5.4 A 76mW 500fps VGA CMOS Image Sensor with Time-Stretched Single-Slope ADCs Achieving 1.95e- Random Noise

The demand for high-frame-rate CMOS image sensors is steadily increasing. Column-parallel single-slope (SS) ADCs are widely used in CMOS image sensors, because they can be implemented with small area, low noise, and high energy efficiency. To achieve high frame rate and low noise simultaneously, several techniques using SS ADCs, such as parallel multiple sampling [1], [2], dual-gain slopes [3], and dual-gain amplifiers [4], have been investigated. However, since the clock frequency of the SS ADC is already in the GHz range, it is very challenging to maintain energy efficiency as the frame rate increases further.