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A 6.9-<inline-formula> <tex-math notation="LaTeX">$\mu$ </tex-math> </inline-formula>m Pixel-Pitch Back-Illuminated Global Shutter CMOS Image Sensor With Pixel-Parallel 14-Bit Subthreshold ADC

2018; Institute of Electrical and Electronics Engineers; Volume: 53; Issue: 11 Linguagem: Inglês

10.1109/jssc.2018.2863947

1558-173X

Masaki Sakakibara, Koji Ogawa, Shin Sakai, Yasuhisa Tochigi, Katsumi Honda, Hidekazu Kikuchi, Takuya Wada, Yasunobu Kamikubo, Tsukasa Miura, Masahiko Nakamizo, Naoki Jyo, Ryo Hayashibara, Shinya Miyata, Satoshi Yamamoto, Yoshiyuki Ota, Hirotsugu Takahashi, Tadayuki Taura, Yusuke Oike, Keiji Tatani, Takayuki Ezaki, Teruo Hirayama,

Neuroscience and Neural Engineering

In this paper, we report on a back-illuminated, global shutter, CMOS image sensor (CIS) with a pixel-parallel, single-slope analog-to-digital converter (ADC). We adopted a digital bucket relay transfer with multistage flip-flop connection, a pixel unit Cu-Cu connection, and positive-feedback circuitry, to realize a 6.9-μm pixel-pitch, 1.46-Mpixel pixel-parallel ADC. By operating the comparator with a bias current in the subthreshold region of 7.74-111 nA, we succeeded in reducing the peak current during simultaneous ADC. In combination with an ADC standby operation, we succeeded in further reducing the pixel-parallel ADC power consumption. With these techniques, we realized a normalized figure of merit of 0.24 nJ·e-rms/step calculated by dividing the entire sensor power by the effective ADC resolution at a subthreshold current of 111 nA during 660 frames/s operation.