Most microstepping motor drivers require control lines for DACs to set the reference for the PWM current regulator and phase inputs for current polarity control. In more sophisticated drivers, inputs are required for the PWM current control mode to operate in slow, fast, or mixed decay. These control lines can quickly add up to 8 to 12 inputs, depending on the DAC resolution and the necessity of a supply from a system microprocessor. The requirement of these control inputs and complex sequencing tables in the microprocessor add to the system's cost and complexity. A new microstepping motor driver IC, the A3977, solves this problem with its simple 2-Tine Step and Direction interface and an efficient DM05 output (see Fig. 1). For each transition in the Step input, the driver sequences one microstep. This is ideal for unavailable or overburdened microprocessor-controller applications.
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