8.2.2.2 Step One: Select the Switching Frequency

The first step is to decide on a switching frequency for the regulator. Typically, you want to choose the highest switching frequency possible because this produces the smallest solution size. The high-switching frequency allows for lower valued inductors and smaller output capacitors compared to a power supply that switches at a lower frequency. However, the highest switching frequency causes extra switching losses, which hurt the the performance of the converter. The converter is capable of running from 300 kHz to 2 MHz. Unless a small solution size is an ultimate goal, a moderate switching frequency of 1 MHz is selected to achieve both a small solution size and a high-efficiency operation. Using Equation 9, R4 is calculated to be 180 kΩ. A standard 1% 182-kΩ value was chosen in the design.