What is a soft-start function?

DC/DC Switching RegulatorsSwitch ICsFunction

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 Power management IC (LDO regulator or DCDC converter) will cause a large inrush current and overshoots of output voltage.

The Power management IC 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

  

  (Graphical view)

• With Soft-Start Function

  

  (Graphical view)