Motor Driver Solutions vs. Building a Driver from Discrete Components

Motor drivers are necessary to control the electric motors found in everything from office printers to fans. As the applications for motors have increased in complexity, so has the functionality of a motor driver. While assembling motor drivers from discrete components has worked in the past, more engineers are turning full motor driver solutions that are contained on a single chip.

Understanding Motor Drivers

Motor drivers serve as the interface between a DC motor and its control circuit. These drivers take the low current signals received from the control circuit and amplify them to generate the high current signals needed to drive the motor. Various approaches have been used to create motor drivers through the years, with the H-bridge circuit being the most common. At a minimum, an H-bridge driver can turn motors on/off and reverse the direction of the motor. However, for more advanced applications such as robotic vacuums and SLR cameras, greater control and circuit protection become necessary.

Discrete Component Motor Drivers

The traditional approach to a motor driver is to assemble them from discrete components, with the most common being the basic H-bridge. The name “H-bridge” comes from the H-shaped configuration formed by the four switches that are central to its functionality. A basic H-bridge motor driver circuit typically includes four switches made from MOSFETs or P-channel and N-channel BJTs.

However, keep in mind that the H-bridge components described would comprise the bare minimum needed for a simple driver. Motor driver circuits become more complicated as efficiency, noise, vibration, circuit protection, and EMI become involved, and engineers must also give thought to input and output interfacing. In short, drivers for applications such as industrial printers or camera focus require far more than a basic H-bridge to function.

Example of a block diagram of a six-channel system lens driver for digital still cameras, which involves far more than a simple H-bridge.

Time spent designing customized drive circuits for various applications can be extensive, including the selection of discrete components, circuitry design, PCB layout, and extensive testing. And this effort can be wasted when there are motor driver solutions available that come pre-packaged with the necessary functionality and documented performance.

Benefits of Motor Driver Solutions

In a motor driver solution, the discrete components of the driver are integrated inside a chip, and these chips are thoroughly tested and documented to provide reliable, predictable performance. Using a driver solution also replaces the need to design and manufacture PCBs for motor control circuitry.

Motor driver solutions offer several benefits when compared to building a driver from discrete components. For example, they are straightforward to use and simple to implement, saving time during the design and testing phase. This approach also eliminates “reinventing the wheel” because there is no need to design a motor controller for each new product or application.

Motor driver solutions also provide excellent reliability, due in part to built-in protection schemes to prevent the failure due to faults (e.g., over-current protection circuit, thermal shutdown, undervoltage lockout) and the availability of performance data. This further simplifies the design and allows engineers to focus on other key features of the application involved.

There are also a variety of motor driver solutions developed for specific applications. For example, motor drivers are designed to meet the needs of the stepper motors or brush motors used in thermal printers that must be energy-efficient and compact.

Robotic vacuums require multiple motors, and each motor has specific needs in terms of the motor drivers.

The same is true for the low vibration, high accuracy demands of motors used in cameras, including the pan/rotate/tilt, shutter, and auto-focus functions. And for robotic vacuums, which need multiple motors to do their job, there are driver options that provide low noise and meet the power requirements involved with a battery-powered device.

Meeting Motor Driver Solution Requirements

There are several benefits that motor driver solutions have over building drivers from discrete components, including ease of use, time savings during design and testing, and the availability of application-specific solutions.

ROHM’s line of motor driver solutions offers general purpose and application-specific designs that are designed to provide excellent reliability and high efficiency over a range of voltages, currents, pin configurations, and package types. In addition, appropriate built-in protection circuits are included with each motor driver solution, further enhancing their reliability and that of the products that use them.

MOTOR DRIVER PRODUCT TRAINING MODULES FROM DIGI-KEY ELECTRONICS