Research And Design Of High Precision TDC Based On DLL

Of the seven basic physical quantities of the International System of Units,the quantity of time is the most basic.Its universality,high-precision measurement,and extensiveness are not available in other physical quantities.In order to explore the nature and relationship between certain physical quantities,they are often converted into time quantities for measurement.The TDC can convert the analog time signal into a digital signal that is easy to measure.It can complete the conversion between them and handle the time interval between two asynchronous signals.TDC is used in many fields due to its superior performance and high-precision measurement,such as laser ranging,electronic measurement,medical,and high-energy physics.In the field of high-precision measurement,TDC is often required to achieve ps-level time measurement accuracy,and the research of high-performance TDC is particularly important.In the research on TDC in recent years,the main methods to achieve TDC are:Flash TDC,Vernier TDC and so on.The current TDC structure is mostly a single mode or a two-stage structure.When achieving ps-level accuracy,in order to save area,the dynamic range that can be reached is mostly ns-level.Therefore,achieving high precision and high dynamic range at the same time has been the bottleneck of TDC research and the direction of TDC development.In addition,the stability and accuracy of TDC are also important factors to be considered in the research process.Aiming at the current research bottleneck and development direction of TDC,this paper proposes a circuit architecture of high-precision TDC based on DLL according to the current TDC combination principle.The TDC is a three-level TDC structure,which mainly includes Coarse TDC,Middle TDC,Fine TDC,and DLL circuit.By performing hierarchical measurement of time intervals,the TDC can achieve not only a wide dynamic range,but also high resolution.In this paper,the Coarse TDC uses the counter TDC architecture,which can achieve a wide dynamic range.The Middle TDC adopts the Flash TDC architecture tohandle the residual error of the Coarse TDC.The Fine TDC adopts the Vernier TDC architecture to handle the residual error of the Middle TDC,and can achieve high resolution that breaks through the gate delay limit.In addition,the DLL is used to provide a reference voltage for the Middle TDC and the Fine TDC,which greatly improves the stability and accuracy of the TDC at high frequencies.This design uses SMIC 0.13?m process,and completes circuit design,layout drawing and circuit simulation through software such as Cadence and Matlab.With a640 MHz clock input,the DLL-based high-precision TDC designed in this paper can achieve a dynamic range of 51 ?s,a time rsolution of 10 ps,and a dead time of less than 2 ns.