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 hysteresis,
transient-suppression diodes, and crossover current protection.
Special power-up sequencing is not required.
The A3955S— is supplied in a choice of two power packages; a
16-pin dual-in-line plastic package with copper heat-sink tabs (suffix
‘B’), and a 16-lead plastic SOIC with copper heat-sink tabs (suffix ‘LB’).
For both package styles, the power tab is at ground potential and
needs no electrical isolation.
FEATURES
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