Allegro introduces a new three-channel constant current LED driver with an on-chip oscillator for programmable brightness control. A typical application is to drive a set of red/green/blue (RGB) LEDs for one pixel in a large display or photographic device. The brightness of the LED can be precisely controlled by 10 bits per channel of pulse width modulation (PWM), and the 7-bit analog current control compensation per channel is used to adjust the color balance. Allegro's 6271A drive current is up to 150mA per channel and operates up to 17V. Can be applied to large video displays, signage and architectural and decorative lighting.
A maximum operating voltage of 17V can be connected in series with up to 4 or more LED strings at each output. An on-chip voltage regulator provides internal logic and reduces the number of external components and connections. The control data is serially downloaded, thus minimizing the number of pins and package size of the device. Only four control signals are required: clock, serial data, latch and output enable signals. These signals are buffered into slices to drive the next pixel in the cascade cascade. A novel clock regeneration architecture allows for a large number (hundreds, depending on clock frequency and pixel space) of devices connected in series. The pixel space can range up to 3m (10 feet).
The A6281 requires only three external components to configure: a resistor to set the maximum output current, the on-chip regulator's decoupling capacitor, and the LED operating voltage. High integration and a tiny 3 x 3mm QFN package make the board design even more compact. Allegro's A6281 has a temperature range that extends from -40°C to +85°C.
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