An 8-Bit Current-Mode Digital-to-Analog Converter with Calibration Technique for AMOLED Display Drivers

This work presents the design and implementation of an 8-bit current-mode digital-to-analog converter (DAC) with a built-in calibration mechanism for active-matrix organic light-emitting diode (AMOLED) display drivers. Due to variations in thin-film transistor threshold voltage and mobility, AMOLED panels suffer from current non-uniformity and luminance degradation, necessitating accurate current sources with high channel-to-channel uniformity. The proposed current-mode DAC employs a channel calibration technique based on a two-step coarse/fine adjustment, utilizing a successive approximation register control loop and current comparator with correlated double sampling to mitigate offset. A 52-channel prototype was fabricated in a 0.18-μm CMOS process, occupying 0.00918 mm2 per channel and consuming 7.2 μW. Measurement results demonstrate a maximum differential nonlinearity of 1.3 LSB and integral nonlinearity of 1.8 LSB.