Allegro MicroSystems, LLC Announces New DMOS Microstepping Driver with Translator and Overcurrent Protection

Proprietary Current Control Method Maximizes Microstepping Accuracy

Allegro MicroSystems, LLC announces a new integrated bipolar stepper motor driver IC with built-in translator for easy operation. Allegro’s A5985 is designed to operate bipolar stepper motors from full-step up to 1/32 step modes that are selectable by MSx logic inputs. This new device has an output drive capacity of up to 40 V and ±2 A and operates with a single supply. It is targeted at the office and industrial automation markets with key applications to include: automatic teller machines, point of sale and laser printers, 3D printers, copiers, CCTV cameras, sewing machines, vending, and robotics.

Allegro’s A5985 motor driver IC introduces a proprietary Adaptive Percent Fast Decay (APFD) algorithm to optimize the current waveform over a wide range of stepper speeds and stepper motor characteristics. APFD adjusts, on-the-fly, the amount of fast decay with the goal of maintaining current regulation while minimizing current ripple. This adaptive feature improves performance of the system resulting in reduced audible motor noise, reduced vibration, and increased step accuracy. The translator is the key to the easy implementation of the A5985. Simply inputting one pulse on the STEP input drives the motor one microstep. There are no phase sequence tables, high frequency control lines, or complex interfaces to program. The A5985 interface is an ideal fit for applications where a complex microprocessor is unavailable or is overburdened. 

Internal synchronous rectification control circuitry is provided to improve power dissipation during PWM operation. Internal circuit protection included: Overcurrent protection for motor lead short to ground or supply, thermal shutdown with hysteresis, undervoltage lockout (UVLO), and crossover-current protection. Special power-on sequencing is not required.

The A5985 is supplied in a 28-pin, 5 mm × 5 mm × 0.90 mm QFN package (ET designator) with exposed pad for enhanced thermal dissipation, The package is lead (Pb) free (suffix –T), with 100% matte tin plated leadframe.