Design and Simulation of High Dynamic Range Pixel with Charge Distribution and LOFIC Technology
To solve the problem of insufficient pixel dynamic range,a high dynamic range pixel structure using charge distribution and lateral overflow integrated capacitor(LOFIC)technology is proposed.By splitting LOFIC capacitances and increasing the direct overflow path for a photogenerated charge,the collected overflow charge is distributed between two split capacitors according to the capacitance value during exposure period,and the larger capacitance is dynamically refreshed to realize the compression of high light signal voltage,which enhances the pixel's full-well capacity(FWC)and dynamic range.The adjustment of the number of charge distribution and dynamic refresh and the ratio of capacitance splitting can realize different extensions of dynamic range.In this study,a 6 μm×6 μm pixel is designed based on a 110 nm complementary metal oxide semiconductor process with a high conversion gain(HCG)of 128 μV/e-and an overall LOFIC capacitance of 31.36 fF.Simulation results show that the pixel has a FWC of 1.43 Me-when the capacitance boosting factor is 7,and dynamic range can be up to 116.8 dB.Compared with traditional LOFIC pixel,proposed dynamic range is extended by 16.6 dB.The results indicate that charge distribution LOFIC pixel can achieve higher dynamic range under limited capacitance conditions.
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