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longer-term continuous rotation. It is used in applications such as printers and positioning stages (just two of its many uses). Furthermore, even though positioning precision is a function of the number of poles, using an advanced technique where adjacent poles are partially turned on—called microstepping—allows the stepper to have much ner and well-controlled steps than the number of physical poles indicated. Motor-Control Chain Requires Strategy and Power Muscle A complete motor-control system consists of several functional blocks (Figure 4), including: The controller – The controller decides what the motor must do to meet the application's needs at a given instant and denes what power is necessary for which poles and when. This controller can be a xed-function dedicated IC, or it can be a part of a larger, rmware-based system. If the motor has a feedback loop— as many do, using a sensor at the rotor shaft—then the controller also assesses the motor's position and velocity versus the intended values, and it determines the appropriate changes essential for power control. • The output – The controller's output goes to gate drivers that translate the low-voltage and current on/off commands into higher currents (and often higher voltages) required by the MOSFETs (or IGBTs). This path may be galvanically isolated in many cases. • The MOSFETs (or IGBTs) – The MOSFETs (or IGBTs) are the actual power switches that control the current ow to the motor coils. • The motor coils – The current running through the motor coil windings generates an electromagnetic eld, which interacts with stationary magnets in the motor causing it to start to rotate. 16 Figure 4. The signal path for motor control begins at a low-voltage controller (which may be a programmable microcontroller unit (MCU) or a dedicated control IC). This low-voltage, then, passes through the gate drivers (with optional isolation, depending on the application) to control the MOSFETs or IGBTs—which are the on/off switches that direct current to the motor coils or poles. (Source: Mouser Electronics) Motor Controller Low-Voltage Signal Isolated Low-Voltage Signal Isolation Gate Driver(s) Gate Drive Motor MOSFET or IGBT Gates MOSFET or IGBT Output mouser.com/stm-powerstep01/ PowerSTEP01 System-in-package integrating microstepping controller and 10A power MOSFETs for superior smoothness and accurate positioning • Dual full bridge with R DS(on) = 16m • 10A r.m.s. maximum output current • Smoothness with up to 1/128 microsteps/step • Operating voltage: 7.5 - 85V • Easily programmable with SPI • Programmable speed prole and positioning • Adjustable output slew rate • Sensorless stall detection • Full set of protection functions

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