Allegro MicroSystems has a 3-phase brushless DC motor pre-driver with outputs for the direct high-current gate drive of an all N-channel power MOSFET 3-phase bridge with a maximum supply voltage of 38 V.

The device includes three Hall-element inputs, a sequencer for commutation control, fixed off-time pulse width modulation (PWM) current control and locked rotor protection. Output current is scalable with the choice of external Mosfets.

The Hall element inputs used in the A4931 are lower in cost than the Hall switches normally used, and have internal noise filtering to prevent false commutation signals. A 7.5V regulated supply output is provided to power the three Hall elements.

'Enable', 'direction' and 'brake' inputs can be used to control the motor, speed, position and torque. Output speed can be regulated using the two speed-control outputs, using either one Hall-element or all three Hall transition outputs to provide flexibility for a variety of speed control applications.

The external Mosfets can be PWM-controlled via the 'enable' input or with the internal PWM current regulator.

In both cases, synchronous rectification feature will turn on the appropriate Mosfets during current decay to reduce power dissipation.