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Allegro Introduces A New 3-Bit Constant Current LED
Driver With PWM Control
Minimize the Number of Components Needed to Drive LEDs with Large
Pixel Spacing 
Worcester, MA, November 14, 2006 — Allegro introduces a new 3-bit constant current LED driver with a broad range of output currents. Allegro’s A6280 device is designed to minimize the number of components needed to drive LEDs with large pixel spacing. Several A6280’s can be daisy chained together and controlled by four control signals (Clock, Serial Data, Latch and Output Enable). Each of these inputs has buffered outputs on chip. Also, the VIN pin can be tied to the LED voltage supply bus, thus eliminating the need for a separate chip supply bus or an external linear regulator. This new driver controls LED luminance with a Pulse Width Modulation (PWM) scheme that gives the application the capability of displaying a billion colors. An external resistor sets the overall maximum current.
Performing PWM control on the outputs controls the LED luminance. The luminance data of the PWM signal for each LED is stored in three 10-bit registers. Each LED can be dot corrected by a 7-bit scalar register that scales the maximum current from 100% down to 36.5%. A 31-bit serial shift register loads all the internal latched registers. One bit is used to control whether dot correction/clock divider ratio or luminance data is loaded into the registers. The remaining 30 bits are used for the data. This helps reduce the pin count of the A6280. To further lower the A6280 pin count, the PWM clock and the serial bus clock share the same pin and work concurrently to control LED luminance and to load data.
Allegro’s A6280 is supplied in a 16 lead dual in line package (suffix ‘A’) package and in a 16-lead MLP (suffix ‘ES’) package.
About Allegro
Allegro MicroSystems, Inc. is a global leader in the development, manufacture and marketing of high-performance power integrated circuits and integrated Hall-effect magnetic sensor ICs. Allegro’s innovative, system-level solutions serve high-growth applications within the automotive, computer/office automation, industrial, consumer and communications markets, while our leading-edge product and processes reinforce our expertise in motor driver and power management technology. In addition, we also hold leading positions within printer, scanner, copier and portable device (e.g. cellular phones) applications. With more than 2,400 employees, Allegro is headquartered in Worcester, MA. Further information about Allegro can be found at www.allegromicro.com.
Editorial Contact:
Stephanie Fennelly
Director – Marketing Communications
Tel: (508) 854-5363
sfennelly@allegromicro.com