8.2.2.2 Operating Frequency

The first step is to decide on a switching frequency for the regulator. There is a trade off between higher and lower switching frequencies. Higher switching frequencies may produce a smaller solution 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 additional switching losses, which negatively impact the converter’s efficiency and thermal performance. In this design, a moderate switching frequency of 480 kHz is selected to achieve both a small solution size and a high-efficiency operation. This frequency is set using the resistor at the RT/CLK pin (R3). Using Equation 17, the resistance required for a switching frequency of 480 kHz is 102 kΩ. A 100-kΩ resistor is used for this design.