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High-Performance Power ICs and Hall-Effect Sensors
Allegro Announces New Dual Full-Bridge Pwm Motor
Driver
Ideal for Portable Applications or Applications with Limited Board
Space 
Worcester, MA, October 31, 2006 — Allegro MicroSystems, Inc. announces a new dual full-bridge pulse-width modulated (PWM) motor driver designed to drive both windings of a two-phase bipolar stepper motor. The device includes two H-bridges capable of continuous output currents of ±650 mA and operating voltages to 30 V. Motor winding current can be controlled by the internal fixed-frequency, pulse-width modulated (PWM), current-control circuitry. The peak load current limit is set by the user’s selection of a reference voltage and current-sensing resistors.
The fixed-frequency pulse duration is set by a user-selected external RC timing network. The capacitor in the RC timing network also determines a user selectable blanking window that prevents false triggering of the PWM current control circuitry during switching transitions.
To reduce on-chip power dissipation, the H-bridge power outputs have been optimized for low saturation voltages. The sink drivers feature Allegro’s patented Satlington™ output structure. The Satlington™ outputs combine the low voltage drop of a saturated transistor and the high peak current capability of a Darlington.
For each bridge, a PHASE input controls load-current polarity by selecting the appropriate source and sink driver pair. For each bridge, an ENABLE input, when held high, disables the output drivers. Special power-up sequencing is not required. Internal circuit protection includes thermal shutdown with hysteresis, ground-clamp and flyback diodes, and crossover-current protection.
Allegro’s A3969 is supplied in a 28-pin quad MLP/QFN lead (Pb) free plastic package with exposed thermal pad and 100% matte tin leadframe plating. It has a 5 x 5 mm footprint and 0.90 mm nominal height.
About Allegro
Allegro MicroSystems, Inc. is a global leader in the development, manufacture and marketing of high-performance power integrated circuits and integrated Hall-effect magnetic sensors. Allegro’s innovative, system-level solutions serve high-growth applications within the automotive, computer/office automation, industrial, consumer and communications markets, while our leading-edge product and processes reinforce our expertise in motor driver and power management technology. In addition, we also hold leading positions within printer, scanner, copier and portable device (e.g. cellular phones) applications. With more than 2,400 employees, Allegro is headquartered in Worcester, MA. Further information about Allegro can be found at www.allegromicro.com.
About Allegro
Allegro MicroSystems, Inc. is a global leader in the development, manufacture and marketing of high-performance power integrated circuits and integrated Hall-effect magnetic sensors. Allegro’s innovative, system-level solutions serve high-growth applications within the automotive, computer/office automation, industrial, consumer and communications markets, while our leading-edge product and processes reinforce our expertise in motor driver and power management technology. In addition, we also hold leading positions within printer, scanner, copier and portable device (e.g. cellular phones) applications. With more than 2,400 employees, Allegro is headquartered in Worcester, MA. Further information about Allegro can be found at www.allegromicro.com.
Editorial Contact:
Stephanie Fennelly
Director – Marketing Communications
Tel: (508) 854-5363
sfennelly@allegromicro.com