This AT9933 is a PWM controller IC, designed to control an LED lamp driver using a low-noise boost-buck. It produces a low-frequency PWM dimming input that can accept an external control signal with a duty cycle of 0 – 100% and a high dimming ratio, according to the datasheet.
Therefore, the AT9933 LED driver IC is typically ideal for automotive LED lamps since this IC has features such as Constant current LED Driver, Ambient temperature rating
up to 125°C, Meets AEC-Q100 requirements, Input and output current
sensing, Enable & PWM dimming, Internal 75V linear regulator, Steps
input voltage up or down and low EMI.
And the figure above shows the AT9933 typical application circuit (click to enlarge). In the AT9933 datasheet
you will find Pin Configuration, Product Marking, functional
description (Input Voltage Regulator, PWM Dimming, Current Comparators,
Over-voltage Protection, Damping Circuit and etc).