3957

3957 FULL-BRIDGE PWM MICROSTEPPING MOTOR DRIVER A3957SLB NO CONNECT PFD REF NO CONNECT RC GROUND GROUND D3 LOGIC SUPPLY PHASE D2 NO CONNECT 1 2 3 4 5 6 7 8 9 10 11 12 NC VCC NC NC NC VBB NC 24 23 22 21 20 19 18 17 NC 16 15 NC 14 13 NO CONNECT LOAD SUPPLY OUTB NO CONNECT D0 GROUND GROUND SENSE NO CONNECT OUTA NO CONNECT D1 Data Sheet 29319.44† The A3957SA and A3957SLB 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 four-bit nonlinear digital-to-analog converter allows the motor current to be controlled in full-, half-, quarter-, eighth-, or sixteenth-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 cur...