Allegro: sensorless sinusoidal three-phase gate controller
Allegro MicroSystems Europe has introduced the release of a three-phase, sensorless, brushless DC motor controller for use with external N-channel power MOSFETs. Allegro’s A4964 is specifically designed for the automotive market with target applications to include engine cooling fans and oil and water pumps. It is designed to provide the motor control functions in a system where a small microcontroller provides the communication interface to a central ECU and intelligent fault and status handling. The A4964 provides the supply and watchdog for the microcontroller and the high-voltage interfaces between the microcontroller and the central ECU and ignition switch. It can also operate as an independent single chip remote motor controller.
The motor is driven using a three-phase sinusoidal current drive where phase commutation is determined, without the need for independent position sensors, by monitoring the motor back-EMF (bemf). The sensorless start-up scheme includes forward and reverse pre-rotation (windmill) detection and synchronization, and allows the device to operate over a wide range of motor and load combinations.
The A4964 offers three control modes, open loop (voltage) control, current (torque limit) control, and closed-loop speed control which allows it to be used in a wide range of applications. Control mode, operating mode, and bridge parameters are programmed through an SPI-compatible serial interface. A single current sense amplifier provides peak current limiting and average current measurement through the serial interface. Integrated diagnostics provide indication of under-voltage, over-temperature, and power bridge faults and can protect the power switches under most short-circuit conditions. The A4964 is provided in both a 36-terminal QFN and a 32-lead QFP package, both with exposed thermal pad for enhanced power dissipation.