Issue link: https://resources.pcb.cadence.com/i/1534337
f Solution: Set up controlled impedance routing for critical signals, especially single-ended and differential pairs, using the Constraint Manager. By defining impedance targets for high-speed traces, you ensure impedance consistency and reduce reflections. f Implementation Steps: ɢ In Constraint Manager, set impedance values for each high-speed net. ɢ ○Use the Length Tuning tool to keep trace lengths within acceptable ranges, as reflections are also affected by excessive trace length and mismatched signal paths. Crosstalk Between Traces Diagram illustrating crosstalk between two traces running parallel to each other. f Problem: Crosstalk is the unintended coupling of signals between adjacent traces, causing noise and signal interference. This issue is more pronounced in densely packed PCBs with high-frequency signals, as electromagnetic fields from one trace can easily affect another. f Solution: Define trace spacing rules in Constraint Manager to maintain adequate distance between high-speed traces. Additionally, use differential pair routing for noise-sensitive signals, ensuring spacing between pairs is consistent to minimize coupling. f Implementation Steps: ɢ In Constraint Manager, set minimum spacing requirements for high-speed nets, especially those prone to crosstalk. ɢ For differential pairs, apply consistent spacing and length matching to reduce interference and signal distortion. Practical Tips for Mitigating Reflections and Crosstalk f Use Ground Planes for Shielding: Place critical high-speed signals adjacent to a continuous ground plane to shield them from interference. Ground planes help contain electromagnetic fields and reduce the risk of coupling. f Minimize Stub Lengths: Stubs, or unused segments of a trace, can act as antennas and introduce reflections. Avoid creating stubs, especially on high-speed nets, or keep them as short as possible. f Simulate and Analyze: Utilize simulation tools to assess the impact of crosstalk and reflections before finalizing the layout. Simulations allow you to visualize potential interference points and validate the effectiveness of spacing and impedance settings. 8 www.cadence.com OrCAD X High-Speed Digital Design Guide