Clock synchronization device

• US 10,530,563 B2
• Filed: 02/19/2018
• Issued: 01/07/2020
• Est. Priority Date: 06/23/2017
• Status: Active Grant

• Current Assignee: STMicroelectronics Grenoble 2 SAS (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Inventors: Cesar, Etienne
• Primary Examiner(s): Fotakis, Aristocratis
• Application Number:
  US15/898,816
• Publication Number:
  US 20180375637A1
• Time in Patent Office: 687 Days
• CPC Class Codes: H03L 7/0807 concerning mainly a recovery circuit for the reference signal
• CPC Class Codes: H03L 7/085 concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal H03L7/10 takes precedence; circuits for comparing the phase or frequency of two mutually-independent oscillations H03D13/00
• CPC Class Codes: H03L 7/089 the phase or frequency detector generating up-down pulses H03L7/087 takes precedence
• CPC Class Codes: H03L 7/091 the phase or frequency detector using a sampling device H03L7/087 takes precedence
• CPC Class Codes: H03L 7/099 concerning mainly the controlled oscillator of the loop
• 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

In an embodiment, a clock synchronizing circuit includes: a phase comparator including a first circuit having a first input configured to receive a data signal; and a second circuit. The first circuit is configured to detect edges of the data signal. The second circuit includes a clock generator configured to generate a clock signal with adjustable frequency, where the phase comparator is configured to compare, after detecting an edge of the data signal, an edge of the data signal with an edge of the clock signal, and where the second circuit is configured to modify a frequency of the clock signal as a function of an output signal of the phase comparator.

Claims

1. A clock synchronizing circuit comprising:

a phase comparator comprising a first circuit having a first input configured to receive a data signal, the first circuit configured to detect edges of the data signal;

a second circuit comprising a clock generator configured to generate a clock signal with adjustable frequency, wherein the phase comparator is configured to compare, after detecting an edge of the data signal, an edge of the data signal with an edge of the clock signal, and wherein the second circuit is configured to modify a frequency of the clock signal as a function of an output signal of the phase comparator;

a first delay circuit having an input coupled to an output of the clock generator; and

a second delay circuit having an input coupled to the first input of the first circuit, wherein the phase comparator comprises a second flip-flop having a data input and a clock input and a third flip-flop having a data input and a clock input, wherein the data input of each of the second and third flip-flops are coupled to an output of the first circuit, wherein the clock input of the second flip-flop is coupled to an output of the first delay circuit, wherein the clock input of the third flip-flop is coupled to an output of the second delay circuit, and wherein the outputs of the second and third flip-flops are coupled to the second circuit.

2. The circuit of claim 1, wherein the edges of the data signal comprise falling edges.

3. The circuit of claim 1, wherein the first circuit comprises a first flip-flop having a data input coupled to a high-voltage rail and a clock input coupled to a data signal line.

4. The circuit of claim 1, wherein the phase comparator comprises an AND gate having inputs coupled to the outputs of the second and third flip-flops and an output coupled to reset inputs of the second and third flip-flops, the output of the AND gate being further coupled to the first circuit.

5. The circuit of claim 1, wherein the first delay circuit is configured to receive at the input of the first delay circuit the clock signal and to generate at the output of the first delay circuit a delayed clock signal that is delayed by a first duration, and wherein the second delay circuit is configured to receive at the input of the second delay circuit the data signal and to generate at the output of the second delay circuit a delayed data signal that is delayed by a second duration, wherein the first duration comprises a duration between 2% and 50% of a data rate of the data signal and wherein the second duration comprises a duration between 2% and 50% of the data rate of the data signal.

6. The circuit of claim 5, wherein the first duration is equal to the second duration.

7. The circuit of claim 1, wherein the first circuit is configured to detect rising edges of the data signal.

8. The circuit of claim 1, wherein the clock generator comprises a voltage controlled oscillator.

9. The circuit of claim 1, wherein the second circuit comprises a charge pump having an output coupled to the clock generator.

10. The circuit of claim 9, wherein the second circuit further comprises a low-pass filter coupled between the charge pump and the clock generator.

11. The circuit of claim 1, wherein the second circuit comprises a clock divider coupled between an output of the clock generator and an input of the phase comparator.

12. A method of recovering a clock signal associated with a data signal, the method comprising:

generating the clock signal;

receiving the data signal at a clock input of a first flip-flop;

detecting a first edge of the data signal;

after detecting the first edge of the data signal, comparing an edge of the data signal with an edge of the clock signal;

generating an up signal and a down signal based on the comparison by;

receiving an output of the first flip-flop with a data input of a second flip-flop;

receiving the output of the first flip-flop with a data input of a third flip-flop;

receiving a delayed version of the data signal at a clock input of the third flip-flop;

receiving a delayed version of the clock signal at a clock input of the second flip-flop;

generating the up signal with an output of the first flip-flop; and

generating the down signal with an output of the second flip-flop;

adjusting a voltage of a charge pump circuit based on the up and down signals; and

modifying a frequency of the clock signal based on the voltage of the charge pump circuit.

13. The method of claim 12, further comprising generating the data signal and transmitting the data signal.

14. The method of claim 12, further comprising receiving an enable signal at a data input of the first flip-flop.

15. The method of claim 12, wherein modifying the frequency of the clock signal comprises:

when the up signal is higher than the down signal, increasing the frequency of the clock signal; and

when the down signal is higher than the up signal, decreasing the frequency of the clock signal.

16. The method of claim 12, further comprising:

resetting the first, second, and third flip-flops when the up signal is high and the down signal is high.

17. The method of claim 12, wherein a rising edge of the delayed version of the data signal is located between a rising edge of an output of the first flip-flop and a rising edge of the delayed version of the clock signal.

18. The method of claim 12, wherein generating the clock signal comprises:

generating a first clock signal with a clock generator; and

generating the clock signal by dividing the first clock signal by N, wherein N is an integer greater or equal to 1.

19. A circuit comprising:

a clock generator configured to generate a clock signal; and

a phase detector having an output coupled to the clock generator, the phase detector comprising;

a first flip-flop having a clock input configured to receive an asynchronous data signal,

a second flip-flop having a data input coupled to an output of the first flip-flop, and a clock input,

a third flip-flop having a data input coupled to the output of the first flip-flop, and a clock input,

a first delay circuit having an input coupled to an output of the clock generator and an output coupled to the clock input of the second flip-flop,

a second delay circuit having an input coupled to the clock input of the first flip-flop and an output coupled to the clock input of the third flip-flop, wherein the phase detector is configured to;

detect a first edge of the asynchronous data signal,

after detecting the first edge of the asynchronous data signal, compare an edge of the asynchronous data signal with an edge of the clock signal, and

modify a frequency of the clock signal based on the comparison.

20. The circuit of claim 19, wherein the phase detector further comprises an AND gate having inputs coupled to the outputs of the second and third flip-flops and an output coupled to reset inputs of the first, second and third flip-flops.

21. The circuit of claim 19, wherein the first delay circuit is configured to receive at the input of the first delay circuit the clock signal and to generate at the output of the first delay circuit a delayed clock signal that is delayed by a first duration, and wherein the second delay circuit is configured to receive at the input of the second delay circuit the asynchronous data signal and to generate at the output of the second delay circuit a delayed asynchronous data signal that is delayed by a second duration, wherein the first duration comprises a duration between 2% and 50% of a data rate of the asynchronous data signal and wherein the second duration comprises a duration between 2% and 50% of the data rate of the asynchronous data signal.

22. The circuit of claim 21, wherein the first duration is equal to the second duration.