LMD18245_06 Datasheet, PDF (13/21 Pages) National Semiconductor (TI) – 3A, 55V DMOS Full-Bridge Motor Driver

The Typical Application
Figure 7 shows the typical application, the power stage of a
chopper drive for bipolar stepper motors. The 20 kΩ resistor
and 2.2 nF capacitor connected between RC and ground set
the off-time at about 48 µs, and the 20 kΩ resistor connected
between CS OUT and ground sets the gain at about 200 mA
per volt of the threshold for chopping. Digital signals control
the thresholds for chopping, the directions of the winding
currents, and, by extension, the drive type (full step, half
step, etc.). A µprocessor or µcontroller usually provides the
digital control signals.
FIGURE 7. Typical Application Circuit for Driving Bipolar Stepper Motors
01187816
ONE-PHASE-ON FULL STEP DRIVE (WAVE DRIVE)
To make the motor take full steps, windings A and B can be
energized in the sequence
A→B→A*→B*→A→ …,
where A represents winding A energized with current in one
direction and A* represents winding A energized with current
in the opposite direction. The motor takes one full step each
time one winding is de-energized and the other is energized.
To make the motor step in the opposite direction, the order of
the above sequence must be reversed. Figure 8 shows the
winding currents and digital control signals for a wave drive
application of the typical application circuit.
TWO-PHASE-ON FULL STEP DRIVE
To make the motor take full steps, windings A and B can also
be energized in the sequence
AB→A*B→A*B*→AB*→AB→ …,
and because both windings are energized at all times, this
sequence produces more torque than that produced with
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