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EVM Assembly Drawings and Layout Guidelines

7.3 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 4-layer PCB, if economically feasible (for better grounding)

• Minimize the amount of copper area associated with input traces (minimizing 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 a ground shield on the input side of the PCB (creating a phantom or literal

earth ground)

• Use an LC filter at the 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 an EMI bridge capacitor across isolation boundary (isolated topologies)

• Observe the polarity dot on inductors (embed noisy end)

• Use 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 vs 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)

SLVU753–July 2012 TPS23752EVM-145: Evaluation Module for TPS23752

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