Application Note : DCDC Converters (Switching Regulators)
The Soft-start function is initiated when the input voltage (VIN) reaches the minimum operating voltage and UVLO voltage after power on, it is to prevent that the DCDC converter will cause a large inrush current and overshoots of output voltage.
The DCDC converter is made to start up in a smooth manner by provision of a start up time (soft-start time).
There are products with an internally fixed soft start time and products with externally adjustable soft-start time setting pin, and products externally adjustable with an oscillator maximum duty cycle (to be explained later).
Without Soft-Start Function
With Soft-Start Function