Phase detecting circuit having adjustable gain curve and method thereof
A phase detecting circuit having an adjustable gain curve includes a plurality of phase detectors and a logic circuit. The phase detectors detect phase differences between a data signal and a plurality of clock signals by comparison to output a plurality of control signals. The clock signals have the same frequency but different phases, and the frequency of the data signal is a multiple of the frequency of the clock signals. The logic circuit performs various logic operations according to these control signals to output at least one set of gain control signals for adjusting a gain curve of the phase detecting circuit.
1. A phase detecting circuit having an adjustable output operation curve, comprising:
a plurality of phase detectors for detecting phase differences between a data signal and a plurality of clock signals by comparison, respectively, to output a plurality of control signals, wherein the clock signals have the same frequency but difference phases, and a frequency of the data signal is a multiple of the frequency of the clock signals; and
a logic circuit comprising at least two AND gates for performing various logic operations according to the control signals to output at least one set of gain control signals for adjusting an output operation curve to generate a dead zone of the phase detecting circuit,
wherein the output operation curve includes at least two step functions, and at least two sets of gain control signals control at least two sets of current sources in a charge pump to generate at least two currents.
2. The phase detecting circuit according to claim 1 , wherein when the number of the clock signals is n, the frequency of the data signal is equal to n/2 times that of the clock signals, and the phase detecting circuit comprises n phase detectors for receiving the n clock signals to output the n control signals.
3. The phase detecting circuit according to claim 1 , wherein each of the phase detectors comprises:
a D flip-flop for receiving the data signal and one of the clock signals to sample the data signal according to an edge of the clock signal; and
an XOR gate, which is coupled with the D flip-flop and a D flip-flop of a previous stage of phase detector, for receiving outputs of the two D flip-flops and outputting one of the control signals.
4. The phase detecting circuit according to claim 1 , wherein the logic circuit comprises:
a plurality of logic gates for performing the logic operations according to the control signals to output a plurality of sets of the gain control signals for respectively controlling a plurality of sets of current sources of a charge pump to adjust different output operation curves.
5. A method of adjusting an output operation curve, the method comprising the steps of:
detecting phase differences between a data signal and a plurality of clock signals by comparison to generate a plurality of control signals, respectively, wherein the clock signals have the same frequency but difference phases, and a frequency of the data signal is a multiple of the frequency of the clock signals; and
performing various logic operations according to the control signals to adjust the output operation curve,
wherein the step of performing the logic operations is to perform AND operations, and the output operation curve includes at least two step functions, and outputting at least two sets gain control signals controlling at least two sets of current sources in a charge pump to generate at least two currents for adjusting different output operation curve to generate a dead zone.
6. The method according to claim 5 , wherein when the number of the clock signals is n, the frequency of the data signal is equal to n/2 times that of the clock signals, and the detecting step outputs the n control signals.
7. The method according to claim 5 , wherein the step of performing the logic operations comprises:
outputting a plurality of sets of gain control signals for respectively controlling a plurality of sets of current sources of a charge pump to adjust different output operation curves.