Quad DMOS Full-Bridge PWM Motor Driver

The A3988 quad DMOS full-bridge driver from Allegro MicroSystems (Worcester, MA) can drive two stepper motors or four DC motors. Each fullbridge output is rated to 1.2 A and 36 V. The A3988 includes fixed off-time pulse width modulation (PWM) current regulators; DC motors in forward, reverse, and coast modes; and 2-bit nonlinear DACs (digital-toanalog converters) that allow stepper motors to be controlled in full, half, and quarter steps. The PWM current regulator uses Allegro's patented mixed decay mode for reduced audible motor noise, increased step accuracy, and reduced power dissipation.

Internal synchronous rectification control circuitry is provided to allow power dissipation during PWM operation. Protection features include thermal shutdown with hysteresis, undervoltage lockout (UVLO), and crossover current protection. Special powerup sequencing is not required. The A3988 is supplied in either an EV or JP package, with exposed power tabs for enhanced thermal performance. The EV is a 6 × 6-mm, 36-pin QFN package with a nominal overall package height of 0.90 mm. The JP is a 7 × 7-mm, 48-pin LQFP. Both packages are lead-free, with 100% matte tin leadframe plating.

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