SLOA343 August   2024 TPS543820 , TPS543A22 , TPSM843620 , TPSM843A22

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Layout Techniques to Reduce EMI
    1. 2.1 Placement of Passive Components
    2. 2.2 Ground Flooding
    3. 2.3 Minimize Number of Antennas
    4. 2.4 Via Stitching
    5. 2.5 Additional Steps to Minimize Impedance or Noise
  6. 3Designing for EMI-Optimized Layout
  7. 4Test Results for Radiated Interference
  8. 5EMI Filtering
  9. 6Summary
  10. 7References

Placement of Passive Components

Placing decoupling capacitors as close to the IC as possible is highly recommended in any power supply to minimize noise. This can reduce the distance that the high frequency currents have to travel, and can therefore minimize the loop antenna area that these frequencies can radiate through.

For output passive components, placing the highest frequency output capacitor close to the output side of the inductor can help to minimize ringing at the source. The farther away capacitors are away from the inductor, the more series resistance is introduced, and the less impact this can have to filter the high frequency switching noise. With this, larger capacitors need to be placed further away while the smaller capacitors need to be prioritized, as they typically have less equivalent series resistance (ESR).