7.3.2 Input Capacitor Selection

The TPSM84209 requires a ceramic input capacitor with a minimum effective capacitance of 10 μF. Use only high-quality ceramic type X5R or X7R capacitors with sufficient voltage rating. An additional 47 µF of non-ceramic capacitance is recommended for applications with transient load requirements. The voltage rating of input capacitors must be greater than the maximum input voltage. To compensate for the derating of ceramic capacitors, TI recommends a voltage rating of twice the maximum input voltage. At worst case, when operating at 50% duty cycle and maximum load, the combined ripple current rating of the input capacitors must be at least 1.25 Arms. Table 2 includes a preferred list of capacitors by vendor.