An Active-Matrix OLED Driver CMOS IC With Compensation of Non-Uniform Routing-Line Resistances in Ultra-Thin Panel Bezel

This paper presents a source-driver IC that actively compensates for inter-channel charging rate mismatch in an active-matrix organic light-emitting diode (OLED) display with ultra-thin bezel panel. Due to the limitation of the physical design, the resistances of the driver-to-column routing lines in the panel bezel differ across channels. To solve the luminance non-uniformity caused by resistance mismatch, a digitally controlled <inline-formula> <tex-math notation="LaTeX">$\text{g}_{m}$ </tex-math></inline-formula>-degeneration technique embedded in the output buffer amplifier is proposed. Each driver channel independently compensates for different routing-line resistances, resulting in a charging rate with excellent uniformity. In addition, the bezel area can be desirably minimized without a zigzag wiring pattern. The prototype 240-channel source-driver IC was fabricated using 0.18-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS technology, and offers a 16.8M-color depth with 13-mW power consumption. With a real OLED display, the measured luminance uniformity under condition of 240-Hz frame rate was improved from <inline-formula> <tex-math notation="LaTeX">$\sigma =1.43$ </tex-math></inline-formula>% to <inline-formula> <tex-math notation="LaTeX">$\sigma = 1.01$ </tex-math></inline-formula>% by the proposed scheme. The inter-channel output deviation was measured to be ±2.7 mV. The video play on 2.4-in OLED panel using a frame rate of 240 Hz was also successfully demonstrated with high display quality.