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EVM Assembly Drawings and Layout Guidelines
13
SLUUBJ1A – February 2017 – Revised June 2017
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Copyright © 2017, Texas Instruments Incorporated
TPS2373-4EVM-758 Evaluation Module
7.3
EMI Containment
The following guidelines are provided for EMI containment:
•
Use compact loops for dv/dt and di/dt circuit paths (power loops and gate drives).
•
Use minimal, yet thermally adequate, copper areas for heat sinking of components tied to switching
nodes (minimize exposed radiating surface).
•
Use copper ground planes (possible stitching) and top-layer copper floods (surround circuitry with
ground floods).
•
Use a 4-layer PCB, if economically feasible (for better grounding).
•
Minimize the amount of copper area associated with input traces (to minimize radiated pickup).
•
Hide copper associated with switching nodes under shielded magnetics, where possible.
•
Heat sink the quiet side of components instead of the switching side, where possible (like the output
side of inductor).
•
Use Bob Smith terminations, Bob Smith EFT capacitor, and Bob Smith plane.
•
Use Bob Smith plane as ground shield on the input side of the PCB (creating a phantom or literal earth
ground).
•
Use LC filter at DC/DC input.
•
Dampen high-frequency ringing on all switching nodes, if present (allow for possible snubbers).
•
Control rise times with gate-drive resistors and possibly snubbers.
•
Switching frequency considerations
•
Use of EMI bridge capacitor across isolation boundary (isolated topologies).
•
Observe the polarity dot on inductors (embed noisy end).
•
Use of ferrite beads on input (allow for possible use of beads or 0-
Ω
resistors).
•
Maintain physical separation between input-related circuitry and power circuitry (use ferrite beads as
boundary line).
•
Balance efficiency versus acceptable noise margin.
•
Possible use of common-mode inductors.
•
Possible use of integrated RJ-45 jacks (shielded with internal transformer and Bob Smith terminations).
•
End-product enclosure considerations (shielding).