Allegro Bipolar Stepper Motor Driver A3982

DMOS Stepper Motor Driver with Translator


Top Features

  • Low RDS(ON) outputs
  • Automatic current decay mode detection/selection
  • Mixed and Slow current decay modes
  • Synchronous rectification for low power dissipation
  • Internal UVLO and thermal shutdown circuitry
  • Crossover-current protection


The A3982 is a complete stepper motor driver with builtin translator for easy operation. It is designed to operate bipolar stepper motors in full- and half-step modes, with an output drive capacity of up to 35 V and ±2 A. The A3982 includes a fixed off-time current regulator which has the ability to operate in slow or mixed decay modes.

The translator is the key to the easy implementation of the A3982. Simply inputting one pulse on the STEP input drives the motor one step. There are no phase sequence tables, high frequency control lines, or complex interfaces to program. The A3982 interface is an ideal fit for applications where a complex microprocessor is unavailable or is overburdened.

The chopping control in the A3982 automatically selects the current decay mode (Slow or Mixed). When a signal occurs at the STEP input pin, the A3982 determines if that step results in a higher or lower current in each of the motor phases. If the change is to a higher current, then the decay mode is set to Slow decay. If the change is to a lower current, then the current decay is set to Mixed (set initially to a fast decay for a period amounting to 31.25% of the fixed off-time, then to a slow decay for the remainder of the off-time). 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, undervoltage lockout (UVLO), and crossover-current protection. Special power-on sequencing is not required.

The A3982 is supplied in a 24-pin wide-body SOIC (package LB) with internally-fused power ground leads for enhanced thermal dissipation. It is lead (Pb) free, with 100% matte tin plated leadframe.


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