AH291 is a monolithic fan motor controller with Hall sensor’s capability. It contains two complementary open-collector drivers for motor’s coil driving, automatic lock shutdown and restart function relatively. Rotor-lock shutdown detection circuit turns off the output driver when the rotor is blocked to avoid coil overheat. Then, the automatic recovery circuit will restart the motor. These protected actions are repeated and periodic during the blocked period. Until the blocking is removed, the motor recovers and runs normally.