Overview
A modern motor control design needs three things: knowing where the rotor is, driving the coils with the right current and protecting the electronics from a fault. Allegro MicroSystems builds the magnetic sensors that measure the position, the integrated drivers that move the motor and the current sensors that close the loop, and BeiLuo supplies them with genuine traceability and FAE support. This page shows how the parts fit together across stepper, brushed DC and brushless motor control.
Position Feedback
Position feedback starts with a magnet and a Hall-effect sensor. A small target magnet turns with the rotor or moves with the stage, and a linear Hall-effect sensor such as the Allegro A1324 converts the field into an analog voltage proportional to the position. Because the output is ratiometric, it tracks the supply and stays consistent for an ADC that shares the same reference. For a rotary measurement, two sensors placed in quadrature give the direction as well as the position, and a pair of sensors in the right geometry gives a usable angle.
Hall-Effect Commutation
In a brushless DC motor the rotor position decides which coil to energize, and Hall-effect sensors are the classic way to provide it. Three sensors spaced around the stator give the six commutation states directly, or a linear sensor on a target magnet can give a continuous angle for a field-oriented control loop. The wide -40 °C to +150 °C range of the Allegro sensors suits a motor that runs hot.
Stepper Control
A stepper motor needs a driver that sequences the coils, and the Allegro A4988 integrates the control logic and the DMOS power stage on one die with a built-in translator, so the controller sends only a step pulse and a direction. The driver supports full, half, quarter, eighth and sixteenth step modes, which smooths the motion and improves the low-speed accuracy. The A4988 drives up to 35 V and ±2 A and includes a fixed off-time current regulator.
Microstepping and Current Decay
Microstepping divides each full step into smaller increments, and the current decay mode decides how the driver returns the coil current to the target. The A4988 selects the decay automatically and can operate in slow or mixed decay, and the mixed mode reduces the audible noise and the step error. Set the current limit with the sense resistor and the reference voltage so the coil current stays within the motor rating.
Brushed DC Control
A brushed DC motor needs a full bridge to control the speed and the direction, and the Allegro A4950 integrates the bridge with the control and the protection. It drives up to 40 V and ±3.5 A peak with an adjustable PWM current limit and internal synchronous rectification to lower the dissipation, and the K grade is AEC-Q100 Grade 1 qualified for automotive use. The bridge handles the motor lead short to ground or to the supply without damage.
Current Sensing in the Loop
The motor current tells the controller the torque and the load, and it enables a current limit, a stall detection and a closed-loop control. An Allegro isolated Hall-effect current sensor such as the ACS712 measures the current with 2.4 kVRMS isolation and no shunt, so the measurement is safe and the insertion loss is low, and the output is proportional to the current for the ADC to read.
Choosing the Range
Choose the smallest current range that covers the maximum motor current, because a lower range has a higher sensitivity and a better resolution. The 5 A version gives 185 mV/A, the 20 A version 100 mV/A and the 30 A version 66 mV/A, all in the same package so a board can be retuned by swapping the part.
Protection and Thermal Design
Both drivers include over-current, short-circuit, under-voltage lockout, crossover-current protection and thermal shutdown, so a fault does not damage the driver or the motor. The thermal design still matters, because the driver dissipates power in proportion to the current and the on-resistance, so solder the exposed thermal pad to a good ground plane with enough copper area and provide airflow for a continuous duty.
Getting Help
Send your motor type, supply voltage, current, position requirement and environment to our FAE team and we will propose a driver and sensor set, help set the current limit and the magnetic circuit and review the layout. BeiLuo holds mainstream Allegro sensors and drivers in regional warehouses and ships every order with an import declaration, a certificate of origin and a RoHS compliance file, so a motor control design can move from prototype to production without a supply gap.