A 12-bit segmented resistor-capacitor digital-to-analog converter for a display driver IC of a large TFT-LCD panel system

Abstract

A 12-bit segmented R-C DAC to support a linear gamma curve has been proposed and fabricated in a 720-channel LCD source driver with a 16-V 1-poly 3-metal high-voltage CMOS process. The proposed DAC has a global resistor string and sample-and-hold buffers. A MSB voltage selected by the upper 6 bits of input data and a LSB voltage selected by the lower 6 bits of input data are summed by using a sample-and-hold operation with offset cancellation in the proposed DAC. The measured DNL was less than 0.3 LSB, and the output voltage deviation was less than 3 mV in all gray levels. Although two sample-and-hold buffers were adopted to operate alternatively, the die size was as small as 24.9 mm(2), which was only an 8.3% increase compared to that of a conventional 8-bit 720-channel source driver. Because of its good performance with small area, the proposed DAC can be a good low-cost solution for a 10-bit TV system