Another method for reducing the overall radiated emissions in a buck converter is to bury problematic traces and surround them in copper ground plane. A portion of the VIN trace can be routed underneath the second ground layer. Effectively, this sandwiches this trace between the GND planes on layer 2 and 4, providing a makeshift faraday cage for the noise critical VIN signal. For applications that require longer power traces between the board supply and the buck converter this can result in a simple board noise filter. This technique can also be employed for the output voltage, but with lesser effects as this does not carry nearly as much of the energy from the high dv/dt switching loop.

In a similar vein to burying traces in the PCB, vias can be utilized to accomplish a similar effect. By surrounding noisy high potential lines with through-hole ground vias, the EMI of the trace can be effectively fenced off from the rest of the board. This interrupts any potential receiving antenna and provides low impedance paths to ground for the noise from the fenced traces. Both the VIN and VOUT power traces can be fenced off with ground vias, helping to keep any unintended antenna from radiating EMI. These are most effective with power traces that span multiple layers such as VIN and VOUT, essentially surrounding the VIN and VOUT traces entirely with GND.

Through the culmination of the careful routing of sensitive signals, a snubber circuit, and PCB layout techniques, the TPSM33620-Q1 passes the CISPR25 radiated EMI standard. Figure 3-8, Figure 3-9, and Figure 3-10 represent the measured peak and average radiated EMI performance of the TPSM33620-Q1 spanning the 150kHz to 1GHz range.