Topmetal-?~- Digital Readout Testing Method Research

With the rapid development of the semiconductor industry, more and more areas began to develop Application Specific Integrated Circuit (ASIC). High-precision,high-resolution pixel detectors are widely used in high-energy physics experiments. Our top-of-the-line TopMetal series of chips developed by the Pixel Detector Laboratory is mainly used to detect the drift over the charge in the medium, resulting in the trajectory of the particle. Topmetal-?- is the first chip in TopMetal series with a complete digital readout function, this thesis deeply studied the test method for Topmetal-?- digital readout.This thesis introduces the structure and working principle of the digital readout channel of the Topmetal-?- chip first. On this basis, the digital readout test platform is introduced, including the design of the test board, the design and simulation of the FPGA control logic, the design of socket software, the design of the script control software and the design of the drawing software. Then, the detailed method and process of quantifying the reference voltage of each pixel by the standard signal excitation of the collected charge, the quantization consistency compensation of the pixel and the digital readout performance of the compensated pixel array are emphasized.The major work of this thesis is summarized as follows:(1) Designed hardware and software test platform, including: design bonding board and test bottom board, FPGA firmware, data transmission software based on TCP/IP,user-oriented control program, data analysis and plotting software. The entire test platform is a automatic testing system. The FPGA firmware interacts with computer software by exchanging byte streams via gigabit ethernet connectio. The firmware module could send data back to the software via ethernet as well.(2) The standard excitation signal source is generated to emulate the charge. According to the characteristic of the electrical signal sensed by TopMetal. The mathematical model is established by using the programmable function signal generator to generate the specific waveform which simulated the collected charges, it is used as the test excitation signal and input to the Gring of each pixel. To simulate the collected charges,in order to achieve TopMetal calibration.(3) The method of pixel consistency compensation is proposed. Firstly, the threshold voltage of each pixel is scanned to obtain the S curve of each pixel threshold voltage distribution S curve, and the characteristics of S curve are analyzed to determine the common voltage and compensation bias for each pixel threshold voltage. And the compensation of the pixel quantization is compensated by setting the threshold voltage compensation value of each pixel. After compensation, the uniformity of the quantization threshold voltage of each pixel after compensation is improved obviously.At the end of this thesis, we test the consistency of pixel array response, verify the pixel consistency compensation test method and get the correct conclusion of Topmetal-?- chip digital read logic function. At the same time, the test results are instructive and meaningful to the design of following TopMetal series chips.