An EMC review connects a noise source to a coupling path and a susceptible or radiating structure. Consider the PCB together with its cables, enclosure and power connections. A layout change should address an identified mechanism; adding filters or stitching vias without a defined current path can create work without resolving the failure.
Map sources and sensitive regions
Identify switching nodes, fast edges, oscillators, power loops and sensitive analog or radio sections. Review operating modes, including startup and burst behavior. Place and route with those interactions in mind before the layout becomes too constrained to change.
Control current-loop geometry
Follow outgoing and returning current paths for the important high-frequency loops. TI’s converter-layout guidance explains how loop geometry and reference structures affect emissions. Apply the relevant device guidance to the actual topology instead of assuming every ground split or large copper pour improves EMC.
Treat external connections as system boundaries
Cables and enclosure openings can become coupling paths. Review filter placement, shield connections, ESD paths and chassis relationships with the mechanical design. Keep the intended high-frequency connection understandable in both the schematic and the physical assembly.
Use measurements to isolate causes
During pre-compliance work, record the operating mode, cable arrangement, enclosure state and instrument setup. Change one variable at a time and compare results. A bench improvement under a different configuration may not carry into the formal test setup.
Example: emissions change when a cable is attached
Compare the same operating mode with controlled cable placement, then investigate how common-mode current reaches that cable. Inspect the connector region and return paths before adding a filter randomly elsewhere on the board. Preserve the test configuration so the effect of each change can be reproduced.
Design review checklist
- Map dominant sources and coupling paths.
- Review reference continuity and switching loops.
- Include cables, shielding and enclosure contacts.
- Use the applicable product test requirements and a reproducible setup.
Primary reference
Consult the device vendor’s layout guidance and validate the assembled system. TI converter EMI layout application note.