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Motor driver IC takes a turn down brushless avenue

Posted: 03 Feb 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Vincent Biancomano? Apex Microtechnology? motor driver IC? dc brushless motor?

Responding to the growing number of motor control IC applications, Apex Microtechnology Corp. has released a motor driver IC for dc brushless motors that's said to be both powerful and versatile. A second chip provides much of the same advantages for brush-style motors.

The SA305 is Apex's first motor driver IC with a pulse-width modulator topology for dc brushless motors. It delivers up to 300W for three-phase applications-double the power capability of the nearest competing single-chip device, according to the company. It's also billed as the only brushless motor driver that offers designers their choice of digital interface, either DSP or MCU drive. The second chip, the SA56, delivers up to 250 W and brings similar gains for dc brush and stepper motor applications.

The SA305, which is a part of the company's Precision ICs collection of devices, is a bipolar-CMOS-DMOS digital chip targeted for motors in the fractional one-third-horsepower range. It includes gate driver circuitry driven by PWM inputs (that is, PWM is external to the chip), and an output stage utilizing three independent half-bridges.

The PWM approach (100kHz operation) gives designers better thermal efficiency and cuts real estate requirements for the higher-reliability brushless motor applications now gaining favor. The half-bridges deliver up to 5A, or 10A peak, with a 60V supply, for the motor. All six FETs (two per half-bridge) can be accessed independently to control the PWM and commutation. As for protection, Apex says the SA305 is the only 5A brushless motor driver with three-phase current monitoring.

At the same time, it's cost-competitive with discrete solutions, said Sam Robinson, senior applications engineer, though he noted the chip's prime objective is to provide greater flexibility than any other single-chip device now available. In this case, Robinson said, the chip's closest IC competitor in terms of power handling is STMicroelectronics' L6235, a device in the 50V range rated for an output of about 150W.

The SA56, with the same general specifications, is a bipolar-CMOS-DMOS device for dc and stepper motor drives. This chip includes a PWM that handles both analog and digital inputs, comparator circuitry, a gate driver, control and protection circuitry, and two half-bridges at the output.

In orders of 10,000, the SA305 is priced at $13.10 each and the SA65 at $8.90.

- Vincent Biancomano

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