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High-Performance Power ICs and Hall-Effect Sensors
Allegro Introduces a New Three-Phase Brushless DC
Motor Pre-Driver
Designed for Lower Current Applications 
Worcester, MA, September 28, 2007 — Allegro MicroSystems, Inc. introduces a new three-phase brushless DC motor pre-driver targeted at the office automation, telecommunications, consumer and industrial markets. It is designed with outputs for a direct high current gate drive of an all N-channel power MOSFET three phase bridge with a maximum supply voltage of 38 V. It also includes, 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. ENABLE, DIRECTION and BRAKE inputs can be used to control the motor, speed, position and torque. Output speed can be regulated using FG1 (once per each Hall transition) and FG2 (once per Hall A transition) outputs.
The external MOSFETS can be PWM’d with 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.
The A4931 uses cost efficient Hall elements with noise filtering to prevent false commutation signals. A 7.5 V regulated supply output is provided to power the three HALL elements. Internal circuit protection includes thermal shutdown with hysteresis, under voltage lockout, locked rotor and dead time protection. Special power up sequencing is not required. Operating temperature range is β20°C to 105°C.
Allegro’s A4931 is supplied in a 5×5 mm 28 lead QFN package with exposed thermal pad. This small footprint package is lead (Pb) free with 100% matte tin leadframe plating.
About Allegro
Allegro MicroSystems, Inc. is a leader in developing, manufacturing and marketing high-performance power integrated circuits and integrated Hall-effect magnetic sensors. Allegro’s innovative solutions serve high-growth applications within the automotive, communications, computer/office automation, consumer and industrial markets. Allegro is headquartered in Worcester, Massachusetts (USA) with design and applications centers located in North and South America, Asia, and Europe. Further information about Allegro can be found at www.allegromicro.com.
Editorial Contact:
Stephanie Fennelly
Director β Marketing Communications
Tel: (508) 854-5363
sfennelly@allegromicro.com