Time-to-digital conversion circuit and time-to-digital converter including the same

1. A time-to-digital conversion circuit for converting a time difference between two input signals to a 1-bit digital value, and adjusting the time difference between the two input signals to generate two output signals, the time-to-digital conversion circuit comprising:

a phase comparator configured to compare phases of the two input signals with each other to generate the digital value;

a phase selector configured to output one of the two input signals which has a leading phase as a first signal, and the other of the two input signals which has a lagging phase as a second signal; and

a delay unit configured to output the first signal with a delay, wherein

the time-to-digital conversion circuit outputs the signal output from the delay unit and the second signal as the two output signals.

2. The time-to-digital conversion circuit of claim 1 , wherein

the phase selector includes a first logic circuit configured to perform a logical AND operation of the two input signals, and a second logic circuit configured to perform a logical OR operation of the two input signals, and outputs any one of output signals from the first and second logic circuits as the first signal and the other of the output signals from the first and second logic circuits as the second signal.

3. The time-to-digital conversion circuit of claim 2 , wherein

the first logic circuit includes a NAND circuit,

the second logic circuit includes a NOR circuit, and

the NAND circuit and the NOR circuit form a symmetric circuit configuration.

4. The time-to-digital conversion circuit of claim 2 , wherein

the phase selector includes a time difference amplifier configured to amplify a time difference between the output signals of the first and second logic circuits to output two signals, and outputs the two signals output from the time difference amplifier as the first and second signals.

5. The time-to-digital conversion circuit of claim 3 , wherein

the phase selector includes a time difference amplifier configured to amplify a time difference between the output signals of the first and second logic circuits to output two signals, and outputs the two signals output from the time difference amplifier as the first and second signals.

6. The time-to-digital conversion circuit of claim 2 , wherein

the phase selector includes a time difference amplifier configured to amplify the time difference between the two input signals to output two signals, and

the first and second logic circuits perform logical operations of the two signals output from the time difference amplifier.

7. The time-to-digital conversion circuit of claim 3 , wherein

the phase selector includes a time difference amplifier configured to amplify the time difference between the two input signals to output two signals, and

the first and second logic circuits perform logical operations of the two signals output from the time difference amplifier.

8. A time-to-digital converter for converting a time difference between two input signals to a digital code, the time-to-digital converter comprising:

the time-to-digital conversion circuit of claim 1 including a plurality of time-to-digital conversion circuits coupled in cascade, wherein

delay times of the delay units in the time-to-digital conversion circuits are set such that the delay time of each delay unit is reduced to a half of the delay time of a directly preceding one of the delay units sequentially from the time-to-digital conversion circuit in a first stage.