The MSEL1 pin programs USER_DATA_01 (COMPENSATION_CONFIG) and FREQUENCY_SWITCH. The resistor divider ratio for MSEL1 selects the nominal switching frequency. In the design procedure for MSEL1, switching frequency is configured first, then compensation is chosen after output capacitance is determined.

There is a trade-off between higher and lower switching frequencies for buck converters. Higher switching frequencies can produce smaller design size using lower valued inductors and smaller output capacitors compared to a power supply that switches at a lower frequency. However, the higher switching frequency causes extra switching losses, which decrease efficiency and impact thermal performance.

In this design, a moderate switching frequency of 550 kHz achieves both a small design size and a high-efficiency operation. Use the MSEL1 pin program table to select the frequency option. See Table 6-8 for resistor divider code selection. Resistor divider code 6 or 7 or open is needed to set the switching frequency to 550 kHz.