DMOS Microstepping Driver Has Translator, Overcurrent Protection

14 July 2016

Allegro MicroSystems, LLC has announced an integrated bipolar stepper motor driver IC with built-in translator for easy operation. Allegro’s A5985is designed to operate bipolar stepper motors from full-step up to 1/32 step modes that are selectable by MSx logic inputs. This device has an output drive capacity of up to 40 V and ± 2 A and operates with a single supply.

Allegro A5985 integrated bipolar stepper motor driver IC. Source: Allegro Microsystems Allegro A5985 integrated bipolar stepper motor driver IC. Source: Allegro Microsystems

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 suits applications where a complex microprocessor is unavailable or overburdened.

Internal synchronous rectification control circuitry is provided to improve power dissipation during PWM operation. Internal circuit protection includes: overcurrent protection for motor lead short to ground or supply, thermal shutdown with hysteresis, undervoltage lockout 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-free with a 100% matte tin-plated leadframe.

The A5985GET-T is priced at $1.33 in quantities of 1,000.

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