Driver For Bipolar Stepper Motors

0 DRIVER FOR BIPOLAR STEPPER MOTORS For some applications, the Universal control for stepper motors (see in) may be considered too extensive a circuit. Many small motors with limited speed range can be equally well controlled by a relatively simple circuit, based on, for instance, the Type SAAI027 or TEA1012 121. Most commercially available con- trollers are, however, intended for driv- ing unipolar stepper motors, which are now gradually superseded by bipolar types of similar size. In practice, the lat- ter can provide a larger torque, but re- quire a different type of controller. The recently introduced Type MC3479P from Motorola requires a minimum of external components for controlling a bipolar stepper motor. The maximum quiescent stator current, Is, depends on the value of resistor R between pin 6 and ground: Is = (Ub-0.7)/0.86R [mA] where R is given in kQ. The above rela- tion between Is and R is valid as long as the output transistors are not operated in the saturated area....