Nano-ampere Current Sensing Technique for OLED Mobile Displays

In this paper, we propose a nano-ampere current sensing technique for organic light-emitting diode (OLED) mobile displays. The nano-ampere current sensing system consists of a current integrator and an 8-bit single-slop analog to digital converter (SS-ADC). In order to reduce area and power consumption, the current integrator and a comparator of the SS-ADC share an amplifier, called differential difference amplifier (DDA). From the experimental results, we obtain 399.21 pA of accuracy with 8-bit current sensing resolution ranged from 0 to 102.2 nA. The proposed current sensing circuit was fabricated with a 90 nm CMOS technology and chip size is about 600 μm × 3000 μm.