SLVS875C January 2009 – November 2014 TPS54332
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’s reference voltage fed into the error amplifier and will regulate the output accordingly. A capacitor (CSS) 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 Vref is 0.8V and the ISS current is 2 μA.
The slow-start time should be set between 1 ms to 10 ms to ensure good start-up behavior. The slow-start capacitor should 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.