Design Of Low Noise X-ray Pxiel Unit Readout Circuit

The X-ray detector system is a device that converts X-ray energy into digital signal images.It is currently widely used in security inspections,medical systems,aerospace and industrial control and other fields.The X-ray readout circuit is the core part of the entire detector system.It first amplifies and reduces the noise of the output signal of the previous detector into an analog signal,and then digitizes this signal through an analog-to-digital converter.Nowadays,the performance requirements of X-ray readout circuits are getting higher and higher,and high imaging quality,high refresh rate,and wide input detection range have become a common development trend.In order to meet the special performance requirements of the X-ray readout circuit,this paper designs the core pixel unit module in the integral X-ray readout circuit,which specifically includes the Capacitance Trans Impendence Amplifier(CTIA)module,and the Correlated Double Sampling(CDS)module and Successive Approximation Register(SAR)ADC module.Among them,the CTIA module integrates and amplifies the weak charge signal and converts it into a voltage signal that can be detected.The CTIA module of this design can achieve ultra-high conversion linearity of the detection signal at a working speed of 100 k Hz refresh rate,and the addition of the integral capacitor adaptive function can greatly improve the detection range of the input signal;the CDS module can be used to eliminate pixel-level deviation,reduce the noise of the readout circuit,and improve the signal-to-noise ratio of the output signal.The CDS module of this design can reduce the noise equivalent output integrated noise from 36.4μV to 18.9μV without changing the linearity of the output signal;the function of the SAR ADC module is to quantify the analog signal of the front-end circuit and convert it into digital Output code.In the pixel-level readout circuit,the ADC requires small area and low power consumption.The designed 10 bit 100k S/s SAR ADC consumes about 10μW and has an area of only 95μm×60μm,which meets the system requirements.The three modules in the pixel unit work together to convert the weak charge signal of the detector into a digital signal that is not susceptible to interference.Based on the 130 nm 1P8M CMOS process,this paper carries out circuit design,layout design and simulation verification for the CTIA,CDS and SAR ADC modules in the pixel unit.The designed readout circuit pixel unit is powered by 3.3V power supply,the working frame frequency can reach 100 k Hz,the linearity can reach 99.9%,the output voltage swing exceeds 1.5V,and the total power consumption is only 122μW.Within 150μm×150μm.The performance of each circuit module of the pixel unit can meet the application requirements of the X-ray readout circuit.