SNAA408 April   2025 LMK3H0102

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Output Recommendations
    1. 2.1 Differential vs. Single-Ended
    2. 2.2 Slew Rate
    3. 2.3 Spread Spectrum Clocking
  6. 3PCB Design
    1. 3.1 Stackup
    2. 3.2 Power Filtering
    3. 3.3 Avoid Bottlenecking
    4. 3.4 Strategic Via Placements
      1. 3.4.1 Distributing Power Concentrations
        1. 3.4.1.1 Via Sizes
        2. 3.4.1.2 Pads and Pours
      2. 3.4.2 Shielding and Stitching Vias
  7. 4Minimize Possible Antennas
    1. 4.1 Stubs
    2. 4.2 Net Pours
  8. 5Summary
  9. 6References

3.4.1.1 Via Sizes

Running a trace through a via causes a disruption in the current flow, which is likely to cause an EMI spike. However, having vias significantly larger than the trace width creates an even harsher transition (Figure 1-1). This harsher transition can act as an antenna, creating larger EMI spurs. When running a trace through a via, have the trace width be slightly larger than the via (Figure 3-7).

Passive with Narrow Trace to Ground ViaFigure 3-6 Passive with Narrow Trace
to Ground Via

Passive with Wider Trace to Ground Via

Figure 3-7 Passive with Wider Trace
to Ground Via