With the number of motion-control systems in automotives and the industrial floor still on a steep incline, vendors are racing to market with a slew of controller ICs and modules largely intended for driving today’s motor of choice: The brushless DC (BLDC). They’re also offering more advanced BLDC reference designs. Several new general driver chips, although not motor driver ICs in their own right, add to the strong supporting cast. A cross section of the latest motor-drive products, many of which focus on stepper-motor, variable-speed applications and associated digital topologies (while avoiding more complex DSP solutions where possible), underscore the unified effort to secure more accurate and reliable systems.
Brushless motors and the IC-to-motor connection, a natural result of the technology’s gradual migration from the mechanical to the electrical domains, generally take up much less real estate. Operationally, brushless motors tend to cut EMI as well as audible noise. A snapshot of the latest motor-drive IC products shows Apex Microtechnology’s (Tucson, Ariz.) SA305 in the lead for power. At 300 watts (fractional one-third horsepower range), it’s reportedly the industry’s most powerful and versatile driver by far for BLDCs. In a departure from the company’s previous motor controllers, which use power op amps or hybrids, it’s the company’s first using PWM topology. Its design includes gate circuitry driven by PWM inputs (PWM source external to the chip), and an output stage using three independent half-bridges. A second chip, the SA56, with the same general capabilities as the SA305, includes a PWM generator and is suited for 250-watt DC and stepper-motor applications.
Other high-power entries include Fairchild’s (South Portland, Maine) Motion-SPM “smart power” modules for under 200-watt inverter (AC) motors, the FCBS0550 and FCBS0650, which are suited to applications in refrigeration and the like. These 500- and 600-volt rated modules integrate six MOSFETs, three high voltage ICs and one low-voltage IC. Development software for reference designs is available at the company website.
High-power applications aside, the newest arrivals are packed with a fair degree of flexibility and innovation. Allegro’s earlier (Worcester, Mass.) half-bridge pre-driver, the A3946, is designed for three-phase brushless DC motors, brush DC motors, switched-reluctance motors and for other industrial and automotive applications that otherwise present a large inductive load. Other chips include Allegro’s A3949, billed as one of the smallest most cost-effective high-current DMOS drivers available for DC motors. The driver, working from a single supply, delivers up to ±2.8 amps at 36 volts. The company's latest full-bridge driver chip, the A3950, complements the family.
Allegro’s A1441 is the first full-bridge DC brushless motor driver IC that includes a Hall commutation element. It’s suited for single-phase, low-voltage motors in consumer applications. No external components are required (one bypass capacitor is recommended). The ZXBM1015 motor pre-driver IC from Zetex (Hauppauge, NY) is designed for variable for fixed speed control of single-phase DC brushless motors driving fans, blower, and pumps. It’s the first IC, according to Zetex, to offer a configurable phase commutation delay to allow OEMs to meet the requirements of different motor sizes. In addition, it features an adjustable minimum-speed setting that also prevents the motor from not being able to start.
Two steps forward, one step to the right
Devices targeted for stepper-motors, many of which can be implemented with BLDCs, continue to draw the most applications-specific activity. Allegro’s SLA707xMPR is suited to unipolar two-phase applications. Available in 16 versions to provide 1 to 3 amp service, the family touts the most comprehensive set of features among unipolar drivers, including overall lower power dissipation and protection against a shorted or open/disconnected motor.
Allegro’s A3979, a microstepping motor driver for bipolar stepper motors with built-in translator, is touted as superior to most microcontroller-based systems for multiple-motor applications. It operates in full-, half- quarter-, and sixteenth-steps. This chip can operate in a mixed-decay current mode to reduce a system’s audible noise. A similar chip for simpler designs, the A3982, is suited to full- and half-step increments.
AMI Semiconductor (Pocatello, Idaho) says its AMIS-30621 and -30622 stepper-motor controllers, for automotive applications, are the industry’s smallest. These chips, which integrate the features required for bus connectivity and stepper motor control in a 32-pin near chip-scale sized package, are suited to remote and multiple axis positioning using a local interconnect network, or requiring serial connectivity, respectively.
For consumer applications and portable electronics, Freescale’s (Tempe, Ariz.) MPC17C724 is a dual-channel motor driver IC for bipolar step motors that delivers 400 mA per channel for controlling the camera lens and shutter. The H-bridge IC has four control modes: forward, reverse, brake, and tri-state (high impedance). A similar entry, Rohm Electronics’ (San Diego, Calif.) BD6735FV is a 2-channel H-bridge driver for both DC and stepping motors for lens driver applications in digital still and digital video cameras.
Several chips, though not motor IC drives unto themselves, have arrived to boost motor control applications. These include Power Integrations’ (San Jose, Calif.) PeakSwitch, a family of controller ICs for power supplies specifically designed with peak, versus nominal, output in mind. One application is an inkjet printer that requires up to 80 watts on peaks in order to activate its paper-advance motor.
A higher power
Full "reference designs," in the form of so-called system “platforms” that most often imply graded families of motor-drive-with-processor boards and extensive software development tools, are becoming more available to aid the OEM designer. International Rectifier (El Segundo, Calif.) has extended its iMOTION platform with a new family of digital control ICs for variable-speed permanent-magnet motors, which are coming along as an alternative to AC induction motors especially in applications above 10 HP. Touting high efficiency (95 percent), the company’s IRMCF3xx family of digital control ICs includes an embedded analog signal engine that integrates signal conditioning for sensorless motor control applications.
STMicroelectronics’ motor driver platform, comprising separate device and design block offerings for steppers and brushless DC motors, include ten highly-integrated powerSPIN (L62xx) drivers rated at up to 5.6 amps, and a comprehensive support package (practiSPIN) that includes evaluation boards, PC software, and application notes. In addition, the company’s Motor Control Reference Design Kit , for AC and 3-phase brushless DC motors, includes a control board and three power boards with appropriate developmental tools that simplifies motor designs up to 3 kW.