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Allegro MicroSystems, Inc. Announces a New DMOS Motor
Driver IC with Translator Integrated on Chip
Microstepping Made Easy 
Worcester, MA - September 10, 2001 - Allegro MicroSystems, Inc. introduces a new microstepping motor driver IC with built in translator for easy operation. By simply inputting one pulse on the step input, the motor will take one microstep. There are no phase sequence tables, high frequency control lines or complex interfaces to program. This new motor driver interface is an ideal fit for applications where a complex microprocessor is unavailable or over-burdened, because the critical microstepping control is up-integrated providing a motor driver IC that can run independently of a microprocessor.
Allegro's new A3977 is designed to operate bipolar stepper motors in full, half, quarter and eighth step modes, with output drive capability of 35 V and ±2.5 A. The A3977 includes a fixed off-time current regulator that has the ability to operate in slow, fast or mixed-decay modes, automatically selected by the chopping control. When a STEP signal occurs, the A3977 determines if that step results in a higher or lower current in each of the motor phases. If the change is a higher current, then the decay mode is set to slow decay. If the change is a lower current, then the decay mode will be set by the voltage at the percent-fast-decay (PFD) input. This current decay control scheme results in reduced audible motor noise, increased step accuracy, and reduced power dissipation. Internal synchronous rectification control circuitry is provided to improve power dissipation during pulse-width modulated (PWM) operation. Internal circuit protection includes thermal shutdown with hysteresis, under-voltage lockout (UVLO) and crossover current protection. Special power up sequencing is not required.
Allegro's microstepping motor driver IC is targeted to meet the needs of the office automation, industrial and medical markets.
About Allegro
Allegro MicroSystems, Inc. is a leader in developing, manufacturing and marketing high-performance power and Hall-effect sensor integrated circuits. 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 - Marketing Communications
Tel: (508) 854-5363
sfennelly@allegromicro.com
Technical Contact:
Bob Brodeur
Strategic Marketing Manager
Tel: (508) 854-5558
bbrodeur@allegromicro.com