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

Allegro A4964 block diagram

Called A4964, it works with external n-channel mosfets and is designed to work in systems where a small microcontroller provides communication to a central  electronic control unit (ECU), plus intelligent fault and status handling.

It provides the power supply and watchdog for the microcontroller, as well as 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 (see diagrams).

Sensor-less, brush-less

Allegro A4964 typical appsMotor drive is through three-phase sinusoidal current, where phase commutation is determined, without the need for independent position sensors, by monitoring motor back-EMF.

“The sensor-less start-up scheme includes forward and reverse pre-rotation [windmill] detection and synchronisation, and allows the device to operate over a wide range of motor and load combinations,” said Allegro.

There are three control modes:

  • open loop (voltage) control
  • current (torque limit) control
  • closed-loop speed control

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 indicate: under-voltage, over-temperature, and power bridge faults, and can protect the power switches under “most” short-circuit conditions, said the firm.

It is available in 36pin QFN and 32-lead QFP – both with exposed thermal pad for heat sinking.