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23 Qorvo 2021 Manufacturers construct brushless DC motors using fixed permanent magnets on the rotor drive shaft and a series of field windings (typically three) inside the motor casing. Switching the current through the three field windings in sequence results in the rotation of the drive shaft. Controlling the pulse width and the switching frequency of the drive to each field coil provides control of motor speed, acceleration, and output torque. A closed-loop feedback of the rotor's operation to the three-phase motor control algorithm is required to closely monitor and control the current state of the drive shaft's rotation. The two most popular methods of providing this feedback are: Affixing an encoder disk or other form of rotational sensor to the rotor shaft. Sensing the back electromagnetic field induced by the rotor's permanent magnets within the field windings. Field-oriented control (FOC) refers to using the induced field voltage. A sensorless method helps improve overall motor reliability and reduces the bill of materials (BOM) cost. The Architecture of a BLDC Motor Controller As mentioned, three distinct circuit functions are required for a brushless motor controller. These three distinct circuit functions are achieved through: A microcontroller that runs the motor control algorithm Pulse Width Modulation (PWM) circuitry that provides the switching signals A power output stage that drives the motor An analog-to-digital function converts the shaft rotational sensor signals into the digital domain for processing by the microcontroller. When designing an embedded motor controller, several designs can be a consideration. The initial factors that help shape the overall design of an embedded motor controller are: The power/torque required The power supply source The shaft speed Today's fast-paced prototype-to-production focus tends to dissuade design engineers from developing a custom controller using discrete parts. The more popular design route is to use an off-the-shelf microcontroller to run the control algorithm. Most microcontrollers incorporate a wide range of ADC/DAC conversion functions in addition to different peripheral interface options, clocks, and timers. A suitably equipped microcontroller might provide most of the required circuit functions. Still, many microcontrollers tend not to be optimized for motor control applications or incorporate the necessary half/full H bridge motor drive functions. Also, energy management is an essential function of most applications today and is especially important in motor control applications where the energy efficiency rating is usually a key selection criterion for customers. Power management ICs are available, but this requires the engineering team to integrate another IC into the design, increasing the BOM cost and board space requirements. As more consumer and industrial motor-based appliances adopted a brushless DC motor design, the need for a device that includes all of the necessary functions drove Qorvo to develop a full-featured power application controller (PAC ™ ). Qorvo's PAC5556 Power Application Controller ® (PAC ™ ) integrates all the required analog, power management, and gate drive signal sources within a single, compact package. Brushless DC (BLDC) motors have become the default choice of motor for a wide range of battery and line-powered equipment and appliances.