Time-to-digital converter apparatus and converting method thereof

A time-to-digital converter apparatus converting a time difference between a start signal and a stop signal being received into a digital code signal, the time-to-digital converter apparatus comprising:

• a first ring oscillator circuit receiving the start signal, the first ring oscillator circuit comprising N first delay stages, where N is an odd number greater than 1;
• a first counter circuit coupled with the first ring oscillator circuit, counting an output signal of the first ring oscillator circuit to generate a first digital code, and stopping counting the output signal of the first ring oscillator circuit according to the stop signal;
• a second ring oscillator circuit receiving the stop signal, the second ring oscillator circuit comprising N second delay stages;
• a second counter circuit coupled with the second ring oscillator circuit, and counting an output signal of the second ring oscillator circuit to generate a second digital code;
• an arbiter circuit coupled with the first ring oscillator circuit and the second ring oscillator circuit, and generating a plurality of arbitration signals according to an output of each of the first delay stages and an output of each of the second delay stages, wherein the arbitration signals indicate a transition state of each of the outputs of the first delay stages and the outputs of the second delay stages;
• and
• a coding circuit coupled with the arbiter circuit and the second counter circuit, and outputting a counting stop signal and a third digital code according to the arbitration signals, wherein the counting stop signal is used to control the second counter circuit to stop counting, and the third digital code indicates a time point of phase coincidence between one of the outputs of the first delay stages and one of the outputs of the second delay stages.