Clock and data recovery circuit

• US 20040252804A1
• Filed: 06/07/2004
• Published: 12/16/2004
• Est. Priority Date: 06/11/2003
• Status: Active Grant

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Inventors: Aoyama, Morishige
• Granted Patent: US 7,336,754 B2
• Time in Patent Office: Days
• US Class Current: 375/376
• CPC Class Codes: H03D 13/004 the logic means delivering pulses at more than one terminal, e.g. up and down pulses
• CPC Class Codes: H03L 7/0814 the phase shifting device being digitally controlled
• CPC Class Codes: H03L 7/093 using special filtering or amplification characteristics in the loop H03L7/087 - H03L7/091 take precedence
• CPC Class Codes: H04L 7/0025 interpolation of clock signal
• CPC Class Codes: H04L 7/0337 Selecting between two or more discretely delayed clocks or selecting between two or more discretely delayed received code signals

Abstract

A clock and data recovery circuit, for tracking frequency-modulated input data, comprises a phase detector for receiving a data signal and a synchronous clock signal, detecting a phase delay or a phase advance, and outputting an UP1/DOWN1 signal, first and second integrators for integrating the UP1/DOWN1 signal and outputting an UP2/DOWN2 signal and an UP3/DOWN3 signal, respectively, a pattern generator for receiving the UP3/DOWN3 signal from the second integrator to output an UP4/DOWN4 signal, a mixer for receiving the UP2/DOWN2 signal from the first integrator and the UP4/DOWN4 signal from the pattern generator and generating an UP5/DOWN5 signal for output, and a phase interpolator for interpolating the phase of an input clock signal based on the UP5/DOWN5 signal from the mixer, for output are provided. A clock signal output from the interpolator is fed back to the phase detector as the clock.

Claims

1. A clock and data recovery circuit having a frequency tracking loop and a phase tracking loop, said clock and data recovery circuit comprising:

a phase detector comparing a phase of an input data signal with a phase of a synchronous clock signal;

a phase interpolator receiving an input clock signal and a control signal, adjusting a phase of an output clock signal based on the control signal, and supplying the output clock signal to said phase detector as the synchronous clock signal;

said phase detector and said phase interpolator owned in common by said frequency tracking loop and said phase tracking loop;

a pattern generator generating a signal for variably setting the phase of the output clock signal from said phase interpolator based on a result of phase comparison by said phase detector and outputting the so generated signal;

said pattern generator provided in said frequency tracking loop; and

a circuit generating the control signal to said phase interpolator based on a result of phase detection by said phase tracking loop and an output signal of said pattern generator in said frequency tracking loop.

20. The clock and data recovery circuit according to claim 1, wherein said phase detector comprises a circuit performing serial-to-parallel conversation of the result of the phase comparison and then outputting the result of the phase comparison.

24. The clock and data recovery circuit according to claim 1, wherein said phase detector comprises:

a first sampling circuit for sampling the input data signal by the synchronous clock signal;

a second sampling circuit for sampling the input data signal by a complementary signal of the synchronous clock signal;

a third sampling circuit for sampling an output of said first sampling circuit by the synchronous clock signal;

a fourth sampling circuit for sampling an output of said second sampling circuit by the synchronous clock signal;

a first coincidence detection circuit for detecting a coincidence between the output of said first sampling circuit and an output of said fourth sampling circuit; and

a second coincidence detection circuit for detecting a coincidence between an output of said third sampling circuit and the output of said fourth sampling circuit.

28. The clock and data recovery circuit according to claim 24, further comprising:

a first serial-to-parallel conversion circuit for performing serial-to-parallel conversion of an output of said first coincidence detection circuit;

a second serial-to-parallel conversion circuit for performing serial-to-parallel conversion of an output of said second coincidence detection circuit;

a first logic circuit for multiplexing parallel outputs of said first serial-to-parallel conversion circuit into a single output;

a second logic circuit for multiplexing parallel outputs of said second serial-to-parallel conversion circuit into a single output;

a third logic circuit for generating a down signal indicating the result of the phase comparison based on a first output and an inverse signal of a second output of two outputs of said first and second logic circuits; and

a fourth logic circuit for generating an up signal indicating the result of the phase comparison based on an inverse signal of the first output and the second output of the two outputs of said first and second logic circuits.

29. The clock and data recovery circuit according to claim 1, wherein said phase detector comprises:

a first group of sampling circuits for sampling the input data signal by the synchronous clock comprising multi-phase synchronous clocks having mutually different phases;

a second group of sampling circuits for sampling outputs of said first group of sampling circuits by one of the multi-phase synchronous clocks; and

a decoder circuit for receiving a plurality of output signals from said second group of sampling circuits, determining a phase delay or a phase advance of the input data signal with respect to the synchronous clock signal from a change point in values of the plurality of output signals, and outputting an up signal and a down signal.

35. The clock and data recovery circuit according to claim 1, wherein said phase interpolator includes a circuit for performing control such that the phase of the output clock signal is delayed or the phase of the output clock signal is advanced based on the control signal, using a predetermined resolution for a period of the input clock signal as a unit.

39. The clock and data recovery circuit according to claim 35, wherein said phase interpolator receives a spread spectrum clock signal with frequency thereof varied within a predetermined frequency range as the input clock signal.

40. The clock and data recovery circuit according to claim 35, wherein said phase interpolator receives a clock signal of a predetermined fixed frequency is input as the input clock signal.

2. A clock and data recovery circuit comprising:

a phase detector receiving a data signal and a synchronous clock signal and, comparing phases of the synchronous clock signal and the data signal and outputting a result of phase comparison; and

a phase interpolator receiving an input clock signal and a control signal and variably adjusting a phase of an output clock signal;

a pattern generator receiving an integrated value of the result of the phase comparison from said phase detector and generating and outputting a signal for variably setting the phase of the output clock signal of said phase interpolator;

said pattern generator provided in a frequency tracking loop; and

a mixer generating a signal obtained by mixing the integrated value in a phase tracking loop with an output signal of said pattern generator in said frequency tracking loop, said phase tracking loop controlling the phase of the output clock signal from said phase interpolator in accordance with the integrated value of the result of the phase comparison by said phase detector;

the mixer supplying the generated signal to said phase interpolator as the control signal;

the output clock signal from said phase interpolator being fed back to said phase detector as the synchronous clock signal.

3. The clock and data recovery circuit according to claim 2, wherein said phase tracking loop and said frequency tracking loop share an integrator for integrating the result of the phase comparison by said phase detector.

4. The clock and data recovery circuit according to claim 2, wherein when one of said phase tracking loop and said frequency tracking loop is in a stabilized state, said mixer outputs a control signal for adjusting the phase of the output clock signal of said phase interpolator based on the result of the phase comparison by the other loop.

5. The clock and data recovery circuit according to claim 2, wherein said mixer comprises a circuit for outputting a control signal for advancing the phase of the output clock signal of said phase interpolator for predetermined consecutive clock cycles when the result of the phase comparison in said phase tracking loop and the output signal of said pattern generator in said frequency tracking loop both indicate up, and outputting a control signal for delaying the phase of the output clock signal of said phase interpolator for predetermined consecutive clock cycles when the result of the phase comparison in said phase tracking loop and the output signal of said pattern generator in said frequency tracking loop both indicate down.

21. The clock and data recovery circuit according to claim 2, wherein said phase detector comprises a circuit performing serial-to-parallel conversation of the result of the phase comparison and then outputting the result of the phase comparison.

25. The clock and data recovery circuit according to claim 2, wherein said phase detector comprises:

a first sampling circuit for sampling the input data signal by the synchronous clock signal;

a second sampling circuit for sampling the input data signal by a complementary signal of the synchronous clock signal;

a third sampling circuit for sampling an output of said first sampling circuit by the synchronous clock signal;

a fourth sampling circuit for sampling an output of said second sampling circuit by the synchronous clock signal;

a first coincidence detection circuit for detecting a coincidence between the output of said first sampling circuit and an output of said fourth sampling circuit; and

a second coincidence detection circuit for detecting a coincidence between an output of said third sampling circuit and the output of said fourth sampling circuit.

30. The clock and data recovery circuit according to claim 2, wherein said phase detector comprises:

a first group of sampling circuits for sampling the input data signal by the synchronous clock comprising multi-phase synchronous clocks having mutually different phases;

a second group of sampling circuits for sampling outputs of said first group of sampling circuits by one of the multi-phase synchronous clocks; and

a decoder circuit for receiving a plurality of output signals from said second group of sampling circuits, determining a phase delay or a phase advance of the input data signal with respect to the synchronous clock signal from a change point in values of the plurality of output signals, and outputting an up signal and a down signal.

36. The clock and data recovery circuit according to claim 2, wherein said phase interpolator includes a circuit for performing control such that the phase of the output clock signal is delayed or the phase of the output clock signal is advanced based on the control signal, using a predetermined resolution for a period of the input clock signal as a unit.

6. A clock and data recovery circuit comprising:

a phase detector receiving a data signal and a synchronous clock signal, comparing phases of the received two signals to detect a delay and an advance, and outputting a first control signal according to a result of the detection;

a first integrator receiving the first control signal output from said phase detector and integrating the received first control signal to output the resultant signal as a second control signal;

a second integrator receiving the first control signal output from said phase detector and integrating the received first control signal to output the resultant signal as a third control signal;

a pattern generator receiving the third control signal from said second integrator, counting the received third control signal and outputting a fourth control signal based on a result of the counting;

a mixer receiving the second control signal from said first integrator and the fourth control signal from said pattern generator and generating a fifth control signal based on the second control signal and the fourth control signal, for output; and

a phase interpolator receiving an input clock signal and the fifth control signal from said mixer, and adjusting a phase of an output clock signal based on the fifth control signal;

the output clock signal from said phase interpolator being fed back to said phase detector as the synchronous clock.

8. The clock and data recovery circuit according to claim 6, wherein each of the first through fifth control signals includes an up signal indicating an advance in phase and a down signal indicating a delay in phase.

10. The clock and data recovery circuit according to claim 6, wherein said pattern generator comprises:

a first counter receiving the input,clock signal and repetitively counting from zero to a predetermined first count value as a count value;

a second counter receiving the input clock signal and performing counting up and counting down when the third control signal indicates up and down respectively; and

a decoder receiving count outputs from said first counter and said second counter and outputting the fourth control signal based on the count outputs.

12. The clock and data recovery circuit according to claim 10, wherein said decoder includes a circuit for outputting an up signal or a down signal of the fourth control signal at an equal interval or at an interval made close to an equal interval, during a period of cycles corresponding in number to the first count value of said first counter.

14. The clock and data recovery circuit according to claim 10, wherein said decoder receives the count outputs of said first counter and said second counter, decodes the received count outputs and outputs up and down signals as the fourth control signal;

and

said decoder includes a circuit for performing control so as to output the up signal a number of times corresponding to the count value of said second counter during cycles corresponding in number to the first count value of said first counter when the count value of said second counter is positive,

to output the down signal a number of times corresponding to the count value of said second counter during the cycles corresponding in number to the first count value of said first counter when the count value of said second counter is negative, and

not to output the up signal and the down signal during the cycles corresponding in number to the first count value of said first counter when the count value of said second counter is zero.

16. The clock and data recovery circuit according to claim 6, wherein said mixer outputs values of an up signal and,a down signal of the fourth control signal as an up signal and a down signal of the fifth control signal, respectively, when an up signal and a down signal of the second control signal are both inactive or both active;

said mixer outputs values of the up signal and the down signal of the second control signal as the up signal and the down signal of the fifth control signal, respectively, when the up signal and the down signal of the fourth control signal are both inactive or both active;

said mixer activates the up signal of the fifth control signal, for output, for predetermined consecutive clocks when the up signals of the second and fourth control signals are both active; and

said mixer activates the down signal of the fifth control signal for the predetermined consecutive clocks when the down signals of the second and fourth control signals are both active.

17. The clock and data recovery circuit according to claim 16, wherein the mixer outputs the up signal and the down signal of the fifth control signal in inactivated states when the up signal of the second control signal and the down signal of the fourth control signal are both active;

and

the mixer outputs the up signal and the down signal of the fifth control signal in inactivated states when the down signal of the second control signal and the up signal of the fourth control signal are both active.

22. The clock and data recovery circuit according to claim 6, wherein said phase detector comprises a circuit performing serial-to-parallel conversation of the result of the phase comparison and then outputting the result of the phase comparison.

26. The clock and data recovery circuit according to claim 6, wherein said phase detector comprises:

a first sampling circuit for sampling the input data signal by the synchronous clock signal;

a second sampling circuit for sampling the input data signal by a complementary signal of the synchronous clock signal;

a third sampling circuit for sampling an output of said first sampling circuit by the synchronous clock signal;

a fourth sampling circuit for sampling an output of said second sampling circuit by the synchronous clock signal;

a first coincidence detection circuit for detecting a coincidence between the output of said first sampling circuit and an output of said fourth sampling circuit; and

a second coincidence detection circuit for detecting a coincidence between an output of said third sampling circuit and the output of said fourth sampling circuit.

31. The clock and data recovery circuit according to claim 6, wherein said phase detector comprises:

a first group of sampling circuits for sampling the input data signal by the synchronous clock comprising multi-phase synchronous clocks having mutually different phases;

a second group of sampling circuits for sampling outputs of said first group of sampling circuits by one of the multi-phase synchronous clocks; and

a decoder circuit for receiving a plurality of output signals from said second group of sampling circuits, determining a phase delay or a phase advance of the input data signal with respect to the synchronous clock signal from a change point in values of the plurality of output signals, and outputting an up signal and a down signal.

33. The clock and data recovery circuit according to claim 6, wherein said first and second integrators include respective up/down counters for performing counting up or down when a result of phase comparison from said phase detector indicates up or down,

outputting an up signal as the second control signal and the third control signal in response to a next clock when the result of the phase comparison indicates up and a count value thereof is an upper limit value, and initializing the count value, and outputting a down signal as the second control signal and the third control signal in response to the next clock when the result of the phase comparison from said phase detector indicates down and the count value thereof is a lower limit value, and initializing the count value.

37. The clock and data recovery circuit according to claim 6, wherein said phase interpolator includes a circuit for performing control such that the phase of the output clock signal is delayed or the phase of the output clock signal is advanced based on the control signal, using a predetermined resolution for a period of the input clock signal as a unit.

7. A clock and data recovery circuit comprising:

a phase detector receiving a data signal and a synchronous clock signal, comparing phases of the received two signals to detect a delay and an advance, and outputting a first control signal according to a result of the detection;

an integrator receiving the first control signal output from said phase detector and integrating the received first control signal to output the resultant signal as a second control signal;

a pattern generator receiving the second control signal from said integrator, counting the received second control signal and outputting a third control signal based on a result of the counting;

a mixer receiving the second control signal from said integrator and the third control signal from said pattern generator, and generating a fourth control signal based on the second control signal and the third control signal to output the so generated signal; and

a phase interpolator receiving an input clock signal and the fourth control signal from said mixer and then adjusting a phase of an output clock signal based on the fourth control signal;

the output clock signal from said phase interpolator being fed back to said phase detector as the synchronous clock signal.

9. The clock and data recovery circuit according to claim 7, wherein each of the first thorough fourth control signals includes an up signal indicating an advance in phase and a down signal indicating a delay in phase.

11. The clock and data recovery circuit according to claim 7, wherein said pattern generator comprises:

a first counter receiving the input clock signal and repetitively counting from zero to a predetermined first count value as a count value;

a second counter receiving the input clock signal and performing counting up and counting down when the second control signal indicates up and down respectively; and

a decoder receiving count outputs from said first counter and said second counter and outputting the third control signal based on the count outputs.

13. The clock and data recovery circuit according to claim 11, wherein said decoder includes a circuit for outputting an up signal or a down signal of the third control signal at an equal interval or at an interval made close to an equal interval, during a period of cycles corresponding in number to the first count value of said first counter.

15. The clock and data recovery circuit according to claim 11, wherein said decoder receives the count outputs of said first counter and said second counter, decodes the received count outputs and outputs up and down signals as the third control signal;

and

said decoder includes a circuit for performing control so as to output the up signal a number of times corresponding to the count value of said second counter during cycles corresponding in number to the first count value of said first counter when the count value of said second counter is positive,

to output the down signal a number of times corresponding to the count value of said second counter during the cycles corresponding in number to the first count value of said first counter when the count value of said second counter is negative, and

not to output the up signal and the down signal during the cycles corresponding in number to the first count value of said first counter when the count value of said second counter is zero.

18. The clock and data recovery circuit according to claim 7, wherein said mixer outputs values of an up signal and a down signal of the third control signal as an up signal and a down signal of the fourth control signal when an up signal and a down signal of the second control signal are both inactive or both active;

said mixer outputs values of the up signal and the down signal of the second control signal as the up signal and the down signal of the fourth control signal when the up signal and the down signal of the third control signal are both inactive or both active;

said mixer activates the up signal of the fourth control signal, for output for predetermined consecutive clocks when the up signals of the second and third control signals are both active; and

said mixer activates the down signal of the fourth control signal, for output for the predetermined consecutive clocks when the down signals of the second and third control signals are both active.

19. The clock and data recovery circuit according to claim 18, wherein the mixer outputs the up signal and the down signal of the fourth control signal in inactivated states when the up signal of the second control signal and the down signal of the third control signal are both active;

and

the mixer outputs the up signal and the down signal of the fourth control signal in inactivated states when the down signal of the second control signal and the up signal of the third control signal are both active.

23. The clock and data recovery circuit according to claim 7, wherein said phase detector comprises a circuit performing serial-to-parallel conversation of the result of the phase comparison and then outputting the result of the phase comparison.

27. The clock and data recovery circuit according to claim 7, wherein said phase detector comprises:

a first sampling circuit for sampling the input data signal by the synchronous clock signal;

a second sampling circuit for sampling the input data signal by a complementary signal of the synchronous clock signal;

a third sampling circuit for sampling an output of said first sampling circuit by the synchronous clock signal;

a fourth sampling circuit for sampling an output of said second sampling circuit by the synchronous clock signal;

a first coincidence detection circuit for detecting a coincidence between the output of said first sampling circuit and an output of said fourth sampling circuit; and

a second coincidence detection circuit for detecting a coincidence between an output of said third sampling circuit and the output of said fourth sampling circuit.

32. The clock and data recovery circuit according to claim 7, wherein said phase detector comprises:

a first group of sampling circuits for sampling the input data signal by the synchronous clock comprising multi-phase synchronous clocks having mutually different phases;

a second group of sampling circuits for sampling outputs of said first group of sampling circuits by one of the multi-phase synchronous clocks; and

a decoder circuit for receiving a plurality of output signals from said second group of sampling circuits, determining a phase delay or a phase advance of the input data signal with respect to the synchronous clock signal from a change point in values of the plurality of output signals, and outputting an up signal and a down signal.

34. The clock and data recovery circuit according to claim 7, wherein said integrator includes an up/down counter for performing counting up or down when a result of phase comparison from said phase detector indicates up or down,

outputting an up signal as the second control signal in response to a next clock when the result of the phase comparison indicates up and a count value thereof is an upper limit value, and initializing the count value, and

outputting a down signal as the second control signal in response to the next clock when the result of the phase comparison from said phase detector indicates down and the count value thereof is a lower limit value, and initializing the count value.

38. The clock and data recovery circuit according to claim 7, wherein said phase interpolator includes a circuit for performing control such that the phase of the output clock signal is delayed or the phase of the output clock signal is advanced based on the control signal, using a predetermined resolution for a period of the input clock signal as a unit.