Issue link: https://resources.pcb.cadence.com/i/1532920
Purpose: To restrict the number of stubs on a trace's vias or on a net wiring topology to reduce signal reflections and maintain signal integrity. For high-speed designs, aim for zero or minimal stubs. When stubs are unavoidable, keep them as short as possible. Applies to: USB, HDMI, and any other high-speed interfaces that need minimal fanouts or stubs to operate efficiently. Importance: Affects current-carrying capacity and signal integrity Application: Power distribution, high-speed signals Steps: 1. Open the Constraint Manager (CM). Tip: As usual we will make a constraint set that holds the rules/constraints, then we apply that constraint set to a net, class, group or region. 2. Create an electrical constraint set under Electrical > Electrical Constraint Set > Routing > Wiring > Right click the DSN. 3. Choose Create - Electrical CSet… 4. Give the ECSet a name and it will be added to the spreadsheet. 5. Once added, enter a desired maximum stub length for the ECSet. 6. For example, let's say you want your stubs to be no more than 8 mils (0.203 mm), so you enter '8 mils' in the rule shown below for the SPIO_SCK signal constraint set. 7. Now you go to the following location to apply that constraint and stub rule it has: 8. In the CM, go to Net > Routing > Wiring. 9. Choose from the Referenced Electrical CSet column to set it to your desired net. 10. Notice how the stub length rule applies to the net, with added details like Max, Actual and Margin. Tip: Use to ensure tight signal integrity, and minimal reflections and antennas. 18 www.cadence.com OrCAD X Constraint Management Guide