What Is a Motor Controller? Types, Functions and Selection

A motor controller manages how an electric motor starts, stops and runs. Depending on the system, it regulates direction, speed, torque or position and handles faults. Its implementation can range from switching equipment to an electronic control board with firmware, sensors and a power stage matched to the motor.

Motor controller vs motor driver: what is the difference?

The controller decides what the motor should do; the driver provides the switching and current needed to make it happen. A gate driver operates power-transistor gates, while a motor-driver IC may integrate the power switches. Commercial products often combine these functions, so the names alone do not establish what a device includes.

An external microcontroller might calculate a speed loop and send PWM commands to a driver. An integrated BLDC device can include the commutation algorithm. At larger power levels, the control electronics may command a separate inverter. Always read the functional block diagram and interface description.

Browse Motor Drivers, Controllers by motor type and integration level. A package that fits the PCB does not establish compatibility with the motor or its control method.

Which motor controller type matches your motor?

A brushed motor commutates mechanically. A BLDC motor requires electronic commutation. A stepper drive controls winding current in a sequence, often using microstepping. These differences prevent a generic voltage-and-current match from being sufficient. Manufacturer motor-control resources cover the distinct control approaches. [1]

For a component example, ChipApex lists 0C621-003-XTD in its motor-driver catalog. Treat it as a part-number-specific sourcing route: verify its original datasheet and microstepping interface before considering a replacement or a new design.

Why do startup current and stall current matter?

Motor current changes with mechanical load and operating state. A brushed DC motor has little back electromotive force at standstill, so startup can demand much more current than steady running. A blocked shaft can sustain a damaging load unless the drive limits current or disconnects it.

For a simplified brushed-motor estimate, stall current is supply voltage divided by winding resistance. An illustrative 12 V motor with 2 Ω winding resistance would draw about 6 A at stall before accounting for driver drops, wiring and temperature effects. This is a calculation, not a tested motor rating. Use the manufacturer’s data or controlled measurement for the real design.

A peak current headline also needs a duration. Check the driver’s continuous thermal capability, current-limit behavior, PCB requirements and protection timing. Current limiting can constrain available starting torque. Thermal shutdown protects against some overload conditions but should not be the normal operating control. [2]

PWM, feedback and microstepping: which function controls what?

PWM changes switching duty cycle. In a simple brushed-motor drive it influences the applied average voltage, but the resulting speed still depends on load. Closed-loop speed control measures actual speed and adjusts the command. Position control additionally needs a position reference or an appropriate estimation method.

Microstepping sets intermediate winding-current levels in a stepper motor. It can improve motion smoothness, although commanded microsteps do not guarantee equal mechanical position increments under every load. Check acceleration, resonance, torque margin and missed-step detection where position matters.

For BLDC drives, sensored and sensorless approaches have different startup and low-speed behavior. Choose the control method around required torque, acoustic behavior and feedback availability. Firmware tuning can be part of the component integration effort.

How should you handle braking and motor-driver protection?

Stopping modes change the power flow. Coasting allows the motor to slow with relatively little commanded braking torque. Dynamic braking dissipates energy in a defined electrical path. Regenerative operation can return energy to the supply, which must be able to accept it or have another way to limit the bus voltage.

Do not assume a bench supply can absorb returned energy. Check bus capacitance, transient suppression and the drive’s recommended braking arrangements. The appropriate solution depends on motor energy, inertia and stopping frequency.

Protection checks should include undervoltage, overcurrent, short circuits, thermal limits and fault reporting. External MOSFET stages also need appropriate switching control to prevent simultaneous conduction in a half bridge. Follow the chosen device’s layout and decoupling instructions; high-current loops and sensing connections affect operation. [3]

A motor controller selection workflow

First identify the exact motor and required motion profile. Record minimum and maximum supply voltage, including transients. Establish running current, startup requirements and credible stall conditions. Then choose feedback, command interface and stopping behavior.

Compare the full current path, including power switches, shunts, connectors and PCB copper. Validate at the highest intended enclosure temperature and under the actual duty cycle. Test startup under load and controlled fault recovery, with a setup that prevents uncontrolled movement.

Finally confirm the complete ordering code, package and supported development tools. Replacing an older driver may require changes to current sensing, firmware or pin assignments even when its nominal supply rating appears similar.

Motor controller FAQ

Can one controller drive any motor?

No. The commutation method, number of phases, current regulation and feedback requirements must match. A brushed DC H-bridge does not by itself provide the three-phase sequence required by a BLDC motor.

Is a motor controller always programmable?

No. Some accept simple logic, PWM or step-and-direction commands. Others contain configurable control algorithms or run user firmware. Check which functions are fixed, register-configured or software-defined.

Should the controller rating match the motor’s running current?

Running current is only part of the requirement. Include startup, acceleration, braking and stall behavior, along with permitted duration and current limiting. Verify the thermal conditions behind the stated continuous rating.

Does a motor driver need cooling?

It depends on loss and the available heat path. PCB copper, exposed-pad layout, airflow and ambient temperature can limit continuous output. A driver that survives a short bench run may still overheat in an enclosure.

What details help ChipApex identify candidate parts?

Provide the full motor or existing driver part number, motor type, supply range, phase or stall current, feedback method and command interface. Include package constraints and quantity. Candidate parts still require datasheet and application checks before substitution.

References

1. Texas Instruments: Motor-control technologies and reference designs
2. Texas Instruments: Understanding Motor Driver Current Ratings
3. STMicroelectronics: VNHd7xxAY H-bridge drivers application note