LMD18245_06 Datasheet, PDF (16/21 Pages) National Semiconductor (TI) – 3A, 55V DMOS Full-Bridge Motor Driver

The Typical Application (Continued)
HALF STEP DRIVE WITHOUT TORQUE
COMPENSATION
To make the motor take half steps, windings A and B can be
energized in the sequence
A→AB→B→A*B→A*→
A*B*→B*→AB*→A→ …
The motor takes one half step each time the number of
energized windings changes. It is important to note that
although half stepping doubles the step resolution, changing
the number of energized windings from two to one de-
creases (one to two increases) torque by about 40%, result-
ing in significant torque ripple and possibly noisy operation.
Figure 11 shows the winding currents and digital control
signals for this half step application of the typical application
circuit.
Top Trace: Phase A Winding Current at 1A/div
Bottom Trace: Phase B Winding Current at 1A/div
Horizontal: 1 ms/div
*500 steps/second
01187822
BRAKE A = BRAKE B = 0
01187843
FIGURE 11. Winding Currents and Digital Control Signals for Half Step Drive without Torque Compensation
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