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The L9942 microstepping

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The L9942 microstepping

The L9942 stepper motor controller has full step, half step and micro-stepping modes. The

micro-stepping mode provides for 32 programmable current regulated steps over 360°

electrical. That translates to 8 different levels of current per quadrant.

Figure 1. L9942 microstepping mode

Each step current is regulated by PWM control. The PWM on-time is fixed by an oscillator.

The off-time is set by the current measured. An internal current mirror feedback provided

from the high side switches is compared to a preset (programmable) current value through a

look-up table. When the current in the phase matches the value in the look-up table the

phase is turned off until the next PWM on-time. As a result a current sine wave is

approximated in 32 steps through PWM control of the outputs. This also applies to half step

and full step modes of operation as well.