Development of Event-Driven Correlated Double Sampling for A/D Converters in Pixel-Parallel 3-D Integrated CMOS Image Sensors

Abstract

We report novel event-driven noise reduction circuits with correlated double sampling (CDS) technique for pulse-frequency-modulation (PFM) analog-to-digital converters (ADCs). PFM-ADCs are promising for pixel-parallel 3-D integrated image sensors with excellent imaging performance. The developed ADC with CDS consists of comparators, capacitors, and timing control logic circuits that are designed to generate the triggered clocks to cancel kTC noise in a pixel. We confirmed that the prototype ADC showed noise reduction effects and also an excellent linearity with a wide dynamic range of 120 dB, which indicates the feasibility of high-quality pixel-wise image sensors.