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Allegro LED driver IC
New three-channel constant-current LED driver IC from Allegro Microsystems has an on-chip oscillator for simple programmable brightness control.
The A6281 device is ideally suited to driving clusters of red/green/blue (RGB) LEDs in applications where the cluster forms one pixel in a large display or a lighting fixture. It precisely controls LED brightness via 10-bit PWM on each channel, complemented by 7-bit analogue current control on each channel to adjust colour balance.
The A6281 drives up to 150mA per channel and operates from a supply voltage of up to 17V, allowing series strings of four or more LEDs to be used 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, which minimises the number of pins on the device and the package size. Only four control signals are needed: clock, serial data, latch and output enable. These signals are buffered on the chip to drive the next pixel in a daisy-chained cascade.
The device 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 the LED supply voltage.