9.2.2.2 Managing Inrush Current

When the switch is enabled, the output capacitors must be charged up from 0 V to V_IN. This charge arrives in the form of inrush current. Given a load capacitance (C_L) of 33 μF, an input voltage (V_IN) of 3.6V and a maximum inrush (I_INRUSH) of 630 mA, use Equation 12 and Equation 13 to solve for Slew Rate (SR).

Equation 12.

Equation 13.

Now that the desired slew rate has been calculated, use SR and V_IN in in Equation 14 to calculate a CT capacitance value.

Equation 14.

A capacitance value of 1007pF is a non-standard value therefore a 1000 pF CT capacitance is used moving forward.

The calculated CT value can be used with Equation 2 and Equation 4 to determine t_ON and t_PG,ON, respectively as shown in Equation 15 and Equation 16.

Equation 15.

Equation 16.