Digital Domain Accumulation Readout Circuit Design Of TDI CMOS Image Sensor

Time-Delay Integration (TDI) image sensor is a special kind of image sensor, aline of CMOS pixel the sensor can expose multiple times along the same object andaccumulate the multiple exposure results together. Compare with the tronditionalmethed of image sensor, higher performance photo can be produced by TDI imagesensor, which will degenerate the signal to noise ration (SNR) of the sensor, so theTDI image sensor is widely used in space imaging, medical imaging and industrialmonitoring. This paper analysis and modeling128stages TDI CMOS image sensor，and pay much attention on analog to digital convert of readout circuit.In this paper, the key technology in the readout circuit of deep sub-micronCMOS-TDI line image sensor is sloved. It discusses the method of signalaccumulating and the architecture of readout circuit in TDI image sensor. The keyblocks of digital domain accumulation of TDI are designed, including doublesampling circuit (CDS), Cyclic ADC and digital domain accumulating circuit. Thispaper focuses on the working way of RSD Cyclic ADC and circuit structure in eachblock. Due to the influence of the process conditions, devices in the circuit will bemismatch. In order to reduce the influence of capacitance mismatch in ADC, thispaper presents a capacitor mismatch insensitive Cyclic ADC. With the structureoptimization, the signal in MDAC will multiply by two without capacitor mismatcheffect. At the last part of the paper, capacitor-reused technique of Cyclic ADC isproposed. With this technique, the ADC converts the data simultaneously with thesampling， which achieves twice speed of the conventional cyclic ADC. Thesimulation shows that with0.18μm CMOS process and a1.8V supply, the total powerconsumption is1.34mW when it operates at4MS/s.