Design Of X-ray Detector Pixel Circuit And Energy Readout Circuit

X-ray detectors can be used in deep space exploration and high-energy physics experiments due to their high photon energy,strong penetrability and strong anti-interference capability.With the expansion of the application field of X-ray detectors and the increasing complexity of the application environ ment,the research on readout circuits of X-ray detectors is also ongoing.In this paper,the pixel circuit in X-ray detector and the readout circuit reflecting its energy amplitude information are studied.Based on the Hua hong hong li 0.13μm process,the overall circuit layout is designed.The pixel array is 40×50,the pixel circuit layout size is 80μm×80μm,and the power consumption is 22.2μW in typical cases.The pixel circuit mainly includes charge sensitive amplifier(CSA),voltage comparator,peak hold circuit,etc.CSA converts the input charge signal into voltage signal and amplifies,and outputs X-ray hit time pulse information and energy amplitude information through voltage comparator and peak holding circuit respectively.In order to debug the pixel circuit,5-bit current steering digital-to-analog converter(DAC)and an R-2R resistor network DAC provide stable bias voltage and current for the whole circuit.The total output range of the current steering DAC is 0～3.2μA,and the step size is 99.89 n A.The total output range of voltage DAC is 0～1.44 V,in which 7-bit voltage DAC provides CSA reset voltage with step size of 11.14 m V.The 8-bit voltage DAC provides a voltage comparator threshold with an step size of 5.59 m V.The analog voltage reflecting the energy amplitude output by pixel circuit is amplified by the output buffer circuit shared by pixel array under the control of the row and column selector switch.The output buffer circuit is realized by a switched capacitor amplifier with configurable gain,and the working clock frequency is 5MHz.When the parasitic capacitance of the sensitive node is controlled at 50 f F and the injected charge number is 2740,the equivalent charge noise of CSA is within 36e-and the gain of CSA is 0.13 m V/e-.The "time shift" of the leading edge of the time pulse signal is controlled within 16 ns,thus realizing time discrimination.When the charge injected into the sensitive node ranges from 137 to 2740,the pixel circuit of X-ray detector and the readout circuit reflecting its energy amplitude information realize the analog output reflecting the energy amplitude of X-ray.