Design And Application Of High Precision Time-to-Digital Converter Based On TSMC 0.18?m CMOS Technology

Fluorescence lifetime imaging(FLIM)technology is used to measure the fluorescence lifetime value of samples,and then obtain the physical and chemical characteristics of the sample and its microenvironment.Due to high sensitivity and high reliability,it is widely used in cell biology,cancer diagnosis and blood analysis,et al.As the core circuit module of fluorescence lifetime imaging,the performance of time-to-digital converter(TDC)directly affects the function realization and result of FLIM.However,there still have some problems in the design of TDC such as,time resolution,dynamic range and measurement error.How to break through the compromise between them,and designing a high-performance TDC have very important theoretical and practical significance for FLIM.In this thesis,a two-stage TDC chip was designed based on TSMC 0.18?m CMOS mixed signal process.Based on this TDC,a single photon detection system for FLIM was built.The main contents of this thesis are as follows:1.The basic principle and structure of TDC were analyzed,and a two-stage TDC with both high time resolution and dynamic range was proposed.The second-level high-precision TDC adopts the design idea of reducing the length of a single delay chain and improving the anti-interference ability of the delay unit,thus achieving low measurement error.The simulation results shown that the designed TDC can achieve 30ps time resolution and 241ns dynamic range.The differential nonlinearity and integral nonlinearity are ±0.41LSB and ±0.42LSB respectively,and the offset error is less than 3%.2.Based on two-stage TDC,combined with single photon avalanche diode(SPAD),quenching circuit,storage readout circuit and other modules,a single photon detection system for FLIM was built.The system was realized with both semi-customized and fully-customized methods to ensure the performance and reduce the design difficulty.The simulation results shown that the breakdown voltage of SPAD is about 11.3 V,the dead time of quenching circuit is about 40ns,and the transmission rate of UART is 19200bps.When two fluorescent signals was detected at a clock frequency of 526MHz,the quantization error is restricted within 10ps.3.By using the a priori condition that the occurrence probability of fluorescence signal decreases with time,a TDC with non-uniform delay unit was designed and verified.Theoretical calculations shown that the designed non-uniform TDC has a smaller variance and higher measurement accuracy when reducing the fluorescence lifetime value.The designed single photon detection system for FLIM has some advantages in working frequency,accuracy,test range,measurement error and dead time.Although the proposed TDC with non-uniform delay unit still needs to optimize and improve,it provides a guide for future research.