A motor-driven integrated circuit comprises a plurality of position comparators, a timer and a central processing. Each of the plurality of position comparators receives a pole detection signal denoted a position of a rotor of a motor. The timer receives a timing interrupt signal output by the plurality of position comparators when a predetermined edge of the pole detection signal is generated and records a time of the predetermined edge. The central processing unit obtains a rotation speed of the motor according to a time difference between two predetermined edges.