When the switch is enabled, the output capacitors must be charged up from 0 V to the set value (in this example, 3.3 V). This charge arrives in the form of inrush current. Inrush current can be calculated using the following equation:

Where:

C = output capacitance

dV = output voltage

dt = rise time

The TPS22960 offers selectable rise time control for V_OUT. This feature allows the user to control the inrush current during turnon. Equation 1 can be used to find the required rise time to limit the inrush current to the design requirements

dt = 290 µs (4)

To ensure an inrush current of less than 200 mA, SR must be set high for a rise time greater than 290 µs. The following application curves show the different inrush for each SR setting in this design example.