3955

3955 FULL-BRIDGE PWM MICROSTEPPING MOTOR DRIVER PFD REF RC GROUND GROUND LOGIC SUPPLY PHASE D2 1 2 3 4 LOGIC 5 6 7 8 VCC 12 11 10 9 GROUND SENSE OUTA D1 VBB 16 15 14 13 LOAD SUPPLY OUTB D0 GROUND Data Sheet 29319.41 The A3955SB and A3955SLB are designed for driving one winding of a bipolar stepper motor in a microstepping mode. The outputs are rated for continuous output currents to ±1.5 A and operating voltages to 50 V. Internal pulse-width modulated (PWM) current control combined with an internal three-bit nonlinear digital-to-analog converter allows the motor current to be controlled in full-, half-, quarter-, or eighth-step (microstepping) modes. Nonlinear increments minimize the number of control lines necessary for microstepping. Microstepping provides for increased step resolution, and reduces torque variations and resonance problems at low speed. Internal circuitry determines whether the PWM current-control circuitry operates in a slow (recirculating) current-decay mode, fast (regenerative) current-decay mode, or in a mixed current-decay mode in which the off time is divided into a period of fast current decay with the remainder of the fixed off time spent in slow current decay. The combination of user-selectable current-sensing resistor and reference voltage, digitally selected output current ratio; and slow, fast, or mixed current-decay modes provides users with a broad, variable range of motor control. Internal circuit protection includes thermal shutdown with hy...