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High-Performance Power ICs and Hall-Effect Sensors
Allegro MicroSystems, Inc. Announces a New Low Cost
Microstepping Motor Driver IC With Translator
Microstepping Made Easy 
Worcester, MA, November 12, 2002 — Allegro MicroSystems, Inc. introduces a new low-cost microstepping motor driver IC that uses the Allegro translator for microstepping (one-eighth step) operation. The A3967 complements the Allegro stepper motor product line by adding to the family a lower cost IC targeted at bipolar stepper motors that run up to 750 mA. The interface reduces the number of control lines from as many as eight lines down to two (STEP and DIRECTION)!
| Part Number | Output Voltage Rating | Output Current Rating |
|---|---|---|
| A3967 | 30 V | 750 mA |
| A3977 | 35 V | 2.5 A |
By simply inputting one pulse on the STEP input of the A3967, the motor will take one microstep. There are no phase sequence tables, high frequency control lines, or complex interfaces to program. The interface is an ideal fit for applications where a complex microprocessor is unavailable or over-burdened. The critical microstepping control is up-integrated into the driver IC providing a motor driver that can run independently of a microprocessor.
Allegro's new A3967 is designed to operate bipolar stepper motors in full, half, quarter and eighth step modes, with output drive capability of 30 V and ±750 mA. When a STEP signal occurs, the A3967 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 circuit protection includes thermal shutdown with hysteresis, under-voltage lockout (UVLO) and crossover current protection. Special power up sequencing is not required.
With the A3967, low output-saturation voltages are achieved with patented SatlingtonTM sink drivers. The SatlingtonTM output structure combines the low voltage drop of a saturated transistor with the high current capability of a Darlington driver. Also included is 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.
Allegro's microstepping motor driver IC is targeted to meet the needs of the office automation, industrial and medical markets. The A3967 is offered in a 24-lead plastic SOIC with a copper batwing tab.
Allegro MicroSystems, Inc. is a leading supplier of advanced mixed-signal power semiconductors and Hall-effect sensors targeted toward the computer/office, automotive, industrial, telecommunication and consumer markets. With over 2,400 employees, Allegro is headquartered in Worcester, MA and operates multiple wafer-fabrication plants worldwide. Further information on 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