Available Value Types

This topic provides descriptions of the available parameter value types for Nominal Optimization, Statistical Design, and Design of Experiments (DOE). For the procedures in which these value types are implemented, refer to the following topics:

• Performing Nominal Optimization
• Using Statistical Design
• Using Design of Experiments (DOE)

Value Types for Nominal Optimization

As described in the section, Specifying Component Parameters for Optimization, the Optimization tab of the Setup dialog box is used to enable or disable the optimization status of a parameter and to specify the type and format for the parameter range over which optimization is to take place.

In the Optimization tab, the Type drop-down list includes the following options:

Discrete Denotes a variable that is only allowed to take a specific list of values between a specified range. The range of discrete values is directly specified when you enter nominal value, minimum value, maximum value, and a step value. Notice that for this option, the Format drop-down list only includes min/max/step .

Note The discrete variable type is compatible only with the Random, Random Minimax, Random Max, Discrete, and Genetic optimization types. (Refer to the section, Available Optimizers. This variable type is ignored for all other nominal optimization methods, such as Gradient.

Continuous Denotes a variable that can be one of four types, which are selected from the Format drop down list, as follows:

• min/max Enables you to specify a nominal value, minimum value, and maximum value and to specify appropriate units for each.
• +/- Delta % Enables you to specify a nominal value and an appropriate unit for it, as well as Delta%.
• +/- Delta Enables you to specify a nominal value and an appropriate unit for it, as well as Delta.
• Unconstrained Enables you to specify only a nominal value and an appropriate unit for it. The range of values is constrained between zero and twice the initial nominal value automatically. Caution must be used when assigning this format to an item parameter. Many component parameters have a limited range for valid numeric assignment. Refer to your Advanced Design System Circuit Component manual for component parameter value limits.

The simple example in the following figure shows the difference between continuous and discrete type variables.

Continuous vs. Discrete Variables

Note that specifying continuous or discrete valued parts in your design has a direct impact on the type of optimizer that you can use in an optimization (see Available Optimizers); therefore, it is important to recognize and understand the difference before selecting an optimizer.

Value Types for Statistical Design

As described in the section, Specifying Component Parameters for Yield Analysis, the Statistics tab of the Setup dialog box is used to enable or disable the yield analysis status of a parameter and to specify the type and format for the parameter range over which yield analysis is to take place.

In the Statistics tab, the Type drop-down list includes the following options:

Gaussian Denotes a Gaussian distributed statistical variable that can be one of two types, which are selected from the Format drop-down list, as follows:

• +/- Std.Dev.% Specifies the +/- 1 sigma deviation range as a percentage of the nominal value.
• +/-Std.Dev. Specifies the +/- 1 sigma deviation value as an absolute value.

Uniform Denotes a variable that can be one of three types, which are selected from the Format drop down list, as follows:

• min/max Enables you to specify a nominal value, minimum value, and maximum value and to specify appropriate units for each.
• +/- Delta % Specifies the deviation range as a percentage of the nominal value.
• +/- Delta Specifies the deviation value as an absolute value.

Discrete Denotes a discrete uniform statistical variable. The set of discrete values is directly specified when you enter nominal value, minimum value, maximum value, and a step value. Notice that for this option, the Format drop-down list only includes min/max/step .

LogNormal Denotes a log-normal distributed statistical variable. A log-normal distribution is a probability distribution in which the logarithm of the parameter has a normal distribution. It is the minimum-information distribution for positive quantities with a given geometric mean and standard deviation. It is also the multiplicative analog of the bell curve. This variable can be one of two types, which are selected from the Format drop-down list, as follows:

• +/- Std.Dev.% Specifies the +/- 1 sigma deviation range as a percentage of the nominal value.
• +/-Std.Dev. Specifies the +/- 1 sigma deviation value as an absolute value.

Value Types for DOE

As described in the section, Specifying Component Parameters for DOE, the DOE tab of the Setup dialog box is used to enable or disable the DOE status of a parameter and to specify the type and format for the parameter range over which DOE is to take place.

In the DOE tab, the Type drop-down list includes the following options:

DOE Discrete Denotes a variable that can be one of three types, which are selected from the Format drop down list, as follows:

• min/max Enables you to specify a nominal value, minimum value, and maximum value and to specify appropriate units for each.
• +/- Delta % Specifies the deviation range as a percentage of the nominal value.
• +/- Delta Specifies the deviation value as an absolute value.