User Manual

AND8399/D

http://onsemi.com

Full Step Stepping Mode

All explanation given above is only valid if the stepping

mode is not set to full step. This is because after a hard reset

of the motor driver, full step mode will always start from a

half step position meaning that no microstep position will be

located on the “coil current zero crossing” (see also

Figure 1). Creating an offset on purpose to move the step

positions to a “coil current zero crossing” will not be

possible making Bemf measurement in this stepping mode

impossible.

There is however a possibility to operate the stepper motor

in full step mode and

measure the Bemf voltage. Follow next

steps to operate the stepper motor in full step mode by using

AMIS−305xx half step stepping mode setting.

1. Reset motor driver

2. Set coil current. Set the stepping mode to

compensated half step.

3. Enable the motor driver (stepper motor should be

located in a full step position)

4. Every time a full step has to be set, apply two

NXT−pulses fast after each other (keeping

NXT−pin limitations in mind).

In the next figure one can see that the stepper motor is

running in full step mode although the stepping mode of

AMIS−305xx is set to compensated half step. Because of the

relative high inductance of the motor, the very short time

between the two NXT−pulses (see zoomed part of

Figure 18) and the internal delay of the driver, the half step

position will never be reached on time. The stepper motor

will run in full step mode.