Research Of The Timing Control Of The CMOS Image Sensor Based On4T Pixel Structure

In recent years, due to the advantages of compatible production process, low cost and low power consumption, etc., CMOS image sensor has achieved rapid development in many aspects. It is widely used in mobile phones, PC cameras, security monitoring, barcode scanners, toys, car rear view and aerospace and other fields, gradually replacing the CCD image sensor. CMOS image sensor is a chip system, which integrated pixel array, amplifiers, ADC and timing controlling circuits. The timing controlling circuits are an important part of the chip system, providing controlling signals to each module to ensure the correct timing, so as to output a frame image. Therefore, the research of this paper has a very important practical significance. Innovation of this paper is the design of a simplified4T pixel structure. Compared with ordinary4T pixel structure, the simplified structure removes the row select gate within it, thereby increasing the pixel fill factor, simplifying the design of the internal circuit, reducing the area of the layout, and eliminating the random noise caused by the row select gate.The main content of this paper is the timing controlling of the CMOS image sensor with simplified4T pixel structure. Firstly, we analyze the simplified4T pixel structure and the work timing of its readout circuit in detail; secondly, the chip system designs the roll exposure mode on the basis, and analyzes its timing controlling function in depth; finally, focuses on the structure and specific design of each control module within the chip system. Following the top-down design method and the logic functions and timing relationship of all the controlling signals, the design is divided into several sub-modules. Then use the Verilog hardware description language coding them, and finally use the Cadence’s design tools for simulation and verification.After the design is completed, using0.1μm CIS process tapeout. Test result shows that the pixel fill factor of the chip has increased to72%and the sensitivity also has a certain degree of improvement.