The most critical parameters for the inductor are the inductance, peak current, and the DC resistance. The inductance is related to the peak-to-peak inductor ripple current, the input, and the output voltages. Because the ripple current increases with the input voltage, the maximum input voltage is always used to determine the inductance. To calculate the minimum value of the output inductor, use Equation 1. A reasonable value for the ripple current is 40% (K_IND) of the DC output current. For this design example, the minimum inductor value is calculated to be 20.4 µH, and a nearest standard value was chosen: 22 µH. For the output filter inductor, it is important that the RMS current and saturation current ratings not be exceeded. The RMS and peak inductor current can be found in Equation 3 and Equation 4. The inductor ripple current is 0.22 A, and the RMS current is 0.6 A. As the equation set demonstrates, lower ripple currents reduce the output voltage ripple of the regulator but require a larger value of inductance. A good starting point for most applications is 22 μH with a 1.6-A current rating. Using a rating near 1.6 A enables the LV2862 to current limit without saturating the inductor. This is preferable to the LV2862 going into thermal shutdown mode and the possibility of damaging the inductor if the output is shorted to ground or other long-term overload.

Equation 2.

Equation 3.

Equation 4.

Equation 5.