User Manual

AND8399/D
http://onsemi.com
15
Figure 17. Too High Speed Results in Incorrect BEMF Sampling
If the maximum operating speed is lower than the required
operating speed, some of the application parameters need to
be changed to increase the maximum operating speed. Next
are some possible adjustments that could be done.
− Choose stepper motor with lower series resistance
− Choose stepper motor with lower inductance. Keep
in mind that this will have an effect on the torque!
− Increase the operating voltage
− Choose a lower coil current. Keep in mind that this
will result in a lower torque.
− Choose a lower stepping mode (1/4 instead of 1/8
for instance). This will result in longer coil current
zero crossings.
A trick to increase the maximum operating speed without
the need of changing any of the above parameters is by
stretching the coil current zero crossing. This principle is
also used in AMIS−3062x (see www.onsemi.com
) and is
called MinSamples. See Application Note AND8371/D for
more info on this.