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用CMOS(complementary metal oxide semiconductor)图像传感器取代传统医用X射线透视仪器对于医疗设备的便携化、数字化具有重大意义。由于医疗应用的特殊要求,对于CMOS图像传感器要求具有12位以上分辨率的输出,因此本文设计了一个具有14位分辨率的流水线ADC(analog digital converter)来满足X射线CMOS图像传感器系统的要求。由于X射线CMOS图像传感器的面积很大,因此将像素阵列分割成若干块同时并行读出。每一块将用到一个14位的流水线ADC。这种并行结构将大大降低对于ADC速度的要求。根据系统要求,本文设计的ADC的速度为3 MS/s.通过采用类似并行流水线ADC的结构,将ADC设计的速度要求降低一倍,缓解由于高精度设计带来的设计压力。仿真结果表明本设计可以达到14位的设计精度。
The use of CMOS (complementary metal oxide semiconductor) image sensor to replace the traditional medical X-ray fluoroscopy equipment for medical equipment, digitalization is of great significance. Due to the special requirements of medical applications, the CMOS image sensor requires an output with a resolution of 12 bits or more. Therefore, an analog digital converter with 14-bit resolution is designed to meet the requirements of the X-ray CMOS image sensor system. Due to the large area of the X-ray CMOS image sensor, the pixel array is divided into a plurality of blocks and simultaneously read out in parallel. Each block will use a 14-bit pipeline ADC. This parallel structure will greatly reduce the requirements for ADC speed. According to the system requirements, the speed of the ADC designed in this paper is 3 MS / s. By adopting a structure similar to the parallel pipeline ADC, the speed requirement of the ADC design is reduced by one time, easing the design pressure caused by the high-precision design. Simulation results show that the design can achieve 14-bit design accuracy.