A robust and low-power synchronization technique of coarse-and-fine conversion parts in ring-oscillator-based time-to-digital converters

A novel synchronization technique of coarse-and-fine conversion parts is proposed for low-power ring-oscillator-based time-to-digital converters (TDCs) by using a simple digital circuitry. A ring-oscillator-based TDC architecture, in which a ring oscillator takes fine conversion and a counter does coarse conversion, is suitable for wide-dynamic range measurement applications. However, such TDCs require synchronization between the fine and coarse conversion parts because the D-type flip flop (D-FF) array and the binary counter in the TDC operate asynchronously with each other. In this paper, a novel synchronization technique is proposed, that uses a ring oscillator phase, saving power consumption and chip area compared to previous works. The TDC using the proposed technique is designed and simulated in a 0.18μm 1P6M CMOS process and it achieved 4.66 pJ/conv. energy consumption for logic circuits.