Microstepping motor drive ICs with simple command interfacing

February 03, 2016 // By Graham Prophet
Allegro’s A5976, A5977 and A5979 have been designed to operate bipolar stepper motors in full-, half-, quarter-, eight, (A5977) and sixteenth- (A5976/79) step modes; the ICs are complete microstepping motor driver ICs with built-in translators.

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 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 program. The interface is a good 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 (overcurrent protection) thermal shutdown with hysteresis, undervoltage lockout (UVLO), 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, under 1.2-mm profile, 28-pin TSSOP with exposed thermal pad. Data sheets are at; A5976, A5977 and A5979

Allegro MicroSystems, www.allegromicro.com