A 10-Bit Low-Power High-Color-Depth Column Driver with Two-Stage Multi-Channel RDACs for Small-Format TFT-LCD Driver ICs

This study proposes a 10-bit low-power high-color-depth LCD column driver IC with two-stage multi-channel RDACs and switch resistance compensation. The design removes intermediate buffers from two-stage RDACs and uses global reference buffers to isolate the global resistor string and output channels. Because the global resistor string is isolated from output channels, the global resistor string can use a larger resistance value to achieve lower power consumption. This study proposes a class-AB buffer for the global reference buffers to compensate for the errors caused by the voltage drop on switches connected in series with the channel resistor string. The channel resistor strings also reuse the output stage current of the global buffer to reduce power consumption. A prototype of a 200-channel column driver was fabricated using 0.18-\mum/0.35-\mum CMOS technology with the worst DNL/INL being 1.2/1.1 LSB. The proposed 10-bit DAC occupies only 66% of the area of a conventional 8-bit RDAC using the same technology. The 200-channel column driver consumes a total static current of only 0.38 mA.