SLVSAF1E October 2010 – May 2019 TPS54388-Q1
The first step is to decide on a switching frequency for the regulator. Typically, one would choose the highest switching frequency possible 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 hurt the converter performance. The converter is capable of running from 200 kHz to 2 MHz. Unless a small solution size is an ultimate goal, select a moderate switching frequency of 1 MHz to achieve both a small solution size and high-efficiency operation. Using Equation 8, calculate R5 to be 180 kΩ. Choose a standard 1% 182-kΩ value for the design.