TI highly recommends programing the slow-start time externally because no slow-start time is implemented internally. The TPS54332 effectively uses the lower voltage of the internal voltage reference or the SS pin voltage as the power supply reference voltage fed into the error amplifier and regulates the output accordingly. A capacitor (C_SS) on the SS pin-to-ground implements a slow-start time. The TPS54332 has an internal pullup current source of 2 μA that charges the external slow-start capacitor. The equation for the slow-start time (10% to 90%) is shown in Equation 3. The V_ref is 0.8 V and the I_SS current is 2 μA.

The slow-start time must be set between 1 ms to 10 ms to make sure of good start-up behavior. The slow-start capacitor must be no more than 27 nF.

If during normal operation, the input voltage drops below the VIN UVLO threshold, or the EN pin is pulled below 1.25 V, or a thermal shutdown event occurs, the TPS54332 stops switching.