8.1.3 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 14. Inductor Current Waveform

To keep the circuit in continuous conduction mode (CCM), the maximum ripple current I_RIPPLE should be less than twice the minimum load current, or 0.2 Ap-p. Using this value of ripple current, the value of inductor (L1) is calculated using the following:

Equation 6.

Equation 7.

This procedure provides a guide to select the value of L1. The nearest standard value (100 µH) will be 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 0.7 A nominal (0.85 A maximum). The selected inductor (see Table 1) has a conservative 1.0 Amp saturation current rating. For this manufacturer, the saturation rating is defined as the current necessary for the inductance to reduce by 30%, at 20°C.