8.2 Inductor Selection and Slope Compensation

When selecting an inductor for the MCP16367/8/9, key parameters to consider include inductance value, RMS current rating, saturation current, and DC resistance (DCR).

The inductance value is especially important for ensuring stable operation. For duty cycles above 50%, internal slope compensation is applied based on the output voltage and the input-to-output voltage ratio to maintain current loop stability.

To achieve the appropriate amount of slope compensation, it is recommended to keep the inductor down-slope current constant by adjusting the inductance value in relation to V_OUT.

The inductor RMS current rating indicates the current level at which the inductor’s temperature increases by +20°C to +40°C, depending on the manufacturer’s specifications. The saturation current is defined as the peak current at which the inductor’s inductance decreases by 10% to 30%, also depending on the manufacturer. For reliable operation, ensure that both the nominal and peak currents in your application remain well within the inductor’s specified RMS and saturation current ratings

The peak inductor current can be calculated with Figure   1.

Where:

When choosing the inductor, sufficient design margin must be taken into account to prevent the inductor from entering deep saturation. Overcurrent conditions must also be taken into account, especially at high input voltages where inductor current rise rapidly