New Industry Products

Allegro MicroSystems Debuts A3977 Motor Driver IC

September 16, 2001 by Jeff Shepard

Allegro MicroSystems Inc. (Worcester, MA) introduced a new micro-stepping 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.

Allegro's new A3977 is designed to operate bipolar stepper motors in full-, half-, quarter- and eighth-step modes, with output drive capability of 35V and ±2.5A. 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 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 operation. Internal circuit protection includes thermal shutdown with hysteresis, under-voltage lockout and crossover current protection. Special power-up sequencing is not required.

The A3977 has a 16-week lead time to market and is offered in a choice of two power packages, a 44-lead plastic PLCC with a copper batwing tab and a low profile (1.1mm) 28L eTSSOP with exposed power tab. The A3977 will be priced at $3.67 per part for quantities of 1,000.