8.2.2.4 L1

The inductor value is determined based on the operating frequency, load current, ripple current, and the minimum and maximum input voltage (V_IN(min), V_IN(max)).

Figure 17. Inductor Current Waveform

To keep the circuit in CCM, the maximum ripple current I_RIPPLE must be less than twice the minimum load current, or 0.4 Ap-p. Using this value of ripple current, the value of inductor (L1) is calculated using Equation 8 and Equation 9:

Equation 8.

Equation 9.

This procedure provides a guide to select the value of L1. The nearest standard value (47 µH) is used. L1 must be rated for the peak current (I_PK+) to prevent saturation. During normal loading conditions, the peak current occurs at maximum load current plus maximum ripple. During an overload condition, the peak current is limited to 2.1 A nominal (2.5 A maximum). The selected inductor has a conservative 3.25-Amp saturation current rating. The saturation rating is defined by inductor manufacturers as the current necessary for the inductance to reduce by 30%, at 20°C.