Three-phase brushless DC motor pre-driver IC from Allegro

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 7.5 V 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, Allegro's A4931 synchronous rectification feature will turn on the appropriate MOSFET(s) during current decay to reduce power dissipation.



High side N-channel MOSFETs are used because they are lower in cost than P-Channel MOSFETs of equivalent 'on' resistance. No external components are required to drive the MOSFETS.



Internal circuit protection includes thermal shutdown with hysteresis, undervoltage lockout, and locked-rotor and dead-time protection. For the locked-rotor protection, a programmable lock-time detection feature limits the time at stall before the outputs are disabled to prevent output stage or

motor overheating.



Special power-up sequencing is not required. Operating temperature range is -20°C to +105°C.



The Allegro A4931 is supplied in a 5 x 5 mm 28-lead QFN package with exposed pad. The small footprint is important in applications where PC board space is limited. The exposed pad package has low thermal resistance for improved thermal performance. The package is lead (Pb) free with 100% matt tin

lead-frame plating.



The A4931 is targeted at the office automation, telecommunications, consumer and industrial markets, in applications such as driving drums on laser printers and copiers or fans in telecommunications or consumer equipment.