As shown previously, in voltage mode, the Back EMF must be known. Hence, a Back EMF compensation must be performed. If not performed, the current decreases as the motor spins faster. When the powerSTEP01 drives the motor, by using the motion engine, the device knows the speed of the motor, and the Back EMF that is proportional to the speed of the motor. In real time, it can calculate what voltage to apply in order to get a stable current. The faster the motor spins, the higher the applied voltage is.