Most traditional LED drivers are designed for the single-color LEDs, in which the high-resolution PWM generator is used for intensity control only. However, for RGB LEDs, both the color mixing and intensity control must be addressed to achieve the target effect. With the traditional solution, the users must handle the color mixing and intensity control simultaneously with a single PWM register. Several undesired effects occur: the limited dimming steps, the complex software design and the color distortion when using a logarithmic scale control.

The LP50xx device is designed with independent color mixing and intensity control, which makes the RGB LED effects fancy and the control experience straightforward. With the inputs of the color-mixing register and the intensity-control register, the final PWM generator output for each channel is 12-bit resolution and 29-kHz dimming frequency, which helps achieve a smooth dimming effect and eliminates audible noise. See Figure 8-1.

Figure 8-1 PWM Control Scheme for Each Channel