SNVSAT4A September 2017 – June 2021 LP873220-Q1
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 LP873220-Q1 has a register-selectable spread-spectrum mode which minimizes the need for output filters, ferrite beads, or chokes. In spread spectrum mode, the switching frequency varies around the center frequency, reducing the EMI emissions radiated by the converter and associated passive components and PCB traces (see Figure 7-2). Spread-spectrum mode is only available when an internal RC oscillator is used (EN_PLL bit is 0 in PLL_CTRL register), it is enabled with the EN_SPREAD_SPEC bit in the CONFIG register, and it affects both buck cores.