PCB Stack-Up, Grounding and EMI Essentials

Stack-up fundamentals

A common four-layer arrangement places signals on the outer layers with a solid ground plane and a power layer inside. Close coupling between signal layers and a ground reference minimises loop area and radiation.

Grounding strategy

For most mixed-signal boards, a single continuous ground plane with careful component partitioning works better than split grounds. Analog and digital sections are kept physically apart so that their return currents do not overlap.

Controlling emissions

• Keep fast edges no faster than needed
• Route clocks short and over solid reference
• Filter and decouple at every supply entry
• Avoid traces along board edges

Improving immunity

Interfaces leaving the board are the main entry points for disturbances. Filtering, TVS protection and proper shield termination at connectors keep external energy from reaching sensitive circuitry.