8.3.7 Soft Start

The integrated soft-start circuit prevents input inrush current impacting the TPS560430 and the input power supply. Soft-start is achieved by slowly ramping up the target regulation voltage when the device is first enabled or powered up. The typical soft-start time is 1.8 ms.

The TPS560430 also employs over-current protection blanking time T_{OCP_BLK} (33 ms typical) at the beginning of power-up. Without this feature, in applications with a large amount of output capacitors and high V_OUT, the inrush current is large enough to trigger the current-limit protection, which may make the device entering into hiccup mode. The device tries to restart after the hiccup period, then hit current-limit and enter into hiccup mode again, so V_OUT cannot ramp up to the setting voltage ever. By introducing OCP blanking feature, the hiccup protection function is disabled during T_{OCP_BLK}, and TPS560430 charges the V_OUT with its maximum limited current, which maximizes the output current capacity during this period. Kindly note that, the peak current limit (I_{HS_LIMIT}) and valley current limit (I_{LS_LIMIT}) protection function are still available during T_{OCP_BLK}, so there is no concern of inductor current running away.