A High-Time-Resolution Time-to-Digital Converter Using Coupled Ring Oscillator with Phase Averaging

This paper proposes a high-time-resolution time to digital converter (TDC) using a coupled ring oscillator (CRO) with phase averaging. The CRO can generate short time interval multiphase clocks, and combining it with a counter enables a high-time-resolution TDC with a wide input range and relatively small circuitry. In addition, the application of phase averaging to the CRO reduces the timing error due to mismatch. A novel sampling technique is also proposed to eliminate the sampling error due to counter delay and glitches. Post-layout simulations were performed on a 10-bit TDC in 28-nm CMOS technology to evaluate the performance of the proposed TDC. The results showed that the high time resolution of 2.5 ps and low power dissipation of 15.6 m W at the sampling frequency of 350 MHz could be obtained, along with the FOM of 0.083 pJ/conv.-step.