The TPS563201 and TPS563208 have an internal 1-ms soft-start. When the EN pin becomes high, the internal soft-start function begins ramping up the reference voltage to the PWM comparator.

If the output capacitor is pre-biased at startup, the devices initiate switching and start ramping up only after the internal reference voltage becomes greater than the feedback voltage V_FB. This scheme ensures that the converters ramp up smoothly into regulation point.