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L99ASC03 Fully-Integrated Motor Driver IC for Three-Phase Brushless Motors Slide 21

Built in Back-EMF detection is optimized for six-step drive mode. There is no need for additional external sensors or components for this function. Pre-commutation allows for very fine control of the motor in a dynamic control scenario where the commutation has to be setup before it actually happens. This can be done up to 45 degrees. Back-EMF detection can be done both during PWM on and off from 0% all the way up to 100% duty cycle. Additionally, the motor does not have to be powered for the function to operate, and a feature in the algorithm allows the device to determine the position of the rotor at any given time. The microcontroller resources required for Back-EMF detection are limited to one general purpose IO pin, a significant advantage.

PTM Published on: 2015-04-06