电流型图像传感器的低失调电流读出电路  

A low offset current readout circuit for current mode image sensor

作　　者：高点点 虞致国 顾晓峰 GAO Diandian;YU Zhiguo;GU Xiaofeng(Engineering Research Center of IoT Technology Applications(Ministry of Education),Department of Electronic Engineering,Jiangnan University,Wuxi 214122,China)

机构地区：[1]江南大学电子工程系物联网技术应用教育部工程研究中心,江苏无锡214122

出　　处：《微电子学与计算机》2024年第12期85-91,共7页Microelectronics & Computer

基　　金：江苏省重点研发计划产业前瞻与关键核心技术(BE2023019-3)。

摘　　要：电流型图像传感器将光信号转换为电流信号,在读出阶段需要将像素单元偏置成固定电压以保证其处于线性区。针对电流型图像传感器读出电路的钳位电压误差问题,设计了一种基于开关电容的低失调电流读出电路,包含钳位模块、失调修正模块和电流读出模块。钳位模块由运算放大器和反馈管组成,用于将像素单元偏置成固定电压;失调修正模块由电容和开关组成,用于存储并修正钳位模块的失调电压;电流读出模块由电流镜组成,用于将像素单元电流读出至下一级电路。失调修正模块的工作阶段包含失调存储阶段和失调修正阶段,利用相应的开关时序来存储并修正钳位模块的失调电压,减小电流型图像传感器所需钳位电压的误差,提高电流读出精度。采用55 nm CMOS工艺进行设计,结果表明,钳位电压的3σ误差值从5.01 mV降为0.45 mV,电流读出电路的有效位数为11.62位。在1.2 V电源电压下,最大功耗为240μW。单列电流读出电路版图面积为2400μm^(2)。Current mode image sensors convert light signals into current signals,and during the readout phase the pixel cell needs to be biased to a clamping voltage to ensure that it is in the triode region.Aiming at the clamping voltage error in the current mode image sensor readout circuit,a low offset readout circuit based on the switched-capacitor has been proposed,which contains a clamping module,an offset correction module and a current readout module.The clamping module consists of an operational amplifier and a feedback transistor for biasing the pixel cell to a clamping voltage.The offset correction module consists of the capacitor and switch for storing and correcting the offset voltage of the clamping module.The current readout module consists of a current mirror for reading out the pixel cell current to the next level of circuitry.The operating phase of the offset correction module consists of an offset storage phase and an offset correction phase,which utilize the corresponding switching timing to store and correct the offset voltage of the clamping module,reduce the error of the required clamping voltage of the current mode image sensor,and improve the accuracy of the current readout.The circuit is designed in a 55 nm CMOS process.The results show that the 3σerror value of the clamping voltage is reduced from 5.01 mV to 0.45 mV,and the effective number of bits of the current readout circuit is 11.62 bits.At a 1.2 V supply voltage,the maximum power consumption is 240μW.The layout area of the column current readout circuit is 2400μm^(2).

关 键 词：电流型图像传感器 读出电路 钳位电压 开关电容 低失调 

分 类 号：TN432[电子电信—微电子学与固体电子学]