Low‐jitter DLL applied for two‐segment TDC

Abstract

A low-jitter delay-locked loop (DLL) for high-resolution time-to-digital converter (TDC) is proposed in this study. The generated high accurate and low-jitter outputs with uniformly distributed multiphase clocks directly from the voltage-controlled delay line (VCDL) in DLL are applied to two-segment TDC. For reducing the static phase offset in locked state, the charge pump with interior feedback loop is used to achieve a better current matching between the charging and discharging currents. An improved phase detector as well as a differential VCDL excellent in linearity property and noise suppression is utilised for reducing the output clock jitter. Fabricated by TSMC 0.35 μm complementary metal-oxide-semiconductor process, the measurement results show that DLL's frequency locking range is 60-240 MHz, the output clock jitters at 125 MHz are 3.6 ps for root mean square and 35.07 ps for peak-to-peak. By clock period counting and eight-phase discrimination, the resolution of <1 ns and maximum range of around 1 μs as well as the differential non-linearity <0.68 LSB and the integration non-linearity within −0.97 to 1.24 LSB are obtained for two-segment TDC.

Dead-Zone Free, Static Phase Offset Improvement Phase Detector for High Resolution and Low Jitter Delay-Locked Loop

“…This causes the charge pump will charges and discharges simultaneously when the DLL is in locked state. Static phase offset will occur due to the current mismatch of charge pump [4]. So the charge pump requires additional circuitry to improve current matching, which increases design complexity [5,6].…”

Fine resolution delay tuning method to improve the linearity of an unbalanced time‐to‐digital converter on a Xilinx FPGA

“…Time-to-digital converters (TDCs) are used in various engineering applications for fine time intervals measurements. For instance, TDCs are used in positron emission tomography [1], fluorescence lifetime imaging microscopy [2] or to build all digital phase-locked loops [3]. TDCs are also used in some measurement instruments such as oscilloscopes and logic analysers.…”