ZHCSI17B December 2008 – May 2018 TPS650250
PRODUCTION DATA.
Each of the three converters has an internal soft start circuit that limits the inrush current during start-up. The soft start is realized by using a very low current to initially charge the internal compensation capacitor. The soft start time is typically 750 μs if the output voltage ramps from 5% to 95% of the final target value. If the output is already pre-charged to some voltage when the converter is enabled, then this time is reduced proportionally. There is a short delay of typically 170μs between the converter being enabled and switching activity actually starting. This is to allow the converter to bias itself properly, to recognize if the output is pre-charged, and if so, to prevent discharging of the output while the internal soft start ramp catches up with the output voltage.