Voltage-controlled delay line, direct phase controlled voltage-controlled oscillator, clock/data recovery circuit, and clock/data recovery apparatus

• US 6,166,572 A
• Filed: 03/18/1998
• Issued: 12/26/2000
• Est. Priority Date: 06/13/1997
• Status: Expired due to Fees

• Current Assignee: OKI Electric Industry Company Limited
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Yamaoka, Nobusuke
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Ha, Dac V.
• Application Number:
  US09/040,451
• Time in Patent Office: 1,014 Days
• Field of Search: 375/376, 375/377, 375/371, 375/373, 375/375, 375/327, 375/328, 375/354, 327/270, 327/276, 327/269, 327/271, 327/272, 327/284, 327/299, 327/141, 327/144, 327/146, 327/147, 327/149, 327/150, 327/155, 327/156, 327/153, 327/161, 327/162
• US Class Current: 327/149
• CPC Class Codes: H03K 2005/00026 controlled by an analog electrical signal, e.g. obtained after conversion by a D/A converter
• CPC Class Codes: H03K 5/133 using a chain of active delay devices
• CPC Class Codes: H03L 7/07 using several loops, e.g. for redundant clock signal generation
• CPC Class Codes: H03L 7/0805 the loop being adapted to provide an additional control signal for use outside the loop
• CPC Class Codes: H03L 7/0814 the phase shifting device being digitally controlled
• CPC Class Codes: H03L 7/0995 the oscillator comprising a ring oscillator
• 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/data recovery device employs a phase-locked loop that supplies a single clock signal and a control voltage signal to at least one clock/data recovery circuit. The clock/data recovery circuit has a voltage-controlled delay line or direct phase controlled voltage-controlled oscillator that generates a multiple-phase clock signal, which is used to recover a clock signal and data from a received data signal. The voltage-controlled delay line or direct phase controlled vottage-controlled oscillator has a cascade or ring of voltage controlled logic gates, with propagation delays controlled by the control voltage signal from the phase-locked loop, and additional logic gates that supply the clock signal from the phase-locked loop to a selectable one of the voltage-controlled logic gates.

Claims

1. A voltage-controlled delay line for delaying an externally generated input clock signal according to a control voltage signal and a phase selection signal, comprising:

a first cascaded series of first logic gates with voltage-controlled propagation delays, the propagation delays of said first logic gates being controlled in common by said control voltage signal; and

a plurality of second logic gates receiving said input clock signal, one second logic gate being coupled to every M-th first logic gate in said first cascaded series, M being a positive integer, each of said second logic gates being independently controllable by said phase selection signal, said input clock signal being supplied to one of said first logic gates through one of said second logic gates, as selected by said phase selection signal, and output as a delayed clock signal from a last one of said first logic gates in said first cascaded series.

2. The voltage-controlled delay line of claim 1, wherein said second logic gates also have voltage-controlled propagation delays, further comprising:

a plurality of delay switching circuits providing control voltages to respective second logic gates, responsive to said control voltage signal and a delay switching signal, thereby switching the propagation delays of respective second logic gates between a first value and a second value, said first value being a minimum value, said second value being equal to M times the propagation delays of said first logic gates, transitions between said first value and said second value being made gradually over a certain transient response interval, said delay switching circuits being independently controllable by said delay switching signal.

3. The voltage-controlled delay line of claim 2, further comprising:

a second cascaded series of third logic gates with voltage-controlled propagation delays, a first one of said third logic gates being coupled to the last one of said first logic gates in said first cascaded series, the propagation delays of said third logic gates also being controlled in common by said control voltage signal and being equal to the propagation delays of said first logic gates, said second cascaded series of third logic gates generating from said delayed clock signal a multiple-phase clock signal with all odd number of phases.

4. The voltage-controlled delay line of claim 1, further comprising:

a second cascaded series of third logic gates with voltage-controlled propagation delays, a first one of said third logic gates being coupled to the last, one of said first logic gates in said first cascaded series, the propagation delays of said third logic gates also being controlled in common by said control voltage signal and being equal to the propagation delays of said first logic gates, said second cascaded series of third logic gates generating from said delayed clock signal a multiple-phase clock signal with an odd number of phases.

5. A clock/data recovery circuit for recovering a clock signal and data from a received data signal, comprising:

the voltage-controlled delay line of claim 4;

a data phase monitor coupled to said voltage-controlled delay line, providing a middle phase of the multiple-phase clock signal generated by said voltage-controlled delay line as a recovered clock signal, providing, as recovered data, samples of said received data signal taken at sampling timings determined by said middle phase, comparing transitions of said received data signal with said multiple-phase clock signal, outputting an advance signal when the transitions of said received data signal approach said sampling timings from one direction, and outputting a delay signal when the transitions of said received data signal approach said sampling timings from another direction; and

a controller coupled to said voltage-controlled delay line, for modifying said phase selection signal responsive to said advance signal and said delay signal, thereby shifting said multiple-phase clock signal in phase so that said sampling timings move away from the transitions of said received data signal.

6. The clock/data recovery circuit of claim 5, wherein after modifying said phase selection signal, said controller ignores said advance signal and said delay signal for a certain interval of time.

7. The clock/data recovery circuit of claim 5 wherein, when modifying said phase selection signal from a state in which a first, one of said second logic gates supplies said input clock signal to a state in which a second one of said second logic gates supplies said input clock signal, said controller places said phase selection signal, for one cycle of said input clock signal, in a state in which both said first one of said second logic gates and said second one of said second logic gates supply said input clock signal.

8. The clock/data recovery circuit. of claim 5, wherein said second logic gates also have voltage-controlled propagation delays, and said controller also generates a delay switching signal, further comprising:

a plurality of delay switching circuits providing control voltages to respective second logic gates, responsive to said control voltage signal and said delay switching signal, thereby switching the propagation delays of respective second logic gates between a first value and a second value, said first value being a minimum value, said second value being equal to M times the propagation delays of said first logic gates, transitions between said first value and said second value being made gradually over a certain transient response interval, said delay switching circuits being independently controllable by said delay switching signal.

9. The clock/data recovery circuit of claim 8, wherein:

when said data phase monitor does not output said advance signal and does not output said delay signal, said controller sets said phase selection signal and said delay switching signal so that, if said input clock signal is being supplied through a first one of said second logic gates, said first one of said second logic gates has a propagation delay equal to said first value, and a second one of said second logic gates has a propagation delay equal to said second value;

upon receiving said advance signal, said controller modifies said phase selection signal, thereby causing said input clock signal to be supplied through said second one of said second logic gates, then modifies said delay switching signal, thereby shortening the propagation delay of said second one of said second logic gates from said second value to said first value; and

upon receiving said delay signal, said controller modifies said delay switching signal, thereby lengthening the propagation delay of said first one of said second logic gates from said first value to said second value, waits for said transient response interval, then modifies said phase selection signal, causing said input clock signal to be supplied through a third one of said second logic gates, having a propagation delay equal to said first value.

10. The clock/data recovery circuit of claim 9 wherein:

when modifying said phase selection signal in response to said advance signal, said controller places said phase selection signal, for one cycle of said input clock signal, in a state in which both said first one of said second logic gates and said second one of said second logic gates supply said input clock signal; and

when modifying said phase selection signal in response to said delay signal, said controller places said phase selection signal, for one cycle of said input clock signal, in a state in which both said first one of said second logic gates and said third one of said second logic gates supply said input clock signal.

11. A clock/data recovery apparatus, comprising:

at least one clock/data recovery circuit of the type in claim 5; and

a phase-locked loop coupled to said clock/data recovery circuit, having a loop filter generating said control voltage signal, and a voltage-controlled ring oscillator in which a plurality of fourth logic gates with voltage-controlled propagation delays are coupled in a ring, the propagation delays of said fourth logic gates being controlled by said control voltage signal, said input clock signal being obtained from an output terminal of one of said fourth logic gates.

12. The clock/data recovery apparatus of claim 11, wherein said first logic gates, said third logic gates, and said fourth logic gates are all of identical type.

13. The clock/data recovery apparatus of claim 11, wherein after modifying said phase selection signal, said controller ignores said advance and delay signals for a certain interval of time.

14. The clock/data recovery apparatus of claim 11 wherein, when modifying said phase selection signal from a state in which a first one of said second logic gates supplies said input clock signal to a state in which a second one of said second logic gates supplies said input clock signal, said controller places said phase selection signal, for one cycle of said input clock signal, in a state in which both said first one of said second logic gates and said second one of said second logic gates supply said input clock signal.

15. The clock/data recovery apparatus of claim 11, wherein said second logic gates also have voltage-controlled propagation delays, and said controller also generates a delay switching signal, further comprising:

a plurality of delay switching circuits providing control voltages to respective second logic gates, responsive to said control voltage signal and said delay switching signal, thereby switching the propagation delays of respective second logic gates between a first value and a second value, said first value being a minimum value, said second value being equal to M times the propagation delays of said first logic gates, transitions between said first value and said second value being made gradually over a certain transient response interval, said delay switching circuits being independently controllable by said delay switching signal.

16. The clock/data recovery apparatus of claim 15, wherein:

when said data phase monitor does not, output said advance signal and does not output said delay signal, said controller sets said phase selection signal and said delay switching signal so that, if said input clock signal is being supplied through a first one of said second logic gates, said first one of said second logic gates has a propagation delay equal to said first value, and a second one of said second logic gates has a propagation delay equal to said second value;

upon receiving said advance signal, said controller modifies said phase selection signal, thereby causing said input clock signal to be supplied through said second one of said second logic gates, then modifies said delay switching signal, thereby shortening the propagation delay of said second one of said second logic gates from said second value to said first value; and

upon receiving said delay signal, said controller modifies said delay switching signal, thereby lengthening the propagation delay of said first one of said second logic gates from said first value to said second value, waits for said transient response interval, then modifies said phase selection signal, causing said input clock signal to be supplied through a third one of said second logic gates, having a propagation delay equal to said first value.

17. The clock/data recovery apparatus of claim 16 wherein:

when modifying said phase selection signal in response to said advance signal, said controller places said phase selection signal, for one cycle of said input clock signal, in a state in which both said first one of said second logic gates and said second one or said second logic gates supply said input clock signal; and

when modifying said phase selection signal in response to said delay signal, said controller places said phase selection signal, for one cycle of said input clock signal, in a state in which both said first one of said second logic gates and said third one of said second logic gates supply said input clock signal.

18. A direct phase controlled voltage-controlled oscillator receiving an externally generated input clock signal, a control voltage signal, and a phase selection signal, comprising:

a plurality of first logic gates with voltage-controlled propagation delays, said first logic gates being coupled in a ring, the propagation delays of said first logic gates being controlled in common by said control voltage signal; and

a plurality of second logic gates coupled to respective first logic gates, each of said second logic gates being independently controllable by said phase selection signal, said input clock signal being supplied to one of said first logic gates through one of said second logic gates, as selected by said phase selection signal.

19. The direct phase controlled voltage-controlled oscillator of claim 18, wherein said second logic gates also have voltage-controlled propagation delays, further comprising:

a plurality of delay switching circuits providing control voltages to respective second logic gates, responsive to said control voltage signal and a delay switching signal, thereby switching the propagation delays of respective second logic gates between a first, value and a second value, said first value being a minimum value, said second value being a certain multiple of the propagation delays of said first, logic gates, transitions between said first value and said second value being made gradually over a certain transient response interval, said delay switching circuits being independently controllable by said delay switching signal.

20. A clock/data recovery circuit for recovering a clock signal and data from a received data signal, comprising:

the direct phase controlled voltage-controlled oscillator of claim 18, outputting a multiple-phase clock signal obtained from output terminals of an odd number, greater than one, of said first logic gates;

a data phase monitor coupled to said direct phase controlled voltage-controlled oscillator, providing a middle phase of the multiple-phase clock signal output by said direct phase controlled voltage-controlled oscillator as a recovered clock signal, providing, as recovered data, samples of said received data signal taken at sampling timings determined by said middle phase, comparing transitions of said received data signal with said multiple-phase clock signal, outputting an advance signal when the transitions of said received data signal approach said sampling timings from one direction, and outputting a delay signal when the transitions of said received data signal approach said sampling timings from another direction; and

a controller coupled to said direct phase controlled voltage-controlled oscillator, for modifying said phase selection signal responsive to said advance signal and said delay signal, thereby shifting said multiple-phase clock signal in phase so that said sampling timings move away from the transitions of said received data signal.

21. The clock/data recovery circuit of claim 20, wherein after modifying said phase selection signal, said controller ignores said advance signal and said delay signal for a certain interval of time.

22. The clock/data recovery circuit of claim 20, wherein said second logic gates also have voltage-controlled propagation delays, and said controller also generates a delay switching signal, further comprising:

a plurality of delay switching circuits providing control voltages to respective second logic gates, responsive to said control voltage signal and said delay switching signal, thereby switching the propagation delays of respective second logic gates between a first value and a second value, said first value being a minimum value, said second value being a certain multiple of the propagation delays of said first logic gates, transitions between said first value and said second value being made gradually over a certain transient response interval, said delay switching circuits being independently controllable by said delay switching signal.

23. The clock/data recovery circuit of claim 22, wherein:

when said data phase monitor does not output said advance signal and does not output said delay signal, said controller sets said phase selection signal and said delay switching signal so that, if said input clock signal is being supplied through a first one of said second logic gates, said first one of said second logic gates has a propagation delay equal to said first value, and a second one of said second logic gates has a propagation delay equal to said second value;

upon receiving said advance signal, said controller modifies said phase selection signal, thereby causing said input clock signal to be supplied through said second one of said second logic gates, then modifies said delay switching signal, thereby shortening the propagation delay of said second one of said second logic gates from said second value to said first value; and

upon receiving said delay signal, said controller modifies said delay switching signal, thereby lengthening the propagation delay of said first one of said second logic gates from said first value to said second value, then modifies said phase selection signal, causing said input clock signal to be stippled through a third one of said second logic gates, having a propagation delay equal to said first value.

24. A clock/data recovery apparatus, comprising:

at least one clock/data recovery circuit of the type in claim 20; and

a phase-locked loop having a loop filter generating said control voltage signal, and a voltage-controlled ring oscillator in which a plurality of fourth logic gates with voltage-controlled propagation delays are coupled in a ring, the propagation delays of said fourth logic gates being controlled by said control voltage signal, said input clock signal being obtained from an output terminal of one of said fourth logic gates.

25. The clock/data recovery apparatus of claim 24, wherein said first logic gates, said third logic gates, and said fourth logic gates are all of identical type.

26. The clock/data recovery apparatus of claim 24, further comprising:

a pulse-deleting frequency divider coupled between said phase-locked loop and said clock/data recovery circuit, for reducing said input clock signal in frequency by deleting pulses from said input clock signal, thereby reducing an operating frequency of said controller.

27. The clock/data recovery apparatus of claim 24, wherein after modifying said phase selection signal, said controller ignores said advance signal and said delay signal for a certain interval of time.

28. The clock/data recovery apparatus of claim 24, wherein said second logic gates also have voltage-controlled propagation delays, and said controller also controls generates a delay switching signal, further comprising:

a plurality of delay switching circuits providing control voltages to respective second logic gates, responsive to said control voltage signal and said delay switching signal, thereby switching the propagation delays of respective second logic gates between a first value and a second value, said first value being a minimum value, said second value being a certain multiple of the propagation delays of said first logic gates, transitions between said first value and said second value being made gradually over a certain transient response interval, said delay switching circuits being independently controllable by said delay switching signal.

29. The clock/data recovery apparatus of claim 28, wherein:

when said data phase monitor does not output said advance signal and does not output said delay signal, said controller sets said phase selection signal and said delay switching signal so that, if said input clock signal is being supplied through a first one of said second logic gates, said first one of said second logic gates has a propagation delay equal to said first value, and a second one of said second logic gates has a propagation delay equal to said second value;

upon receiving said advance signal, said controller modifies said phase selection signal, thereby causing said input clock signal to be supplied through said second one of said second logic gates, then modifies said delay switching signal, thereby shortening the propagation delay of said second one of said second logic gates from said second value to said first value; and

upon receiving said delay signal, said controller modifies said delay switching signal, thereby lengthening the propagation delay of said first one of said second logic gates from said first value to said second value, then modifies said phase selection signal, causing said input clock signal to be supplied through a third one of said second logic gates, having a propagation delay equal to said first value.