A 5.6mV inter-channel DVO 10b column-driver IC with mismatch-free switched-capacitor interpolation for mobile active-matrix LCDs

Abstract

To achieve high image quality in mobile active-matrix LCDs, higher DAC resolution and good channel-to-channel uniformity are required in column-driver ICs. In conventional column-driver ICs, the resistor-DAC (R-DAC) architecture has been generally used due to its uniform characteristic, because each R-DAC in driver channels shares a common resistor string for gamma reference-voltage generation. Furthermore, nonlinear gamma correction can be easily implemented using a nonlinear resistor-string that has an inverse transfer curve to the liquid crystal (LC) response. However, the increase in color depth for LCDs results in a large chip-size overhead, thus disclosing the limitation of the R-DAC architecture. To overcome this issue, several hybrid DAC architectures composed of a main 6b R-DAC and a 4b sub-DAC with various interpolation schemes have been reported [1-5]. Their linear interpolation schemes reduce the driver channel size. Meanwhile, their linear 4b interpolation leads to the loss of effective bit resolution for nonlinear gamma correction. In addition, the inevitable mismatch between respective sub-DACs has a significant influence on the channel-to-channel uniform performance of a column-driver IC. In this paper, we present a 10b column-driver IC with a mismatch-free switched-capacitor (SC) interpolation scheme for mobile AMLCDs. The proposed mismatch-free interpolation scheme provides further reduction of the driver size, good linearity, highly uniform channel performance, and more effective bit resolution.