Research On Pixel Array Of Large Area Array Global Shutter CMOS Image Sensor

With the continuous development of CMOS image sensors(CISs)technology,CISs are widely used in various fields.However,the typical rolling shutter CIS has inherent image distortion when shooting high-speed moving objects,and this problem is well solved in the global shutter CIS.Hence,the global shutter CISs have extremely important application value in machine vision,industrial measurement and other fields.Whereas,the design complexity of the global shutter CIS will increase with the expansion of the pixel array,resulting in a series of non-ideal effects.Based on it,this paper studies the structure and working principle of the pixels in the large area array global shutter CIS,and analyzes the design points of the photodetector,floating diffusion node and transfer transistor in the pixel.Then,this paper focuses on the signal attenuation caused by the power supply crosstalk of the row driver circuits in the eight-transistor global shutter CIS.The parallel operation of the row drivers in eight-transistor global shutter CIS can cause a large peak current on the power supply,which would cause power supply crosstalk in the row driver circuit.The power supply crosstalk of row driver circuit would affect the normal operation of the pixels,thus causing the charges stored in the pixel storage node to leak.As a result,the output signal of the CIS would be attenuated.The signal attenuation caused by the power supply crosstalk of the row driver circuit is quantitatively analyzed by establishing the circuit model and the mathematical model,and a separate power supply layout method for the row driver circuit is proposed.This method reduces parasitic resistance and eliminates signal attenuation by introducing additional power supplies to power the susceptible row driver circuit.In this paper,the circuit simulation under different power supply structures is carried out based on the 0.13?m CMOS process and 2000×2 row drive circuit model.The simulation results show that the separate power supply structure can reduce the power supply crosstalk noise from 1.17 V to 2.58?V.Based on the 0.13?m CMOS process,two chips with different row driver circuit power structures are measured.The measurement results show that in the chip with the typical shared power structure,the output signal is limited to about 303ADU(0.059V)due to the existence of power supply crosstalk.The saturated output signal of the chip with a separate power supply structure is 2200 ADU(0.43V),which is in accordance with the theoretical output signal value(2200ADU or 0.43V)when the pixel is saturated.Therefore,the separate power supply structure can effectively eliminate the signal attenuation caused by the power supply crosstalk of the row driving circuit.