7.3.1.3 Spread-Spectrum Mode

Systems with periodic switching signals may generate a large amount of switching noise in a set of narrowband frequencies (the switching frequency and its harmonics). The usual solution to reduce noise coupling is to add EMI-filters and shields to the boards. The register-selectable spread-spectrum mode of the device minimizes the need for output filters, ferrite beads, or chokes. In spread-spectrum mode, the switching frequency varies randomly by ±5% about the center frequency, reducing the EMI emissions radiated by the converter and associated passive components and PCB traces (see Figure 8). This feature is enabled with the CONFIG.EN_SPREAD_SPEC bit, and it affects all the buck converter cores.

Where a fixed frequency converter exhibits large amounts of spectral energy at the switching frequency, the spread spectrum architecture of the v spreads that energy over a large bandwidth.

Figure 8. Spread-Spectrum Modulation