A3987: Allegro Expands Their Microstepping Motor Driver Family With A New High-Voltage Device With Over-Current Protection -

Worcester, MA, September 13, 2006 — Allegro announces a new microstepping motor driver with built in translator for easy operation. This new motor driver augments the existing line of motor drivers by offering an output drive capability of 50 V and ±1.5 A. Allegro’s A3987 is designed to operate bipolar stepper motors in full, half, quarter and sixteenth step modes and includes a fixed off time current regulator which has the ability to operate in slow or mixed decay modes. The A3987 is targeted at the office automation and industrial markets.

The translator is the key to the easy implementation of the A3987. By simply inputting one pulse on the step input the motor will take one microstep. There are no phase sequence tables, high frequency control lines or complex interfaces to program. The A3987 interface is an ideal fit for applications where a complex µP is unavailable or over-burdened.

The A3987 chopping control automatically selects the current decay mode (slow or mixed). When a STEP signal occurs, the device 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 to 30.1% fast decay. 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 PWM operation. Internal circuit protection includes thermal shutdown with hysteresis, over current protection, under voltage lockout and crossover current protection. Special power up sequencing is not required.

Allegro’s A3987 is supplied in a low profile (1.1mm) 24L eTSSOP (suffix “LP”) with exposed power tab.

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