This power management chip is a power switch chip controlled by current-mode PWM, which integrates high-voltage starting circuit and high-voltage power tube, and its packaging and pin arrangement are relatively common.
Pin 1 and pin 2: The chip ground is also the source of the built-in high-voltage MOS transistor.
Pin 3: Feedback input, compared with internal reference voltage.
Pin 4: Chip power supply.
Pin 5, Pin 6, Pin 7, Pin 8: The drain of the built-in high-voltage MOS tube is also used for chip startup.