Figure 3-1 shows the typical soft start sequence of TPS56837. Once the enable signal triggers the EN on threshold, the internal VCC starts to ramp up. After the voltage of internal VCC crosses the UVLO rising threshold, it takes 40-100 us to finish reading and setting of MODE. Once MODE setting is done, the switching frequency and current limit are latched and do not change until VIN or EN toggles to restart device. Then after a delay of around 64 us, the soft-start circuitry works as seen in Section 2.1. Vout ramps up smoothly with a set soft start time. When Vout is up to the reference voltage after T_ss, PGOOD turns to high after a delay.

Figure 3-1 Soft Start Sequence