Time-to-digital conversion circuit and method of the same

A time-to-digital conversion circuit, characterized by comprising:

• a first oscillator, activated by a first signal, wherein the first oscillator comprises a plurality of oscillating units having a first delay amount, wherein a first starting end oscillating unit of the plurality of oscillating units in the first oscillator receives the first signal and a first tail end output signal, and a first tail end oscillating unit of the plurality of oscillating units in the first oscillator is configured to generate the first tail end output signal;
• a first counting circuit, coupled to the first oscillator and configured to count a number of times that the first tail end output signal changes, and store the counted number as a first counting result;
• a second counting circuit, coupled to the first oscillator, and configured to count a number of oscillating units with an output change, other than the first tail end oscillating unit, whenever an output of the first starting end oscillating unit changes, and store the number of the oscillating units as a second counting result;
• a second oscillator, coupled to the first oscillator through the first counting circuit and the second counting circuit, wherein the second oscillator is activated by a second signal;
• a first conversion circuit, coupled to the first counting circuit and the second counting circuit and configured to generate a first conversion signal according to the first delay amount and the first counting result and the second counting result stored when the second oscillator is activated, wherein the first conversion signal indicates a first estimated time difference;
• and
• a processing circuit, coupled to the first conversion circuit and configured to generate an output signal at least according to the first conversion signal, wherein the output signal represents a measured time difference between an activation time of the first signal and an activation time of the second signal.