User Manual

AND8399/D
http://onsemi.com
4
Below oscilloscope plots display the coil currents and the
SLA voltage measured at 1/8 microstepping. In the first plot
(Figure 7) no offset is created resulting in a microstep
position on the “coil current zero crossing”. The voltage
measured on the SLA−pin will represent the real Bemf
voltage of the stepper motor.
In the second plot (Figure 8) an offset is created. No
microstep position is located on the “coil current zero
crossing”. The voltage measured on the SLA−pin will not
represent the real Bemf voltage of the stepper motor.
Figure 7. Oscilloscope Plot of 1/8 Microstepping with Microstep
Position Located at the Zero Current Crossing
Y−coil
X−coil
Y−coil
V
SLA
Microstep position is located
at the zero current crossing
(= full step position).
The measured SLA voltage
(V
SLA
) will be a correct rep-
resentation of the Bemf
voltage.
“Coil current
zero crossing”
V
SLA
X−coil