DC/DC Converter Application Note

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 DC/DC converter will cause a large inrush current and overshoots of output voltage. The DC/DC 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).