Design Of The Infrared Focal Plane Readout Integrated Circuit With High Dynamic Range

Infrared focal plane detector has the advantages of small size,low power consumption and low cost.As an important part of night vision technology,it attracts much attention in the fields of military,meteorology,and security.In the infrared focal plane imaging system,the readout circuit mainly completes the functions of setting the bias voltage of the infrared detector,signal conversion,sampling and output.The dynamic range of the readout circuit determines the range of radiant energy that the system can correctly sense,which is of great significance to the image quality.With the gradual expansion of the system array,how to design a readout circuit with a wide dynamic range in a limited cell area has become a technical difficulty.Based on the application requirements of the engineering project,this subject has designed a readout circuit with high linearity,large output swing,and high dynamic range in the limited cell area of the 30?m pixel center distance for the working characteristics of the infrared detector.Taking advantage of the high gain characteristics of the sleeve cascode amplifier circuit,a capacitive transimpedance amplifier(CTIA)is constructed as the input stage,which has the characteristics of stable bias voltage and injection efficiency.In order to realize the detection needs of different application environments,the circuit uses two capacitors,including two gain stages with full well charge capacity of400ke-and 5.5Me-,to achieve linear conversion of photocurrent to integrated voltage in different detection environments.The integrated voltage is output to the outside of the pixel through the sample and hold circuit and unity gain buffer.The output buffer adopts a class AB two-stage push-pull operational amplifier,which has the advantages of low power consumption,high loop gain and strong load capacity.This paper completes the circuit design simulation and tape-out verification with TSMC 0.18?m CMOS process.The post-simulation results show that the dynamic range of the readout circuit in high-gain mode and low-gain mode reaches 67.0d B and 75.9d B,the linearity is 99.73% and 99.88%,and the output swings are 3.336 V and 3.466 V,respectively.The area of the unit circuit is 30?m×30?m.The chip is tested with a voltage source and a high-precision resistance analog infrared detector.The test results show that the chip can achieve the basic functions of stable bias voltage,signal conversion and sampling output.The linearity and output swing meet the design index requirements.Due to the limitations of test conditions,parasitic parameters,and environmental interference,the test results of the dynamic range at two gains are 53.9d B and 57.6d B respectively,which is a certain gap with the simulation results.This paper makes a detailed analysis of this,and puts forward feasible suggestions for the subsequent circuit improvement.