WORKSHOP PAPER
Improvement of Fixed Pattern Noise and Electrical Cross-Talk in Small-Sized Pixel-Parallel ADCs
Abstract
This paper introduces the phenomenon and underlying causes of fixed pattern noise (FPN) and electrical cross-talk (XT) in small-sized pixel-parallel ADC and proposes an effective method to address these issues. Pixel-parallel ADC is a promising architecture that enhances key image sensor performance, including frame rate, noise, dynamic range, and power efficiency, compared to conventional column-parallel ADCs. Despite these advantages, the large size of the digital pixels remains a significant challenge, limiting its practical applicability and value. To reduce pixel size, we proposed a cluster-based structure. However, this approach introduced two major issues: cluster-induced fixed pattern noise (CL-FPN) in dark conditions and cluster-induced cross-talk (CL-XT) in illuminated conditions. CL-FPN arises due to dark offset errors in the M×N cluster configuration. On the other hand, CL-XT occurs at the boundary between bright and dark regions, where the output code value of a bright pixel inadvertently affects adjacent dark pixels, causing them to appear as white pixels. To identify the root causes of these issues, we performed precise circuit simulations and related measurements. Ultimately, we successfully mitigated the problems, and the simulation results were confirmed to align closely with the package measurements of digital pixel sensor (DPS).Keywords
CMOS Image sensor, global shutter, pixel-parallel ADC, pixel-level ADC, digital pixel sensor, cluster structure, cluster induced fixed pattern noise, cluster induced cross-talk,References
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