11.1.1 Compact Layout for EMI Reduction

Radiated EMI is generated by the high di/dt components in pulsing currents in switching converters. The larger area covered by the path of a pulsing current, the more EMI is generated. High frequency ceramic bypass capacitors at the input side provide primary path for the high di/dt components of the pulsing current. Placing ceramic bypass capacitor(s) as close as possible to the VIN and PGND pins is the key to EMI reduction.

The SW pin connecting to the inductor must be as short as possible, and just wide enough to carry the load current without excessive heating. Use short, thick traces or copper pours (shapes) for high current conduction path to minimize parasitic resistance. The output capacitors must be placed close to the V_OUT end of the inductor and closely grounded to PGND pin and exposed PAD.

Place the bypass capacitors on VCC as close as possible to the pin and closely grounded to PGND and the exposed PAD.