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LED driver has on-chip oscillator for brightness control

Posted: 03 Sep 2007 ?? ?Print Version ?Bookmark and Share

Keywords:constant-current LED driver? oscillator? programmable brightness control?

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 1pixel in a large display or a lighting fixture.

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

The maximum supply voltage of 17V 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 daisy-chained. Pixel spacing can range up to 3m.

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 3mm x 3mm QFN package, the A6281 is available in the "E" extended temperature range of -40C to 85C.

Pricing for the device starts at 78 cents in quantities of 1,000. Delivery is 12-week typical lead time.

- Gina Roos
eeProductCenter




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