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Brushless DC motor driver is fully integrated

Posted: 06 May 2008 ?? ?Print Version ?Bookmark and Share

Keywords:brushless DC? motor driver? PWM control?

Allegro has introduced two new full-bridge motor drivers designed to drive low-voltage brushless DC motors in applications that require rotor speed control and fast rotor start-stop cycles. A high-density CMOS semiconductor process allows the integration of a Hall element, an H-bridge output driver and PWM speed control logic into a monolithic IC.

This fully integrated single-chip solution provides enhanced reliability including reverse battery protection and output shortcircuit protection. The small package outline and low profile make this device suited for use in applications where PCB area and component headroom are at a premium.

Commutation of the motor is achieved by use of a single integrated Hall element sensor to detect the rotational position of an alternating-pole ring magnet. Low-voltage design techniques have been employed to achieve full device functionality down to 1.8V VDD. The voltage applied to the PDC pin is used to externally control the maximum speed of the motor by adjusting the internal PWM duty cycle of the output driver.

Allegro's A1444/A1445 devices employ a soft-switching algorithm to reduce audible switching noise and EMI interference. The A1444 and A1445 have different, selectable internal PWM Duty Cycle options to accommodate a wide range of motor designs by controlling the state of the PDC input pin, providing external control. The externally controlled speed regulation and braking functions can be used to create motor designs with faster acceleration and stopping times. Each device has a braking function enable pin that also includes a micro power sleep mode for battery management in portable electronic devices. This feature allows for the removal of a FET transistor for switching the device on and off. The devices are optimized for vibration motor applications that require fast start-stop cycles, as in cellular phones, pagers, and hand-held video game controllers. These devices can also be used for low-power fan motors rated at 5V.

Targeted at the communication and consumer markets, Allegro's A1444 and A1445 motor drivers are available in a Pb-free (leadframe plating Nickel Palladium) 6-pin MLP micro-leadframe package for surface mount assembly. The underside of the package also features an exposed pad for enhanced thermal dissipation.

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