8.3.1.3.1 PWM Generator

With the inputs of the color mixing and the intensity control, the final output PWM duty cycle is defined as the product obtained by multiplying the color-mixing register value by the related intensity-control register value. The final output PWM duty cycle has 12 bits of control accuracy, which is achieved by a 9 bits of pure PWM resolution and 3 bits of dithering digital control. For 3-bit dithering, every eighth pulse is made 1 LSB longer to increase the average value by 1 / 8th. The LP503x device allows the users to enable or disable the dithering function through the PWM_Dithering_EN register. When enabled (default), the output PWM duty-cycle accuracy is 12 bits. When disabled, the output PWM duty-cycle accuracy is 9 bits.

To eliminate the audible noise due to the PWM switching, the LP503x device sets the PWM switching frequency at 29-kHz, above the 20-kHz human hearing range.