pivot in row algorithm, more memory required than for PIVOT values less than 12
• 13 Fast best pivot: faster, more memory required than for PIVOT values less than 13

Default = 10.

The fastest algorithm is PIVOT = 13, which can improve simulation time by up to ten times on very large circuits. However, the PIVOT = 13 option requires substantially more memory for the simulation. Some circuits with large conductance ratios, such as switching regulator circuits, might need pivoting. If PIVTOT = 0, Star-Hspice automatically changes from nonpivoting to a row pivot strategy upon detection of any diagonal matrix entry less than PIVTOL. This strategy provides the time and memory advantages of nonpivoting inversion, while avoiding unstable simulations and incorrect results. Use .OPTION NOPIV to prevent pivoting from being used under any circumstances.

For very large circuits, PIVOT = 10, 11, 12, or 13 can require excessive memory.

If Star-Hspice switches to pivoting during a simulation, the message "pivot change on the fly" is printed, followed by the node numbers causing the problem. Use .OPTION NODE to obtain a node-to-element cross reference.

SPARSE is the same as PIVOT.

CSCAL

Sets the capacitance scale. Capacitances are multiplied by CSCAL. Default = 1e+12.

FMAX

Sets the limit for maximum pole and zero frequency value.
Default = 1.0e+12 · FSCAL.

FSCAL

Sets the frequency scale. Frequency is multiplied by FSCAL. Default = 1e-9.

GSCAL

Sets the conductance scale. Conductances are multiplied by GSCAL. Resistances are divided by GSCAL. Default = 1e+3.

ITLPZ

Sets the pole/zero analysis iteration limit. Default = 100.

LSCAL

Sets inductance scale. Inductances are multiplied by LSCAL. Default = 1e+6.

The scale factors must satisfy the following relations:

If scale factors are changed, it might be necessary to modify the initial Muller points (X0R, X0I), (X1R, X1I) and (X2R, X2I), even though Star-Hspice multiplies initial values by (1e-9/GSCAL).

PZABS

Sets absolute tolerances for poles and zeros. This option affects the low frequency poles or zeros. It is used as follows:

If ,

then and .

It is also used for convergence tests. Default = 1e-2.

PZTOL

Sets the relative error tolerance for poles or zeros. Default = 1.0e-6.

RITOL

Sets the minimum ratio value for (real/imaginary) or (imaginary/real) parts of the poles or zeros. RITOL is used as follows:

If , then

If , then

Default = 1.0e-6.

(X0R,X0I),


(X1R,X1I),
(X2R,X2I)

The three complex starting points in the Muller pole/zero analysis algorithm are:

X0R = -1.23456e6 X0I = 0.0

X1R = -1.23456e5 X1I = 0.0
X2R = +.23456e6 X2I = 0.0

These initial points are multiplied by FSCAL.