Virtuoso XL Layout Editor User Guide

Preparing Your Connectivity Source for the Virtuoso XL Layout Editor

For more details about using NLP expressions, see the Open Simulation System Reference Manual.

Analog Expression Language Expressions

AEL expressions, such as iPar and pPar, define the value of a parameter as a function of other instance parameters or parameters passed from other levels of hierarchy.

If you specify the value of a parameter using an AEL expression, the parameter

■Must be defined in thecomponent description format (CDF) for the cell of which the symbol is a view

■Must be a string for which parseAsNumber and parseAsCEL properties are set to yes

■Must not have a CDF callback (because the evaluation of the expression does not trigger the execution of the callback)

If Virtuoso XL detects a parameter value defined withiPar, pPar, or other AEL expressions not defined in the CDF, you see a warning in a message box.

For more information about AEL expressions, see “Scope of Parameters” in theCadence Analog Circuit Design Environment User Guide.

Simulation Design Variables

When you use simulation design variables to specify the value of a parameter in the circuit, Virtuoso XL uses the value last saved during the simulation of the circuit as the value for the layout implementation.

For more information about simulation design variables, see “Design Variables and Simulation” in Chapter 3 of the Cadence Analog Circuit Design Environment User Guide.

Using One-to-Many Mapping

You can implement one-to-many mapping in Virtuoso XL designs using

■Iterated instances and bus pins

■The multiplication factor (m-factor)

Virtuoso XL Layout Editor User Guide

Preparing Your Connectivity Source for the Virtuoso XL Layout Editor

■The series-connected factor (s-factor)

■One-to-Many Assignment with the Update Components and Nets Command

Iterated Instances and Bus Pins

You can use iterated instances and bus pins in a schematic with Virtuoso XL. Use of iterated instances enables one-to-many mapping between pins and devices in the schematic and multiple instances of the pins and devices in the layout.

For example, the figure below shows

■Bus pin SEL<0:1> in the schematic mapped to bus pins SEL<0> and SEL<1> in the layout

■Iterated instance K<0:1> mapped to instances IK(0)|P0, IK(0)|N0, IK(1)|P0, and IK(1)|N0 in the layout

Multiplication Factor (mfactor)

The multiplication factor (mfactor) is a parameter that defines a one-to-many parallel relationship between a device in a schematic and multiple instances of the device in the layout.

Virtuoso XL Layout Editor User Guide

Preparing Your Connectivity Source for the Virtuoso XL Layout Editor

The mfactor and mFactorSplit are hierarchical properties. Any instance in the connectivity source hierarchy can have these properties, and the multiplicity will be computed from the hierarchical path.

You can implement the mfactor as a CDF parameter or as a property of an instance or a cell. As a property of an instance or a cell, it can be a string, an integer, or a floating-point number.

You can use an environment variable, mfactorSplit, to control whether the mfactor produces multiple layout devices or not.

You can also add a Boolean property, lxMfactorSplit on a given instance to override the global value given by the mfactorSplit environment variable.

Note: You cannot use multiplication factors with components that cannot be used in parallel, such as voltage sources.

Series-Connection Factor (sfactor)

The series-connection factor (sfactor) is a parameter that can be used to define a one-to- many relationship between a device in a schematic and multiple instances in series connection in the layout. The sfactor property can be applied to two or three terminal resistors, capacitors, and inductors. You set the value of the sfactor property (called s or S, unless you change it in the Layout XL Options form) to the number of layout devices you

Virtuoso XL Layout Editor User Guide

Preparing Your Connectivity Source for the Virtuoso XL Layout Editor

want to generate. When you run the Gen from Source or Update Components and Nets command, Virtuoso XL generates the number of layout devices specified as the property value. It creates all the devices identical in size.

The sfactor can be a property only at the layout stop level. Any property above or below the layout stop level is ignored.

You can implement the sfactor as a CDF parameter or as a property of an instance or a cell. As a property of an instance or a cell, it can be an integer, a string, a floating-point number, or an expression.

You can use an environment variable, sfactorParam, to tell Virtuoso XL which parameter of the device is to be split. The default names of the parameters to be split are “r R” for resistor, “C c” for capacitor, and “l L” for inductor. You can set this environment variable from theLayout XL Options form.

Note: If both mfactor and sfactor are defined on the same instance,sfactor is ignored.

The lxSeriesTerms property must be defined on the instance in the schematic in order for Virtuoso XL to understand the connectivity of the devices with sfactor >1 and instance terminals>2. The description below shows setting the lxSeriesTerms PLUS and MINUS on

2 instance terminals.

lxSeriesTerms = “PLUS MINUS”

In the Layout XL Options form the Generate Multiple Instances option must be turned on.