Paper

Random Noise Improvement for Pixel-Parallel Single-Slope ADC

2025 Jun

Authors Masayuki Uno *, Kwuang-Han Chang**, Tsung-Hsun Tsai ***, Toshiyuki Isozaki*, Rimon Ikeno*, Kazuya Mori*, Ken Miyauchi*, Yi-Hsuan Lin**, Sheng-Yeh Lai **, Chih-Hao Lin**, Wei-Fan Chou*, Junichi Nakamura*, Guang Yang**, Song Chen*** and Chiao Liu***

2025 International Image Sensor Workshop (IISW)
https://imagesensors.org/2025-international-image-sensor-workshop/

Low random noise (RN) design for pixel-parallel single-slope ADC (SS-ADC) in digital pixel sensor (DPS) is reported. The AC-based RN estimation with respect to the comparator bias current and bandwidth-limiting capacitor in DPS is discussed. RN is composed of thermal noise (TN) and flicker noise (FN), and FN easily becomes the major contributor in DPS. Low RN design comparable to that in digital correlated double sampling (D-CDS) scheme is considered after studying FN characteristics modulated by CDS operation. High gain single-ended comparator is introduced to realize area-efficient DPS. It achieved the low RN of 2.4e-rms in 3.24um pixel by 10-bit in-pixel memory without D-CDS. High dynamic range (DR) was demonstrated using dual quantization operation with 2 conversion gains in single exposure.