8.2.2.1 Step One: Select the Switching Frequency

Choose the highest switching frequency possible in order to produce 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 in turn decrease the device performance. The device is capable of operating between 200 kHz and 2 MHz. Select a moderate switching frequency of 1 MHz in order to achieve both a small solution size and a high-efficiency operation. Using Equation 5, R4 is calculates to 180 kΩ. A standard 1%, 182-kΩ resistor is used in the design.