Virtuoso XL Layout Editor User Guide

Generating Your Layout with Virtuoso XL Layout Editor

Note: When placing components within the design boundary, the Place As In Schematic command might cause the components to overlap, resulting in shorts. When you create a short, Virtuoso XL displays a marker over the short.

Virtuoso XL does not compact the layout, so the placement of components might not meet

Design Rule Checker (DRC) or other design requirements.

Constraints entered using the Constraint Manager are not observed by the Place As In

Schematic command.

Moving Components from the Schematic into the Layout (Pick from Schematic)

To place devices and/or pins directly from the schematic into the layout use the Create-Pick from Schematic command. If your connectivity reference is not a schematic, you cannot use this command.

Placing a Group of Schematic Elements Together

Use the Group As In Schematic option to place the instance/pins in the layout with the same relative position as in the schematic.

1.From the layout window, choose Create – Pick from Schematic.

The first time you open a new design and use this command, theDefine Connectivity Reference form appears.

2.If the Define Connectivity Reference form appears, type the library, cell, and view name of the schematic from which you want to pick elements to place in the layout (if this information is different from the information that appears by default in the form) and click

OK.

3.In the Pick from Schematic form, turn on Group As In Schematic. In this mode, you cannot change the parameters of the components.

4.Select a group of components (or all the components) in the schematic.

5.If some components in the schematic are already present in the layout, you cannot select them; only those components not yet placed can be selected.

Virtuoso XL Layout Editor User Guide

Generating Your Layout with Virtuoso XL Layout Editor

The Pick from Schematic form appears.

6.Turn on the options you want.

Draglines displays rubberbanding lines that connect pins of the object you are moving to pins of the nearest objects.

Constraint Assisted allows objects to be moved only in ways that satisfy the constraints entered using the Constraint Manager, once the object has satisfied the constraint.

Transistor Chaining allows MOS transistors (or fingers of folded transistors) to be automatically abutted to form a stack.

Transistor Folding allows MOS transistors to be automatically divided into fingers for optimum area usage.

NMOS Fold Threshold lets you type in the maximum size of the folded NMOS transistor. This value defaults to the lxMaxWidth value set on the connectivity source component.

Changing this value overwrites the lxMaxWidth value you entered in the Edit Component Type form.

Virtuoso XL Layout Editor User Guide

Generating Your Layout with Virtuoso XL Layout Editor

PMOS Fold Threshold lets you type in the maximum size of the folded PMOS transistor. This value defaults to the lxMaxWidth value set on the connectivity source component.

Changing this value overwrites the lxMaxWidth value you entered in the Edit

Component Type form.

7.To see a list of the components in the schematic that are not yet placed in the layout, click

Unplaced.

The Pick from Schematic Instance/Pin List appears.

8.In the list box, click on the names of the devices you want to place and click Apply or OK.

9.Move the cursor into the layout window and click.

The group of components selected are placed in the layout in the same relative position as in the schematic.

Virtuoso XL Layout Editor User Guide

Generating Your Layout with Virtuoso XL Layout Editor

Only components not yet present in the layout can be placed.

Placing Individual Components

To place individual components from the schematic in the layout, follow these steps.

1.In the Pick from Schematic form, turn on Place Individually.

The Pick from Schematic form changes to let you select individual instances.

Virtuoso XL Layout Editor User Guide

Generating Your Layout with Virtuoso XL Layout Editor

Note: The Place Individually option does not allow you to chain devices. Transistor

Chaining is only available with the Group As In Schematic option.

2.In the schematic, click on the component or group of components you want to place in the layout.

To select multiple components, click on the first object to select it andShift click on the other objects or click and drag over the objects. You can deselect objects with Control click.

Selected objects in the schematic remain highlighted until they are deselected or placed in the layout.

You cannot select objects in the schematic if objects with the same name are already present in the layout.

3.To automatically fold MOS devices into divided fingers for optimum are usage turn on the

Transistor Folding option.

NMOS Fold Threshold lets you type in the maximum size of the folded NMOS transistor. This value defaults to the lxMaxWidth value set on the connectivity source component.

PMOS Fold Threshold lets you type in the maximum size of the folded PMOS transistor. This value defaults to the lxMaxWidth value set on the connectivity source component.

Important

When the Transistor Folding option is turned on the device properties do not appear at the bottom of the Pick from Schematic form. If you need to update any of the device properties turn off Transistor Folding.

4.Select Unplaced to view the Pick from Schematic Instance/Pin List. Select the pin or instance and click Apply. The pin or instance will be selected in the schematic window.

5.Move the cursor into the layout window and the Pick from Schematic form updates with the Library, Cell, View, and InstName.

The Pick from Schematic form updates to show the parameters associated with the component currently being placed.

6.The component to be placed first is highlighted in the schematic in the color assigned to the hilite drawing2 layer. Selected instances that have not yet been placed are highlighted in the color assigned to the hilite drawing layer.

The outline of the component follows the cursor in the layout. Rubberbanding drag lines, showing connectivity to already placed components, follow the component outline.