26.2 A Fully Nonlinear Compact 10b Source Driver with Low-Voltage Gamma Slope DAC and Data/Phase Dependent Current Modulation Achieving 2411μm2/Channel for Mobile OLED Displays

With the rapid development of display technology, there is a growing demand for high-color-depth, low-power, cost-effective, and compact source-driver ICs (SD-IC), which convert digital data to analog output to drive display panels. However, it is challenging to satisfy both high color depth and compact size because of the resistor digital-to-analog converter (RDAC) in conventional SD-ICs, whose silicon area exponentially grows as the DAC resolution increases. To overcome this issue, piecewise-linear interpolation methods have been studied by combining a nonlinear RDAC and sub-bit linear interpolation [1–5]. These methods can decrease the channel area by using a smaller-bit RDAC, but their piecewise-linear output voltages cannot fully cover the nonlinear gamma voltage range, degrading display quality as shown in Fig. 26.2.1 (top left). For example, to produce the same effective 10b color depth as a conventional SD-IC with nonlinear 10b RDAC, the RDAC with sub-bit interpolation requires 12b (or more) resolution to provide a whole range of gamma voltages, which further increases the channel area [6].