SNVS615K January 2010 – February 2018 LM27402
PRODUCTION DATA.
When the EN pin exceeds 1.17 V and both VIN and VDD exceed their UVLO thresholds, the LM27402 begins charging the output linearly to the voltage level dictated by the feedback resistor network. The soft-start time is set by connecting a capacitor from SS/TRACK to GND. After EN exceeds 1.17 V, an internal 3-µA current source begins to linearly charge the soft-start capacitor. Soft-start allows the user to limit inrush currents related to high output capacitance and output slew rate. If a soft-start capacitor is not used, the LM27402 defaults to a digitally-controlled star-tup time of 1.28 ms. The SS/TRACK pin can also be used to ratiometrically or coincidentally track an external voltage source. See the Setting the Soft-Start Time and Tracking sections for more information.