Automotive-grade 3-phase motor-control ICs with built-in commutation logic

The on-chip commutation logic consists of a decoder and state machine which together read the inputs of three Hall sensor inputs (or I/O signals from a microprocessor). The IC then outputs the correct gate drive signals to control six (three high-side, three low-side) external N-channel MOSFETs for driving the 3-phase motor.

The highly flexible input logic provides a wide range of control possibilities including coast, brake and pulse-width modulation functions and the facility for single-pin bi-directional control of the motor. Output pins provide status and diagnostic information on speed and direction and provide signals to enable closed-loop speed control.

Other key features incorporated on the IC are a 5 V supply for Hall sensors (used in conjunction with an external NPN transistor) and an integrated charge pump which allows operation at 100% PWM duty cycle. The driver ICs operate over a wide battery voltage range (5.5 V to 50 V) and feature extensive diagnostics and a low-current quiescent mode.

The two devices are identical apart from the addition of an optional pre-positioning function on the A3931. This operates by driving the three Hall inputs low to provide a known start-up position for the motor by forcing a position between two detent positions. This start-up condition aids any algorithms that may be used with the IC (such as sensorless back EMF commutation schemes).

The A3930 and A3931 will operate over a temperature range from -40ºC to +150ºC) and voltages from 5.5 V to 45 V, making them suitable for use in 14 V or 24 V automotive ‘under hood’ applications.

Both the A3930 and A3931 are offered in a small thermally efficient 48L eLQFP package.