A 2.03-mW CMOS Image Sensor With an Integrated Four-Stacked Charge-Recycling Driver for Image Signal Transmission

• Published in: IEEE access 2022, Vol.10, p.99553-99561
• Main Authors: Kim, Sang-Hoon, Cho, Yongsung, Lee, Jiwon, Chun, Jung-Hoon, Choi, Jaehyuk
• Format: Article
• Language: English
• Subjects: Analog to digital converters; CMOS; CMOS image sensor; CMOS image sensors; correlated-multiple-sampling (CMS); dual-mode; Electric potential; Handwriting; Image transmission; Imaging; Low power electronics; low-power; Phase locked loops; Power consumption; Power demand; power reduction techniques; Random noise; Recycling; Sampling methods; Sensors; Signal to noise ratio; Signal transmission; Transistors; Transmitters; Voltage
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2022.3207298

We propose a CMOS image sensor with a dedicated low-power imaging mode and low-power integrated transmitter. The proposed CMOS image sensor selectively operates in dual mode: a high-quality mode with a 1.5 V supply voltage of readout circuits to achieve a high signal-to-noise ratio (SNR), and a low-power mode with a 0.9 V supply voltage to support always-on imaging. To further reduce the power consumption in the low-power mode, a single-slope analog to digital converter (ADC) embeds a power cutoff scheme in the comparator and a two-step conversion with dual reference voltages. To alleviate the SNR degradation in the low-power mode, which inherently occurs from voltage scaling, a correlated multiple sampling technique that consumes negligible power overhead is implemented using the proposed window-counting scheme. To reduce the significant power consumption that occurs during image signal transmission, an integrated transmitter with four-stacked charge-recycling drivers is used so that four symbols are simultaneously transmitted with a shared supply voltage. A prototype CMOS image sensor with 680 \times 520 pixels is fabricated using 110-nm CMOS image sensor technology. The fabricated CMOS image sensor consumes only 301~\mu \text{W} (at 15 fps) in the sensor core and 2.03 mW including the transmitter and phase locked loop (PLL) while generating low temporal random noise under 0.27 LSB with correlated multiple sampling.