A Novel Time-to-Digital Converter Based on Low-Jitter Phase-Locked Loop

ABSTRACTThis paper presents a novel multi-levels time-to-digital converter (TDC) suitable for array architecture for the photon time-of-flight (TOF) measurement. A simple method was applied to solve the initial phase time mismatch caused by random occurrence of the TOF start signal. A low-jitter phase-locked loop (PLL) is adopted to provide excellent clocks to the TDC. The proposed PLL–TDC has a good differential nonlinearity (DNL) (±0.4 LSB) and integral nonlinearity (INL) (±0.5 LSB) due to the low-jitter clock and elimination of initial phase time mismatch. The circuit of the low-jitter PLL was implemented in TSMC 0.35 µm standard complementary metal oxide semiconductor (CMOS) process with 3.3 V supply voltage. The measured result of the low-jitter PLL and the simulated result of the TDC show the proposed 14-bit TDC can realize 1.0 ns time resolution and 16 µs maximum range with 125 MHz centre frequency. Under this given frequency, the time interval error (TIE) jitter is 7.8 ps(rms).