A High 6318-PPI Pixel Circuit That Realizes 10-bit Gray Levels for Analog-PWM Driven Micro-LED Displays

Shih Song Cheng, Paul C.P. Chao*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


A new pixel circuit is proposed to realize 10-bit gray levels for high 6318 pixel-per-inch (PPI) micro-light-emitting-diode (micro-LED) displays, with a ramping voltage varied from high to low, outputting a pulse-form pixel current ( {I}_{text {pixel}}{)} , while the pulsewidth of this {I}_{text {pixel}} can be modulated with two data voltages ( {V}_{text {data}} 's). The first {V}_{text {data}} is inputted and varies along the main 7-bit emitted grays, and the extra 3-bit gray levels are expanded as the second {V}_{text {data}} joins on the basis of the original 7-bit. Therefore, these 10-bit grays with the maximum 7-bit {V}_{text {data}} are realized in a smaller {V}_{text {data}} range ( {R}_{text {DATA}}{)} as opposed to a conventional 10 bit obtained with a 10-bit {V}_{text {data}}. The proposed circuit was fabricated in the pixel array of 6318PPI via the 55-nm CMOS process. The actual {R}_{text {DATA}} of 0.635 V allows this circuit to be able to majorly constructed by the 1.2-V low-voltage field-effect transistor (LVFET), differing from the conventional 10-bit that is realized in {R}_{text {DATA}} of above 5 V by all high-voltage FET (HVFET)-made pixel circuits, that is, the circuit composition of LVFET substituting for HVFET is in favor of the layout shrinking of a pixel, offered the advantage of this technique on high PPI. Based on the experiments, the gamma-corrected 8-bit trimmed from the outputted 10-bit grays shows a favorable result that the obtained gamma distributes within 1.99 and 2.26 with standard deviation sigma & of 0.03, successfully validating the proposed high PPI pixel circuit for realizing 10-bit gray levels.

Original languageEnglish
Pages (from-to)1122-1130
Number of pages9
JournalIEEE Transactions on Electron Devices
Issue number2
StatePublished - 1 Feb 2024


  • 10-bit grayscale
  • analog pulsewidth modulation (A-PWM)
  • data voltage range (Vdata range)
  • high PPI
  • micro-LED
  • microdisplays
  • pixel circuit


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