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  • MCP1643 RGB LED Driver

  • Created: Jan 09, 2017

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Summary

An RGB LED is just similar to a one color LED except that it has three different colored LEDs housed in a single package. RGB LED has only four leads: one cathode for each color, and one common anode. By adjusting the brightness of each LED in an RGB LED, it is possible to produce more colors. A common method of doing this is through PWM of which the cycle duty range determines the available brightness levels. Apart from the popularity in applications like outdoor decoration lighting in cities, stage lighting designs, home decoration lighting and LED display matrix, RGB color mixing technology can also be found recently in LCD backlighting and projectors.


This reference design features the MCP1643 RGB LED driver from Microchip. This is capable of turning ON and OFF an RGB LED with a variable duty cycle applied to the EN pin. The maximum dimming frequency is only limited by the internal soft-start of 240us. In this design, MCP1643 device is used in a boost converter application supplied by one AA battery, which drives each color of the RGB LED separately at a constant current of 350mA. A PIC microcontroller drives each color of the RGB LED at a frequency of 70Hz. The intensity of each color of the LED can be adjusted using individual potentiometers for each color. The RGB LED is driven by a microcontroller with three PWM signals, and by modifying the duty signal the duty cycle of each signal, the brightness of each color can be altered.


The MCP1643 is capable of starting up with a low voltage, while achieving high efficiency to drive one or more LEDs with constant current. This design is suitable for one and two-cell Alkaline and NiMH/NiCad portable LED lighting, LED flashlights, head lamps, wall LED lamps with motion detectors, LED supply for backlights, and other general LED constant current applications.

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