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A6281 3-Channel Constant Current LED Driver with Programmable PWM Control

Allegro Microsystems

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Product Description:
The A6281 is a 3-channel constant current LED driver that has a wide range of output currents. The A6281 controls LED brightness with a Pulse Width Modulation (PWM) scheme that gives the application the capability of displaying a billion colors in an RGB cluster. The maximum current is set by an external resistor.

The LED brightness is controlled by performing PWM control on the outputs. The brightness data of the PWM signal for each LED is stored in three 10-bit registers. The peak value for each LED can be adjusted (dot-corrected) to compensate for mismatch, aging, and temperature effects. All the internal latched registers are loaded by a 32-bit shift register. One address bit controls whether dot correction/clock divider ratio or brightness data is loaded into the registers. The remaining bits are used for the data.

The A6281 is designed to minimize the number of components needed to drive LEDs with large pixel spacing. A large number of A6281s can be daisy chained together and controlled by just four control signals (clock, serial data, latch, and output enable). Each of these inputs is buffered to drive the next chip in the chain. Also, VIN can be tied to the LED voltage supply bus, thus eliminating the need for a separate chip supply bus or an external regulator.

The A6281 is supplied in a 3 mm × 3 mm 16-terminal QFN (suffix ‘ES’) package, with 0.75 mm nominal overall height. The package is lead (Pb) free with 100% matte-tin leadframe plating.

Product Specifications:

* 3 × 10-bit PWM brightness settings
* 3 × 7-bit dot correction current settings
* 5 to 17 V operation
* Wide output current range, 10 to 150 mA per channel
* Internally generated PWM clock
* Serial port operates at up to 5 MHz
* Data and clock logic architecture allows single microcontroller control of large quantities of serially-connected A6281s at fast data transfer rate
* Buffered logic outputs to drive cables
* Thermal shutdown and UVLO protection
* Power-On Reset


* Colored, large-character LED signs
* Scrolling, colored marquees
* Architectural lighting
* High intensity monochrome displays
* Large video and graphic displays

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