Research On Global Shutter CMOS Image Sensors

Complementary Metal-Oxide Semiconductor(CMOS)image sensor has undoubtedly become the mainstream of digital image acquisition technology with its advanced physical performance.The global shutter CMOS image sensor can avoid the distortion caused by the rolling shutter mode,therefore,it is widely used in the imaging of moving objects,and mainly involving consumer electronics,machine vision,aerospace,military and other fields.In the global shutter pixels,the voltage domain 8T(8 transistors)pixel can not only overcome the problem of low shutter efficiency caused by the charge domain pixels,but also avoid the leakage of the charge in the 7T((7 transistors))pixels.what is more,it can be used to reduce the fixed pattern noise by correlation double sampling operation,so it becomes the mainstream pixel technology of global shutter image sensors.Therefore,this paper designs a global shutter CMOS image sensor based on 8T active pixels.In this paper,the advanced technology of global shutter CMOS image sensor is presented firstly,the working principle and the performance of several different global exposure pixel structures are analyzed.Based on the above analysis,the system framework of a global shutter image sensor is designed.And combined with the requirements of the project,the design specification of each module circuit is determined.Then,the specific circuit design,layout design and device simulation of the pixel module are completed.In addition,the column level readout circuit based on the digital domain correlated double sampling single-slope Analog-to-Digital Converter(ADC)is designed,it is aimed at reducing the column level fixed pattern noise between circuits and increasing the mismatch tolerance in analog circuits.Finally,the design of the digital circuit in the global exposure CMOS image sensor is completed,and the layout of each module is completed finally.SMIC 130nm CMOS technology is used to realize the design of global shutter CMOS image sensor.The chip size of this global shutter CMOS image sensor is6.3mm x 6.4mm,the effective pixel array is 760×480,and the width of the pixe is5um,the conversion gain is 103.2100?V/e~-.The resolution of the single slope ADC is10 bit,and the effective number of bit is 8.95 bits,the ranges of Differential nonlinearity(DNL)and Integral Nonlinearity(INL)are-0.4/0.4LSB and-0.4/0.8LSB,respectively.The frame rate is 73.8 frames per second.