The Motor Control IC TDA5140AT has been especially designed for driving brushless VCR scanning motors.
Besides the back-EMF sensing, the commutation timing and the drive of the motor coils the IC features also a position indication method of the scanner drum with respect to the motor coils and some speed control circuitry.
For position indication the PG-IN input and the PG/FG output are used.
For the speed control the IC has an operational amplifier that drives an external series voltage regulator.
In this paper the functioning of both the position indication and the speed control have been described.
1. Circuit description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Timing PG-IN and PG\FG signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Speed control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7