EMA Academy

PCB Walk-through 4: Constraints

OrCAD PCB 17.4 Walk-Through PCB Walk-through 4: Constraints

This walk-through demonstrates how to set up differential pairs and constraints using OrCAD PCB Designer Professional. After you complete this topic, you will be able to:

Set up a differential pair
Specify electrical, physical and differential pair rules with Constraint Sets

To follow along, continue working with the design completed in PCB Walkthrough 3 or open the provided board file in the folder directory, PCB Walkthrough 4_Constraints.

Open in New Window

Note: If you did not define your differential pairs at the schematic level, use the following steps for definition in the PCB:

Select Setup > Add Differential Pairs from the menu.

Select Auto Generate.

Assign DP_ for the name.

Set the + polarity to +.

Set the – polarity to –.

Click Generate.

Click OK to close the window.

This has generated the differential pair.

In the Design Workflow, select Constraints > Modes.

Note: In the Modes window, select which constraints will be checked by setting the constraints “On” or “Off”. Electrical constraints are available in OrCAD PCB Designer Professional.

Close the Mode window.

In the Design Workflow, select Constraints > Physical.

Note: This opens the constraint manager window. In the constraint manager, you can assign electrical, physical, and spacing constraints. Assign constraints by creating Csets or assigning values to each individual net.