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.