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Premier Solution For MicroStepping Performance:
DMOS MicroStepping Driver - 32 MicroStep/Step 
Worcester, MA, August 11, 2000 - Allegro MicroSystems, Inc. announces the release of dual full-bridge microstepping PWM (pulse-width modulation) motor drivers, the A3972 and the A3973. Full-featured products, the A3972 and A3973 are serial-controlled microstepping drivers with DMOS (all N-channel) outputs for decreased power dissipation and higher peak-current capability compared to bipolar drivers.
The A3972SB is based on Allegro's new ABCD3 (Allegro's Bipolar CMOS and DMOS Generation 3) power integrated circuit technology, which combines low voltage CMOS logic, bipolar control circuits and power DMOS transistors on a single chip. With this technology, the A3972SB is capable of output currents up to ±1.5 A and operating voltages to 50 V. The A3973, a pin for pin compatible product is designed for lower voltage applications.
The A3972SB features internal fixed off-time PWM current control timing circuitry that can be programmed via a serial interface to operate in slow, fast, and mixed decay modes and microsteppping resolutions from Full Step to 32 MicroStep/Step. A built-in 4 MHz oscillator is used for digital timing.
Load currents are set via the serial port with two 6-bit linear digital/analog converters in conjunction with a reference voltage. The 6-bit control allows maximum flexibility in torque control for a variety of step methods, from microstepping to full-step drive. Load current is set in 1.56% increments of the maximum value.
Synchronous rectification circuitry allows the load current to flow through the low rDS(on) of the DMOS output driver during the current decay. This feature eliminates the need for external clamp diodes in most applications, saving cost and external component count and minimizing power dissipation. Other features of the A3972SB include a precision 2 V reference, inputs compatible with 3.3 V or 5 V control signals, and "sleep" or "idle" modes. Included in the A3972SB, are thermal shutdown with hysteresis, and crossover-current protection. Special power sequencing is not required. Products are ideally suitable for stepper motor applications within the following markets: office automation, industrial controls, robotics and medical equipment.
Package options include a 24-lead "batwing" DIP package for the A3972.
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