An FPGA-Based High Precision Pulse Width Measurement Time-to-Digital Converter with Dual-TDL Multiplexer Encoder

High precision Time-to-Digital Converters (TDCs) play a pivotal role in contemporary particle physics experiments where the measurement of time-over-threshold (TOT) of signal pulses is essential. The stringent demand for picosecond resolution of pulse widths ranging from several hundred picoseconds to hundreds of nanoseconds, coupled with the high requirements for measurement throughput, presents formidable challenges in the design and optimization of pulse width measurement TDCs. This article introduces a novel dual tapped delay lines (TDL) TDC along with a dual-TDL multiplexer encoder to measure the arrival time and TOT time of signal pulses simultaneously in high precision. Utilizing the aforementioned architecture, a series of dual-TDL TDCs with 2,4,6,8-edge multiple measurements scheme capable of measuring the arrival time and TOT time simultaneously at 250 Msps are implemented in a Xilinx Kintex-7 FPGA. The minimum measurable pulse width is determined by the upper limit speed of the FPGA transmitting port and the characteristics of the high-speed comparator, test as 520 ps in our implementation. With pulse widths ranging from 520 ps to 1000 ns, the average TOT measurement RMS precision of the series TDCs is evaluated to be below 5.5 ps, which can be improved by the increasing times of multiple measurements. Specifically, the 8-edge dual-TDL TDC can achieve a precision as low as 3.4 ps. Furthermore The proposed dual-TDL TDC boasts resource efficiency and cost-effectiveness features, making it well suited for particle physics experiments that demand multi-channel capability at an affordable price, along with high performance.