In this paper, a compact high-precision digital pulse-width modulation (DPWM) CMOS circuit is proposed. The circuit, with multiple output capability, allows brightness control of red, green, and blue (RGB) light emitting diode (LED) lighting. The PWM technique is used for LED dimming control to avoid the problem of color shifting. In this design, complementary concepts and hardware sharing are utilized to achieve a compact architecture and small chip area. A double-edge triggered technique is adopted to enhance the capability of high-speed operation. An experimental chip has been realized by using TSMC 0.18-mu m CMOS technology. Simulation results show that the proposed 5-bit PWM circuit can operate at 200 MHz, 32 duty cycles adjustable, and within only 1-ns time error. The chip's measured results show that the new PWM circuit with three output channels works successfully at a supply voltage of 1.8-V, clock of 50-MHz, and resolution of 32 adjustable per channel. The core area of the chip is only 280 x 52.5 mu m(2).
