A time-to-digital converter (TDC) is disclosed, which comprises a ring oscillator module and a digital error correction module. The ring oscillator module is configured to receive a sampling signal, an addressing signal, and a preset signal, and includes: a ring oscillator arranged with a plurality of inverters; a phase sampler configured to sample phase signals generated by the inverters for generating a first output signal; a counter clock generator configured to generate first and second clock signals; first and second counters configured to respectively generate first and second counter output signals; and a data sampler configured to sample the first and second counter output signals to respectively generate second and third output signals. The digital error correction module is arranged to process the first, second and third output signals for generating a digital signal.