7.3.1 Startup

When the device is enabled, the high-side FET turns on to charge the output capacitor linearly by a DC current which is called the pre-charge phase. The pre-charge startup phase terminates until the output voltage being close to the input voltage (typically VOUT = VIN -115mV). Once the output capacitor has been biased close to the input voltage (VOUT = VIN -115mV), the device starts switching which is called the boost soft start phase. During the soft start phase, there is a soft start voltage controlling the FB pin voltage, and the output voltage rising slope follows the soft start voltage slew rate (typically). The soft start phase completes when the soft start voltage reaches the internal reference voltage. The device begins to operate normally and regulates the output voltage at the pre-set target value.