Automotive sensor-less, brush-less controller for 3Φ DC motors

Allegro has introduced a three-phase, sensorless, brushless DC motor controller that can be used with cars with engine cooling fans, oil pumps and water pumps. A4964, which works with external n-channel mosfet, and is designed to work in systems where small microcontrollers provide communication with a central electronic control unit (ECU) and intelligent fault and status processing. It provides power and watchdog for the microcontroller, as well as a high voltage interface between the microcontroller and the central ECU and ignition switch. It can also operate as a stand-alone, single-chip remote motor controller (see diagram). Allegro A4964 typical application Motor drive is performed by three-phase sinusoidal current. By monitoring the back-EMF of the motor, the phase commutation can be determined without a separate position sensor. There are three control modes: Open-loop (voltage) control Current (torque limit) control Closed-loop speed control The control mode, operation mode and bridge parameters are programmed via an SPI-compatible serial interface. A single current-sense amplifier provides peak current limit and average current measurement through a serial interface. The company said comprehensive diagnostics showed undervoltage, overheating, and bridge failure, and could protect power switches in "most" short-circuit conditions. It is available in 36-pin QFN and 32-pin QFP models, both with exposed thermal pads for heat dissipation.