Clock and data recovery circuit

• US 7,715,514 B2
• Filed: 09/08/2005
• Issued: 05/11/2010
• Est. Priority Date: 09/10/2004
• Status: Expired due to Fees

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Inventors: Takeuchi, Masahiro
• Primary Examiner(s): Liu; Shuwang
• Assistant Examiner(s): Perez; James M
• Application Number:
  US11/220,611
• Publication Number:
  US 20060056564A1
• Time in Patent Office: 1,706 Days
• Field of Search: 375/334, 375/354, 375359-362, 375/371, 375373-376, 327/244, 327 47- 48, 327/151, 327160-161, 327/159
• US Class Current: 375/375
• 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 7/0004 Initialisation of the receiver H04L7/0075 and H04L7/10 take precedence
• CPC Class Codes: H04L 7/0025 interpolation of clock signal
• CPC Class Codes: H04L 7/033 using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop

Abstract

A clock and data recovery circuit that tracks the frequency and phase fluctuation of serial data includes a feedback controller for monitoring tracking speed of an extraction clock with respect to the frequency and phase fluctuation of the serial data and applying feedback control to an integrator adaptively and moment to moment, thereby raising the tracking speed of the recovered clock and improving the jitter tolerance characteristic.

Claims

1. A clock and data recovery circuit, receiving input serial data and an input clock signal for recovering a clock signal, said clock and data recovery circuit comprising:

a phase detector, receiving the input serial data and the recovered clock signal as input signals, for comparing phases of the received input signals;

a frequency tracking loop for tracking frequency modulation of the input serial data;

said frequency tracking loop including a first integrator for integrating result of comparison from said phase detector and a pattern generator;

a phase tracking loop for tracking phase fluctuation of the input serial data;

said phase tracking loop including a second integrator for integrating result of comparison from said phase detector; and

a feedback control circuit for feedback-controlling one or both of said first and second integrators;

a phase interpolator, receiving said input clock signal and a control signal and generating the recovered clock signal for output, said phase interpolator variably adjusting the phase of said recovered clock signal;

said phase detector comparing the phase of the input data signal and the phase of the recovered clock signal output from said phase interpolator;

said pattern generator provided in said frequency tracking loop receiving an integrated value of result of phase comparison from said phase detector, for generating and outputting a signal that is for variably setting the phase of the recovered clock signal from said phase interpolator; and

a mixer for generating a signal that is the result of mixing the integrated value in the phase tracking loop, which controls the phase of the recovered clock signal from said phase interpolator in accordance with the integrated value of the result of phase comparison by said phase detector, and the output of said pattern generator in the frequency tracking loop;

wherein the signal generated by said mixer is supplied to said phase interpolator as the control signal;

wherein said first integrator and second integrator are formed by a common integrator shared by said frequency tracking loop and said phase tracking loop, or said first integrator and second integrator separate integrators are provided in said frequency tracking loop and said phase tracking loop respectively; and

wherein said feedback control circuit, monitoring an output from said integrator and variably controlling a parameter of at least one of said integrators based upon result of monitoring, is connected to said common integrator shared by said frequency tracking loop and said phase tracking loop, or is connected to at least one of said first and second integrators provided separately for respective ones of the phase tracking loop and frequency tracking loop.

2. The clock and data recovery circuit according to claim 1, wherein when one loop out of the phase tracking loop and the frequency tracking loop indicates that said one loop is in a stable state, said mixer outputs the control signal, which is for adjusting the phase of the recovered clock signal in said phase interpolator, based upon result of the phase comparison in the other loop.

3. The clock and data recovery circuit according to claim 1, wherein said mixer outputs a control signal, which advances the phase of the recovered clock signal of said phase interpolator, continuously for a prescribed number of clocks if both the result of phase comparison in the frequency tracking loop and the output of said pattern generator in the frequency tracking loop indicate UP, and outputs a control signal, which retards the phase of the recovered clock signal of said phase interpolator, continuously for a prescribed number of clocks if both the result of phase comparison in the phase tracking loop and the output of said pattern generator in the frequency tracking loop indicate DOWN.

4. The clock and data recovery circuit according to claim 1, wherein said integrator comprises a counter, and a parameter of said integrator is number of counts of said counter.

5. The circuit according to claim 4, wherein in a case where said integrator continuously outputs a control signal that retards or advances the phase of one of said two signals input to said phase detector, said feedback controller reduces the number of counts of said counter.

6. The circuit according to claim 4, wherein in a case where said integrator alternately outputs a control signal that retards or advances the phase of one of said two signals input to said phase detector, said feedback controller enlarges the number of counts of said counter.

7. A clock and data recovery circuit, receiving input serial data and an input clock signal for recovering a clock signal, said clock and data recovery circuit comprising:

a phase detector, receiving the input serial data and the recovered clock signal as input signals, for comparing phases of the received input signals;

a frequency tracking loop for tracking frequency modulation of the input serial data;

a phase tracking loop for tracking phase fluctuation of the input serial data, said frequency tracking loop including a pattern generator;

said frequency tracking loop and said phase tracking loop sharing an integrator for integrating result of comparison from said phase detector; and

a feedback control circuit for feedback-controlling said integrator

a phase interpolator, receiving said input clock signal and a control signal and generating the recovered clock signal for output, said phase interpolator variably adjusting the phase of the recovered clock signal;

said phase detector, receiving said input data signal and the recovered clock signal from said phase interpolator as input signals, for comparing phases of the received two input signals, detecting lead or lag and outputting a first control signal in accordance with result of detection;

said integrator, receiving the first control signal output from said phase detector, for integrating the received first control signal and outputting a second control signal;

said pattern generator receiving the second control signal from said integrator, for counting the second control signal, detecting, based upon result of counting, a frequency difference between frequency of the data signal and frequency of the input clock signal to said phase interpolator, and outputting a third control signal; and

a mixer, receiving the second control signal from said integrator and the third control signal from said pattern generator, for generating a fourth control signal based upon the second and third control signals, and supplying the fourth control signal to said phase interpolator as said control signal;

said feedback control circuit monitoring an output of said integrator and variably controlling a parameter of said integrator based upon result of monitoring.

8. The clock and data recovery circuit according to claim 7, wherein said integrator comprises a counter, and a parameter of said integrator is number of counts of said counter.

9. A clock and data recovery circuit, receiving input serial data and an input clock signal for recovering a clock signal, said clock and data recovery circuit comprising:

a phase detector, receiving the input serial data and the recovered clock signal as input signals, for comparing phases of the received input signals;

a frequency tracking loop for tracking frequency modulation of the input serial data;

said frequency tracking loop including a first integrator for integrating result of comparison from said phase detector and a pattern generator;

a phase tracking loop for tracking phase fluctuation of the input serial data;

said phase tracking loop including a second integrator for integrating result of comparison from said phase detector; and

a feedback control circuit for feedback-controlling one or both of said first and second integrators;

a phase interpolator, receiving the input clock signal and a control signal and generating the recovered clock signal for output, said phase interpolator variably adjusting the phase of the recovered clock signal;

said phase detector, receiving the input data signal and the recovered clock signal from said phase interpolator as input signals, for comparing phases of the received two input signals, detecting lead or lag and outputting a first control signal in accordance with result of detection;

said first integrator, receiving the first control signal output from said phase detector, for integrating the received first control signal and outputting a second control signal;

said second integrator, receiving the first control signal output from said phase detector, for integrating the received first control signal and outputting a third control signal;

said pattern generator, receiving the third control signal from said second integrator, for counting the third control signal, detecting, based upon result of counting, a frequency difference between frequency of the data signal and frequency of the input clock signal to said phase interpolator, and outputting a fourth control signal; and

a mixer, receiving the second control signal from said first integrator and the fourth control signal from said pattern generator, for generating a fifth control signal based upon the second and fourth control signals, and supplying the fifth control signal to said phase interpolator as said control signal;

said feedback control circuit monitoring an output of at least one of said first and second interpolators and variably controlling a parameter of said integrator based upon result of monitoring.

10. The clock and data recovery circuit according to claim 9, wherein said integrator comprises a counter, and a parameter of said integrator is number of counts of said counter.