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LED driver features on-chip oscillator for programmable brightness control

Worcester, Mass. — Allegro MicroSystems, Inc. has introduced a three-channel constant-current LED driver with an on-chip oscillator for programmable brightness control. The A6281 driver is typically used to drive a cluster of red/green/blue (RGB) LEDs for one pixel in a large display or a lighting fixture.

The A6281 precisely controls LED brightness via 10-bit pulse-width modulation (PWM) per channel, complemented by 7-bit analog current control per channel to adjust color balance. The device drives up to 150 mA per channel and operates from a supply voltage of up to 17 V. Applications include large video displays and signs and architectural and decorative lighting.

The maximum supply voltage of 17 volts allows series strings of up to four or more LEDs on each output. An on-chip voltage regulator supplies the internal logic and reduces the number of external components and connections.

Control data is loaded serially, minimizing the number of pins on the device and the package size, said Allegro. Only four control signals are needed: Clock, Serial Data, Latch, and Output Enable. An innovative clock regeneration scheme allows large numbers (hundreds, depending on clock frequency and pixel spacing) of devices to be daisychained. Pixel spacing can range up to 3 meters (10 feet).

The A6281 requires only three external components to operate: a resistor to set the maximum output currents and decoupling capacitors for the on-chip voltage regulator and LED supply voltage. Housed in a 3 x 3-mm QFN package, the A6281 is available in the “E” extended temperature range of -40°C to +85°C.

Pricing: $0.78 in quantities of 1,000
Availability: 12-week typical lead time
Product information: A6281

Allegro MicroSystems, Inc. , www.allegromicro.com

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