Circuit to recover a clock signal from multiple wire data signals that changes state every state cycle and is immune to data inter-lane skew as well as data state transition glitches

• US 9,363,071 B2
• Filed: 03/06/2014
• Issued: 06/07/2016
• Est. Priority Date: 03/07/2013
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Sengoku, Shoichiro, Lee, Chulkyu, Wiley, George Alan, Cheung, Joseph
• Primary Examiner(s): Dsouza, Adolf
• Application Number:
  US14/199,322
• Publication Number:
  US 20140254733A1
• Time in Patent Office: 824 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H03K 5/1252 Suppression or limitation of noise or interference specially adapted for transmission systems H04B15/00, H04L25/08
• CPC Class Codes: H03K 5/1534 Transition or edge detectors
• CPC Class Codes: H04L 25/0272 Arrangements for coupling to multiple lines, e.g. for differential transmission
• CPC Class Codes: H04L 25/14 Channel dividing arrangements , i.e. in which a single bit stream is divided between several baseband channels and reassembled at the receiver
• CPC Class Codes: H04L 25/49 using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems spectral shaping H04L25/03828
• CPC Class Codes: H04L 25/4906 using binary codes
• CPC Class Codes: H04L 25/493 by transition coding, i.e. the time-position or direction of a transition being encoded before transmission
• CPC Class Codes: H04L 7/0066 detection of error based on transmission code rule
• CPC Class Codes: H04L 7/027 extracting the synchronising or clock signal from the received signal spectrum, e.g. by using a resonant or bandpass circuit
• 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 recovery circuit is provided comprising a receiver circuit and a clock extraction circuit. The receiver circuit may be adapted to decode a differentially encoded signal on a plurality of data lines, where at least one data symbol is differentially encoded in state transitions of the differentially encoded signal. The clock extraction circuit may be adapted to obtain a clock signal from state transition signals derived from the state transitions.

Claims

1. A clock recovery circuit, comprising:

a receiver circuit adapted to decode data symbols from signals transmitted on a plurality of data lines, where at least one data symbol is encoded in state transitions of the signals transmitted on the plurality of data lines; and

a clock extraction circuit that obtains a clock signal from state transition signals derived from the state transitions while compensating for skew in different ones of the plurality of data lines, and masking data state transition glitches, wherein the clock extraction circuit uses a feedback delayed instance of a first state transition signal (SDRCLK) to obtain the clock signal.

2. The clock recovery circuit of claim 1, wherein the plurality of data lines is three or more lines.

3. The clock recovery circuit of claim 1, wherein the clock extraction circuit includes

a comparator (804) that compares a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) and outputs a comparison signal (NE);

a set-reset latch (806) that receives the comparison signal (NE) from the comparator (804) and outputs a filtered version of the comparison signal (NEFLT); and

an analog delay device (808) that receives the filtered version of the comparison signal (NEFLT) and outputs the feedback delayed instance of the first state transition signal (SDRCLK), where the feedback delayed instance of the first state transition signal (SDRCLK) is used to obtain the clock signal (DDRCLK).

4. The clock recovery circuit of claim 3, wherein the set-reset latch (810) is reset based on the feedback delayed instance of the first state transition signal (SDRCLK).

5. The clock recovery circuit of claim 3, wherein the clock extraction circuit further includes:

a level latch (810) that receives the first state transition signal (SI) and outputs the level-latched instance of the first state transition signal (S), where the level latch (810) is triggered based on the feedback delayed instance of the first state transition signal (SDRCLK).

6. The clock recovery circuit of claim 1, wherein the clock extraction circuit includes

a comparator (904) that compares a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) and outputs a comparison signal (NE);

a set-reset latch (906) that receives the comparison signal (NE) from the comparator (904) and outputs a filtered version of the comparison signal (NEFLT);

a first analog delay device (902) that receives the filtered version of the comparison signal (NEFLT) and outputs a delayed instance of the filtered version of the comparison signal (NEDEL);

one-shot logic (902/903) that receives the filtered version of the comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) and outputs a second filtered version of the comparison signal (NE1SHOT); and

a second analog delay device (908) that receives the second filtered version of the comparison signal (NE1SHOT) and outputs a feedback delayed instance of the first state transition signal (SDRCLK), where the feedback delayed instance of the first state transition signal (SDRCLK) is used to obtain the clock signal (DDRCLK).

7. The clock recovery circuit of claim 6, wherein the set-reset latch (906) is reset based on the feedback delayed instance of the first state transition signal (SDRCLK).

8. The clock recovery circuit of claim 6, wherein the clock extraction circuit further includes:

a level latch (910) that receives the first state transition signal (SI) and outputs the level-latched instance of the first state transition signal (S), where the level latch (910) is triggered based on the feedback delayed instance of the first state transition signal (SDRCLK).

9. The clock recovery circuit of claim 1, wherein the clock extraction circuit includes

a comparator (1204) that compares a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) and outputs a comparison signal (NE);

a set-reset latch (1206) that receives the comparison signal (NE) from the comparator (1204) and outputs a filtered version of the comparison signal (NEFLT);

a first analog delay device (1202) that receives the filtered version of the comparison signal (NEFLT) and outputs a delayed instance of the filtered version of the comparison signal (NEDEL);

one-shot logic (1202/1203) that receives the filtered version of the comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) and outputs a second filtered version of the comparison signal (NE1SHOT);

a second analog delay device (1208) that receives the second filtered version of the comparison signal (NE1SHOT) and outputs a first delayed instance of the first state transition signal (SDRCLK0), where the first delayed instance of the first state transition signal (SDRCLK0) is used to obtain the clock signal; and

a third analog delay device (1209) that receives the first delayed instance of the first state transition signal (SDRCLK0) and outputs the feedback delayed instance of the first state transition signal (SDRCLK).

10. The clock recovery circuit of claim 9, wherein the set-reset latch (1206) is reset based on the feedback delayed instance of the first state transition signal (SDRCLK).

11. The clock recovery circuit of claim 9, wherein the clock extraction circuit further includes:

a level latch (1210) that receives the first state transition signal (SI) and outputs the level-latched instance of the first state transition signal (S), where the level latch (1210) is triggered based on the feedback delayed instance of the first state transition signal (SDRCLK).

12. The clock recovery circuit of claim 1, wherein the clock extraction circuit includes

a comparator (1304) that compares a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) and outputs a comparison signal (NE);

a set-reset latch (1306) that receives the comparison signal (NE) from the comparator (1304) and outputs a filtered version of the comparison signal (NEFLT);

a first analog delay device (1302) that receives the filtered version of the comparison signal (NEFLT) and outputs a delayed instance of the filtered version of the comparison signal (NEDEL);

one-shot logic (1302/1303) that receives the filtered version of the comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) and outputs a second filtered version of the comparison signal (NE1SHOT);

a second analog delay device (1308) that receives the second filtered version of the comparison signal (NE1SHOT) and outputs a first delayed instance of the first state transition signal (SDRCLK1), where the first delayed instance of the first state transition signal (SDRCLK1) is used to obtain the clock signal;

a third analog delay device (1309) that receives the first delayed instance of the first state transition signal (SDRCLK1) and outputs a second delayed instance of the first state transition signal (SDRCLK2); and

a flip flop (1310) that receives the first state transition signal (SI) and outputs the level-latched instance of the first state transition signal (S), where the level latch (1210) is triggered based on the first delayed instance of the first state transition signal (SDRCLK2).

13. The clock recovery circuit of claim 12, wherein the set-reset latch (1306) is reset based on the second delayed instance of the first state transition signal (SDRCLK2).

14. The clock recovery circuit of claim 1, wherein the signals transmitted on the plurality of data lines comprise a plurality of differentially encoded signals.

15. A method for recovering a clock signal, comprising:

decoding data symbols from signals transmitted on a plurality of data lines, where at least one data symbol is encoded in state transitions of the signals transmitted on the plurality of data lines; and

obtaining a clock signal from state transition signals derived from the state transitions while compensating for skew in different ones of the plurality of data lines, and masking data state transition glitches, wherein the clock signal is a feedback delayed instance of a first state transition signal (SDRCLK) that is used to obtain the clock signal.

16. The method of claim 15, wherein decoding the data symbols comprises:

extracting data from the data symbols.

17. The method of claim 15, wherein the clock signal is obtained by:

comparing a first instance of the first state transition signal (SI) and an instance of the first state transition signal (S) to provide a comparison signal (NE);

filtering the comparison signal (NE) to provide a filtered version of the comparison signal (NEFLT); and

delaying the filtered version of the comparison signal (NEFLT) to provide the feedback delayed instance of the first state transition signal (SDRCLK), where the delayed instance of the first state transition signal (SDRCLK) is used to obtain the clock signal (DDRCLK).

18. The method of claim 15, wherein the clock signal is obtained by:

comparing a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) to provide a comparison signal (NE);

filtering the comparison signal (NE) to provide a filtered version of the comparison signal (NEFLT);

delaying the filtered version of the comparison signal (NEFLT) to provide a delayed instance of the filtered version of the comparison signal (NEDEL);

logically combining the filtered version of the comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) to obtain a second filtered version of the comparison signal (NE1SHOT); and

delaying the second filtered version of the comparison signal (NE1SHOT) to provide the feedback delayed instance of the first state transition signal (SDRCLK), where the delayed instance of the first state transition signal (SDRCLK) is used to generate the clock signal (DDRCLK).

19. The method of claim 15, wherein the clock signal is obtained by:

comparing a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) to provide a comparison signal (NE);

filtering the comparison signal (NE) to provide a filtered version of the comparison signal (NEFLT);

delaying the filtered version of the comparison signal (NEFLT) to provide a delayed instance of the filtered version of the comparison signal (NEDEL);

logically combining the filtered version of the comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) to provide a second filtered version of the comparison signal (NE1SHOT);

delaying the second filtered version of the comparison signal (NE1SHOT) to provide a first delayed instance of the first state transition signal (SDRCLK0), where the first delayed instance of the first state transition signal (SDRCLK0) is used to generate the clock signal; and

delaying the first delayed instance of the first state transition signal (SDRCLK0) to provide the feedback delayed instance of the first state transition signal (SDRCLK).

20. The method of claim 15, wherein the clock signal is obtained by:

comparing a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) to provide a comparison signal (NE);

filtering the comparison signal (NE) to provide a filtered version of the comparison signal (NEFLT);

delaying the filtered version of the comparison signal (NEFLT) to provide a delayed instance of the filtered version of the comparison signal (NEDEL);

logically combining the filtered version of the comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) to provide a second filtered version of the comparison signal (NE1SHOT);

delaying the second filtered version of the comparison signal (NE1SHOT) to provide a first delayed instance of the first state transition signal (SDRCLK1), where the first delayed instance of the first state transition signal (SDRCLK1) is used to generate the clock signal; and

delaying the first delayed instance of the first state transition signal (SDRCLK1) to provide a second delayed instance of the first state transition signal (SDRCLK2),

wherein the level-latched instance of the first state transition signal (S) is obtained from a level latch (1210) that is triggered based on the first delayed instance of the first state transition signal (SDRCLK2).

21. The method of claim 15, wherein the signals transmitted on the plurality of data lines comprise a plurality of differentially encoded signals.

22. A clock recovery circuit, comprising:

means for decoding data symbols from signals transmitted on a plurality of data lines, where at least one data symbol is encoded in state transitions of the signals transmitted on the plurality of data lines; and

means for obtaining a clock signal from state transition signals derived from the state transitions while compensating for skew in different ones of the plurality of data lines, and masking data state transition glitches, wherein the clock signal is a feedback delayed instance of a first state transition signal (SDRCLK) that is used to obtain the clock signal.

23. The clock recovery circuit of claim 22, wherein the means for decoding the data symbols is configured to:

extract data from the data symbols.

24. The clock recovery circuit of claim 22, wherein the signals transmitted on the plurality of data lines comprises a plurality of differentially encoded signals.