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stealthChop is an extremely quiet mode of operation for stepper motors. It is based on a
voltage mode PWM. In case of standstill and at low velocities, the motor is absolutely
noiseless. Thus, stealthChop operated stepper motor applications are very suitable for
indoor or home use. The motor operates absolutely free of vibration at low velocities.
With stealthChop, the motor current is applied by driving a certain effective voltage into
the coil, using a voltage mode PWM. With the enhanced stealthChop2, the driver automatically adapts
to the application for best performance. No more configurations are required. Optional configuration
allows for tuning the setting in special cases, or for storing initial values for the automatic adaptation
algorithm. For high velocity drives spreadCycle should be considered in combination with stealthChop.

stealthChop2 integrates an automatic tuning procedure (AT), which adapts the most important
operating parameters to the motor automatically. This way, stealthChop2 allows high motor dynamics
and supports powering down the motor to very low currents. Just two steps have to be respected by
the motion controller for best results: Start with the motor in standstill, but powered with nominal
run current (AT#1). Move the motor at a medium velocity, e.g. as part of a homing procedure (AT#2).
Figure 6.2 shows the tuning procedure.

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For each active edge on STEP, microPlyer produces microsteps at 256x resolution, as shown in Figure
11.2. It interpolates the time in between of two step impulses at the step input based on the last
step interval. This way, from 2 microsteps (128 microstep to 256 microstep interpolation) up to 256
microsteps (full step input to 256 microsteps) are driven for a single step pulse.
The step rate for the interpolated 2 to 256 microsteps is determined by measuring the time interval of
the previous step period and dividing it into up to 256 equal parts. The maximum time between two
microsteps corresponds to 220 (roughly one million system clock cycles), for an even distribution of
256 microsteps. At 12MHz system clock frequency, this results in a minimum step input frequency of
roughly 12Hz for microPlyer operation. A lower step rate causes a standstill event to be detected. At
that frequency, microsteps occur at a rate of (system clock frequency)/216
~ 256Hz. When a stand still is
detected, the driver automatically begins standby current reduction if selected by pin PDN.

Attention
microPlyer only works perfectly with a stable STEP frequency.