A 7056-PPI Pixel Circuit With Low-Leakage Structure for Active-Matrix Monochrome Micro-LED Displays

Abstract

This work presents a 5T2C pixel circuit for active-matrix (AM) micro-displays in near-eye display applications. The circuit supports monochrome micro light-emitting diode (micro-LED) displays with ultrahigh resolution of 7056 pixels per inch (PPI). The circuit is designed and fabricated based on medium-voltage (MV) devices from the 55-nm high-voltage (HV) CMOS process. The total storage capacitance is only 6.588 fF, and the stored charge is susceptible to transistor leakage current, resulting in significant deviations in the average driving currents. To mitigate the deviations, the circuit isolates the switching transistor (TS) from the data signals, increases the body voltage for TS, and minimizes the body area of TS. The low-leakage structure effectively reduces off-leakage current (IOFF) and reverse-bias p-n-junction leakage current (IREV) of the transistors. Simulation results demonstrate that the proposed circuit produces slight current deviations compared to a conventional 2T1C circuit. Measurement results also confirm that the deviation rate is less than 6.23% for all gray levels (GLs).