When the switch is enabled, the output capacitance must be charged up from 0 V to the set value (5 V in this example). This charge arrives in the form of inrush current. Inrush current can be calculated using the equation below.

Where:

• C_L is the output capacitance.
• dVOUT is the change in VOUT during the ramp up of the output voltage when device is enabled.
• dt is the rise time in VOUT during the ramp up of the output voltage when the device is enabled.

The TPS22992 offers an adjustable rise time for VOUT, allowing the user to control the inrush current during turn-on. The appropriate rise time can be calculated using the design requirements and the inrush current equation as shown below.

To ensure an inrush current of less than 200 mA, a C_T value that yields a rise time of more than 1175 µs must be chosen. See the oscilloscope captures in the Application Performance Plots section for an example of how the C_T capacitor can be used to reduce inrush current.