We demonstrate a hybrid photonic integrated laser with intrinsic linewidth of 40 Hz, while offering megahertz actuation bandwidth with the tuning range larger than 1 GHz, attained by a DFB laser self-injection locking to a high-Q Si3N4 microresonator with integrated AIN piezoelectrical actuator, allowing both single line operation and microcomb generation. We develop a compact FMCW LiDAR engine with triangular chirp optical signals at a rate up to 1 MHz, without requiring any linearization, and perform an optical ranging demo.