SLVSHC9 January 2024 TPS56A37
PRODUCTION DATA
The TPS56A37 has an adjustable soft-start time that can be set by connecting a capacitor between SS and AGND. Leaving the SS pin floating is set to default internal soft start time 1.8ms. When the EN pin becomes high, the soft-start charge current (ISS) begins charging the external capacitor (CSS) connected between SS and AGND. The device tracks the lower of the internal soft-start voltage or the external soft-start voltage as the reference. The equation for the soft-start time (TSS) is shown in Equation 2.
If the external capacitor (CSS) has pre-stored voltage at start-up, the device initially discharge the external capacitor voltage to lower voltage then charge again to prevent inrush start-up.
If the output capacitor is prebiased at start-up, the device initiates switching and starts ramping up only after the internal reference voltage becomes greater than the feedback voltage VFB. This scheme makes sure that the converters ramp up smoothly into regulation point.