Circuit having a clock signal synchronizing device with capability to filter clock-jitter

1. An integrated circuit having a clock signal synchronizing device comprising:

a delay circuit having a variable delay time, the delay circuit configured to delay a compound signal by the variable delay time to provide a delayed clock signal at an output; and

a phase interpolator configured to add an incoming clock signal multiplied with a factor of substantially (1−p) to the delayed clock signal multiplied with a factor of substantially p to generate the compound signal, p being a real number greater than or equal to 0 and smaller than or equal to 1.

2. The integrated circuit of claim 1 , comprising:

a phase interpolator control circuit configured to set the value of p to substantially 0 when the incoming clock signal and the delayed clock signal are not in phase, and sets the value of p to a value greater than 0 and smaller than or equal to 1 when the incoming clock signal and the delayed clock signal are in phase.

3. The integrated circuit of claim 2 , comprising where phase interpolator and phase interpolator control circuit are configured to operate iteratively over a plurality of cycles to average out uncorrelated clock-jitter comprised in the incoming clock signal.

4. The integrated circuit of claim 1 , comprising:

a delay control circuit for controlling the delay circuit to adjust a phase relation between the incoming clock signal and the delayed clock signal.

5. The integrated circuit of claim 4 , further comprising a further delay circuit having a constant delay time and being connected between the output of the delay circuit having the variable delay time and the delay control circuit so that the delayed clock signal is further delayed by the constant time delay.

6. The integrated circuit of claim 4 , comprising wherein the variable delay time of the delay circuit is adjusted by respectively incrementing the variable delay time by a predetermined process until the incoming clock signal and the delayed clock signal fed back from the output of the delay circuit are in phase.

7. The integrated circuit of claim 1 , comprising wherein the incoming clock signal is a differential clock signal.

8. A circuit having a clock signal synchronizing device comprising:

a delay circuit having a variable delay time and delaying compound signal by the variable delay time to output a delayed clock signal;

a delay control circuit for controlling the delay circuit to adjust the phase relation between an incoming clock signal and the delayed clock signal;

a phase interpolator, configured to add the incoming clock signal multiplied with a factor of substantially (1−p) to the delayed clock signal multiplied with a factor of substantially p to output the compound signal to the delay circuit, p being a real number greater than or equal to 0 and smaller than or equal to 1; and

a phase interpolator control circuit, configured to set the value of p to substantially 0 when the incoming clock signal and the delayed clock signal output by the delay circuit are not in phase, and sets the value of p to a value greater than 0 and smaller than or equal to 1 when the incoming clock signal and the delayed clock signal output by the delay circuit are in phase.

9. The circuit of claim 8 , further comprising a further delay circuit having a constant delay time and being connected between an output of the delay circuit having a variable delay time and an input of the delay control circuit.

10. The circuit of claim 8 , comprising wherein the incoming clock signal is a differential clock signal.

11. The circuit of claim 8 , comprising wherein the variable delay time of the delay circuit is adjusted by respectively incrementing the variable delay time by a predetermined process until the incoming clock signal and the delayed clock signal fed back from the output of the delay circuit are in phase, wherein the process is carried out iteratively over a plurality of cycles to average out uncorrelated clock-jitter comprised in the incoming clock signal.

12. The circuit of claim 8 , comprising wherein the variable delay time of the delay circuit is adjusted by respectively decrementing the variable delay time by a predetermined process until the incoming clock signal and the delayed clock signal fed back from the output of the delay circuit are in phase, wherein the processes is carried out iteratively over a plurality of cycles to average out uncorrelated clock-jitter comprised in the incoming clock signal.

13. A device comprising:

a delay circuit having a variable delay time and delaying a compound signal by the variable delay time to output a delayed clock signal;

a delay control circuit for controlling the delay circuit to adjust the phase relation between an incoming clock signal and the delayed clock signal;

a phase interpolator; wherein

the phase interpolator is activated when the incoming clock signal and the delayed clock signal fed back from an output of the delay circuit are substantially in phase and adds the incoming clock signal multiplied with a factor of substantially (1−p) to the delayed clock signal multiplied with a factor of substantially p to output the compound signal to the delay circuit, p being a real number greater than or equal to 0 and smaller than or equal to 1.

14. The device of claim 13 , further comprising a further delay circuit having a constant delay time and being connected between the output of the delay circuit having a variable delay time and an input of the delay control circuit.

15. The device of claim 13 , comprising wherein the incoming clock signal is a differential clock signal.

16. The device of claim 13 , further comprising a phase interpolator control circuit connected to the phase interpolator, the phase interpolator control circuit generating a control signal comprising a value for the factor p being greater than 0 to activate the phase interpolator.

17. A method for operating a circuit having a delay control circuit connected to a delay circuit having a variable delay time, and a phase interpolator, comprising:

receiving an incoming clock signal;

delaying, with the delay circuit, a compound signal to generate a delayed clock signal;

controlling, with the delay control circuit, the variable delay time of the delay circuit to adjust the phase relation between the incoming clock signal and the delayed clock signal; and

when the incoming clock signal and the delayed clock signal fed back from an output of the delay circuit are substantially in phase, adding, with the phase interpolator, the incoming clock signal multiplied with a factor of substantially (1−p) to the delayed clock signal multiplied with a factor of substantially p to output the compound signal, p being a real number greater than or equal to 0 and smaller than or equal to 1.

18. The method of claim 17 , comprising carrying out the controlling and adding iteratively over a plurality of cycles to average out uncorrelated clock-jitter comprised in the incoming clock signal.

19. The method of claim 17 , comprising causing the phase interpolator to operate by a control signal comprising a value for the factor p being greater than 0.

20. The method of claim 17 , comprising adjusting the variable delay time of the delay circuit by respectively incrementing the variable delay time by a predetermined process until the incoming clock signal and the delayed clock signal fed back from the output of the delay circuit are in phase.

21. The method of claim 17 , comprising adjusting the variable delay time of the delay circuit by respectively decrementing the variable delay time by a predetermined process until the incoming clock signal and the delayed clock signal fed back from the output of the delay circuit are in phase.

22. The method of claim 17 , wherein the device comprises an integrated circuit.