SLUSCC7C July 2016 – June 2018 TPS546C23
Use Equation 16 to calculate the value of the output inductor (L). The coefficient, KIND, represents the amount of inductor-ripple current relative to the maximum output current. The output capacitor filters the inductor-ripple current. Therefore, selecting a high inductor-ripple current impacts the selection of the output capacitor because the output capacitor must have a ripple-current rating equal to or greater than the inductor-ripple current. Generally, the KIND coefficient should be kept between 0.2 and 0.3 for balanced performance. Using this target ripple current, the required inductor size can be calculated as shown in Equation 16.
Selecting a value of 0.3 for the KIND coefficient, the target inductance, L, is 299 nH. Considering the variation and derating of the inductance and the 300-nH inductor, use Equation 17, Equation 18, and Equation 19 to calculate the inductor-ripple current (IRIPPLE), RMS current (IL(rms)), and peak current (IL(peak)), respectively. These values should be used to select an inductor with approximately the target inductance value, and current ratings that allow normal operation with some margin.
Considering the required inductance, RMS current, and peak current, the 300-nH inductor, SLC1480-301ML, from Coilcraft was selected for this application.