Simple interface makes microstepping easy & accurate

6th May 2016

Nat Bowers

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Allegro MicroSystems Europe has introduced a family of complete microstepping motor driver ICs with built-in translators. The A5976, A5977 and A5979 have been designed to operate bipolar stepper motors in full-, half-, quarter-, eight, (A5977) and sixteenth- (A5976/79) step modes. All have the output drive capability of 40V and ±2.8A and include a fixed off-time current regulator that has the ability to operate in slow, fast or mixed-decay modes.

This current-decay control scheme results in reduced audible motor noise, increased step accuracy and reduced power dissipation.

The devices are targeted at the office automation and industrial automation markets including textile and sewing machines, vending machines, printers, scanners, copiers, CCTV camera positioning, ATM machines, 3D printing systems and food industry applications.

The translator is the key to the easy implementation of these devices. Simply inputting one pulse on the STEP input drives the motor one step or microstep (two logic inputs determine if it is a full-, half-, quarter-, eighth- or sixteenth-step resolution). There are no phase sequence tables, high-frequency control lines, or complex interfaces to programme. The interface is an ideal fit for 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 OCP thermal shutdown with hysteresis, undervoltage lockout and crossover-current protection. An open-drain FAULT output is included in the A5976 for improved diagnostic reporting. Special power-up sequencing is not required.

All three devices are supplied in a thin (less than 1.2mm) 28-pin TSSOP with an exposed thermal pad (suffix LP) for enhanced thermal dissipation. The package is lead-free (suffix -T), with 100% matt-tin leadframe plating. Operating ambient temperature range is -40 to 105°C.