A low ESR ceramic capacitor is needed between the VIN pin and ground pin. This capacitor prevents large voltage transients from appearing at the input. Use a 1-µF to 10-µF value with X5R or X7R dielectric. Depending on construction, a ceramic capacitor value can decrease up to 50% of the nominal value when rated voltage is applied. Consult with the capacitor manufactures data sheet for information on capacitor derating over voltage and temperature. The capacitor must also have a ripple current rating greater than the maximum input current ripple of the LMR14010A. The input ripple current can be calculated using below Equations.

For this example design, one 2.2-µF, 50-V capacitor is selected. The input capacitance value determines the input ripple voltage of the regulator. The input voltage ripple can be calculated using Equation 10. Using the design example values, I_OUTMAX = 1 A, C_IN = 2.2 µF, ƒ_SW = 700 kHz, yields an input voltage ripple of 162 mV and an rms input ripple current of 0.5 A.

Equation 9.

Equation 10.