Cadence Ebooks

IV. SIGNAL INTEGRITY AND HIGH-SPEED ROUTING Crosstalk is the unwanted electromagnetic coupling between traces on a printed circuit board (PCB) 25. Minimizing Crosstalk by Managing Parallelism and Trace Spacing Crosstalk - unwanted signal coupling between adjacent traces; can corrupt high- speed data, introduce jitter, degrade analog accuracy, and cause elusive, system-level bugs. It's a fundamental limitation of PCB geometry: electric and magnetic fields from one net can induce noise in its neighbors. As edge rates (rise/fall times) get faster and signal densities increase, crosstalk becomes a limiting factor in reliable, high-speed design. Careful control of parallelism and trace spacing is required to ensure signal integrity. When And Where To Apply Apply crosstalk management to all high- speed digital (clocks, data buses, SERDES), precision analog (ADC/DAC, sensor front- ends), and RF circuits, throughout layout and routing - especially on adjacent layers or where traces run in parallel over long distances.

• Cover
• I. Project Planning, Requirements, and Documentation
• 1.Establishing a Clean Design Rule Set
• 2. Preventing Floating or Unused Inputs and Outputs
• 3. Finalizing the PCB Stackup Early
• 4. Validating Symbol-to-Footprint Mapping
• 5. Using Descriptive Net and Component Naming
• 6. Confirming Component Availability and Avoiding Obsolete Parts
• 7. Archiving and Documenting the Complete Design for Future Reuse and Support
• II. Placement, Floorplanning, and Mechanical Integration
• 8. Including Mechanical References Early in the PCB Layout
• 9. Prioritizing Placement of Fixed and Critical Components
• 10. Planning BGA and Fine-Pitch Fanout Before Surrounding Placement
• 11. Grouping by Functional Blocks and Signal Flow
• 12. Respecting Assembly Spacing and Rework Access
• 13. Keeping Height and Keep-In/Keep-Out Constraints Visible
• 14. Reviewing Silkscreen and Markings for Readability and Clarity
• 15. Confirming Board Edge Clearances for Copper, Vias, and Components
• 16. Reviewing and Optimizing Via Types, Sizes, and Counts
• III. Power, Grounding, and Thermal
• 17. Using a Continuous Ground Plane
• 18. Optimizing Regulator and Power Converter Current Loops
• 19. Keeping Analog, Digital, and Power Domains Isolated
• 20. Preventing Ground Loops and Unintentional Return Paths
• 21. Pouring Copper with Electrical Intent, Not Just for Fill
• 22. Building Ground Via Fences and Edge Stitching
• 23. Managing Split Planes and Power Islands Correctly
• 24. Planning for Thermal Management: Heat Sinks, Vias, and Copper Pours
• IV. Signal Integrity and High-Speed Routing
• 25. Minimizing Crosstalk by Managing Parallelism and Trace Spacing
• 26. Routing Differential Pairs with Consistent Geometry and Return Paths
• 27. Avoiding Right-Angle and Acute Trace Corners
• 28. Minimizing Layer Transitions on Critical Nets
• 29. Eliminating Stubs and Dead-End Tees
• 30. Treating Length and Skew Matching as Numeric Constraints
• 31. Isolating Clocks, Resets, and Sensitive References from Noise Sources
• 32. Using Guard Traces and Shielding for Ultra-Sensitive or High-Speed Nets
• 33. Optimizing Decoupling and Bulk Capacitor Placement
• 34. Specifying Controlled Impedance and Reference Plane Requirements
• V. Manufacturability, Test, Reliability
• 35. Performing Design Rule Checks (DRC) and Electrical Rule Checks (ERC) Iteratively
• 36. Designing for Effective Test Point Access and Coverage
• 37. Verifying All Pad, Hole, and Footprint Sizes for Manufacturing
• 38. Specifying and Checking Solder Mask and Paste Mask Clearances
• 39. Reviewing Design for Manufacturability (DFM) and Assembly Constraints
• 40. Designing for Reliability in Harsh Mechanical, Thermal, and Environmental Conditions