Dual Full-Bridge PWM Motor Driver with Brake Using A3968


The A3968 bidirectionally controls two DC motors. The device includes two full-bridges capable of continuous output currents of ±650 mA and operating voltages to 30 V. Motor winding current can be controlled by the internal fixed-frequency, pulse-width modulated (PWM), current-control circuitry. The peak load current limit is set by user selection of a reference voltage and current-sensing resistors.The fixed-frequency pulse duration is set by a user-selected external RC timing network. The capacitor in the RC timing network also determines a user-selectable blanking window that prevents false triggering of the PWM current-control circuitry during switching transitions.To reduce on-chip power dissipation, the full-bridge power outputs have been optimized for low saturation voltages. The sink drivers feature the Allegro® patented Satlington® output structure. The Satlington outputs combine the low voltage drop of a saturated transistor and the high peak current capability of a Darlington.For each bridge, the INPUTA and INPUTB terminals determine the load-current polarity by enabling the appropriate source and sink driver pair. When a logic low is applied to both INPUTs of a bridge, the braking function is enabled. In brake mode, both source drivers are turned off and both sink drivers are turned on, thereby dynamically braking the motor. When a logic high is applied to both INPUTs of a bridge, all output drivers are disabled.Special power-up sequencing is not required. Internal circuit protection includes thermal shutdown with hysteresis, ground-clamp and flyback diodes, and crossover-current protection.

  •     ±650 mA continuous output current
  •     30 V output voltage rating
  •     Internal fixed-frequency PWM current control
  •     Satlington® sink drivers
  •     Brake mode
  •     User-selectable blanking window
  •     Internal ground-clamp and flyback diodes
  •     Internal thermal-shutdown circuitry
  •     Crossover-current protection and UVLO protection