Abstract: In a disk drive system, whether the rotation rate of a motor provided to drive a disk is within a rated rotation rate range or not is checked every time the motor makes one complete turn. When the rotation rate of the motor is found to be within the rated range a predetermined number of times consecutively, a status signal, which is used to indicate that the rotation rate of the disk is within the rated range, is brought into a state for indicating that the rotation rate of the disk is within the rated range. This not only prevents the status signal from oscillating at a high frequency, but also allows the status signal to be brought into the state for indicating that the rotation rate of the disk is within the rated range only after the rotation rate of the motor has settled within the rated range. Thus, it is possible to eliminate the possibility of malfunctioning of a disk drive apparatus due to the status signal.

Abstract: A motor driver has a braking control circuit. The braking control circuit shuts off the supply of an electric current to the coils included in the motor when a motor control signal shifts to a predetermined level and, after a predetermined length of time secured in accordance with an index signal, starts application of braking to the rotation of the motor by the use of a braking circuit. The index signal is obtained from the signal that indicates the rotational position of the motor. The motor control signal is fed from a control signal generating circuit to the braking control circuit.