High Precision Time Digital Converter Based On FPGA

High-precision time-to-digital converters(TDC)based on Field-Programmable Gate Array(FPGA)are widely used in time of fly(TOF)measurement field,such as satellite navigation,medical positron tomography systems,high-energy physics experiments and so on.With the popularity of portable experimental equipment and wearable medical equipment,which require the application of TOF measurement technology in the variable environment,it is becoming more and more important to propose a novel TDC method that can maintain high accuracy in a wide temperature range.This paper presents a non-uniform multiphase(NUMP)TDC implemented in a 60 nm FPGA with real-time temperature correction.When the NUMP TDC is implemented on Intel Cyclone 10 LP series FPGAs,its accuracy decreases sharply with temperature changes.When the temperature rises from 40? to 80?,the timing accuracy deteriorates from 7.2ps to 43.4ps.In view of this,a new online temperature measurement and correction algorithm is proposed.A clock order confirmation algorithm is used to analyze the delay chain's temperature characteristics.By configuring dedicated temperature measurement registers at both ends of the delay chain or adopting a dedicated temperature measurement delay chain,the code density method is used to determine the descendent clocks' phases of the temperature measurement delay units.The variation of relative phase indicates the temperature's change.When the temperature fluctuations exceed a certain threshold,temperature correction is triggered,and the decoding lookup table obtained from the initial order confirmation is corrected.In order to verify the performance of this temperature correction algorithm,a dualchannel NUMP TDC with temperature correction is implemented based on Intel Cyclone10 LP FPGA.An external pulse signal was used to test the NUMP TDC timing performance in the temperature range of 5? to 80?,3.28 ps timing resolution and 8.8ps intrinsic timing precision were finally achieved.Furthermore,some important issues such as resource utilization and power consumption are discussed to lay the foundation for multi-channel expansion and to further realize 32-channel NUMP TDC.An internal pulse signal test was carried out and a precision of 8.3ps was achieved.Among the TDCs implemented by FPGA based on the same processing technology,the NUMP TDC with temperature correction proposed in this article is at the top level in the world.This study shows that NUMP TDC with temperature correction has the advantages of excellent timing precision and temperature stability.The NUMP TDC can support for online temperature correction without temperature sensors and for multi-channel asynchronous correction.It is suitable for temperature-sensitive TOF measurement fields.