Data sampling and recover in a phase-locked loop (PLL)

• US 6,041,090 A
• Filed: 11/14/1997
• Issued: 03/21/2000
• Est. Priority Date: 08/09/1995
• Status: Expired due to Term

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: LSI Logic Corporation (Broadcom, Inc.)
• Inventors: Chen, Dao-Long
• Primary Examiner(s): VO, DON NGUYEN
• Application Number:
  US08/962,890
• Time in Patent Office: 858 Days
• Field of Search: 375/371, 375/372, 375/373, 375/374, 375/375, 375/376, 327/147-150, 327/152, 327/156-159, 331/1 A, 331/11, 331/12, 331/25, 331/46, 331/56, 331/57, 331/60, 331/61, 331/152, 331/161, 331/162
• US Class Current: 375/376
• CPC Class Codes: H03L 7/0891 the up-down pulses controlling source and sink current generators, e.g. a charge pump
• CPC Class Codes: H03L 7/091 the phase or frequency detector using a sampling device H03L7/087 takes precedence
• CPC Class Codes: H03L 7/0995 the oscillator comprising a ring oscillator
• 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 circuit for detecting whether a reference clock signal, one of n phase-shifted adjacent clock signals, of a phase-locked loop (PLL) is aligned with incoming data, comprising: a data sampler for sampling bits of the incoming data with each of the adjacent clock signals, wherein a first of the adjacent clock signals clocks bits 0, 0+n, 0+2n, . . . , and a second of the adjacent clock signals clocks bits 1, 1+n, 1+2n, . . . . Also, a PLL circuit for recovering a clock signal from incoming data, comprising: a clock generator for generating an odd number, n, of phase-shifted adjacent clock signals; a data sampler for sampling the incoming data; a first pair of outputs from the sampler, for use in a phase detector (along with a reference clock of the adjacent clock signals and the incoming data), capable of producing an adjustment output. Another characterization is a method for recovering data in a PLL comprising the steps of: generating n phase-shifted adjacent clock signals for sampling bits incoming to the PLL; wherein a first of the adjacent clock signals clocks bits 0, 0+n, 0+2n, . . . , and a second of the adjacent clock signals clocks bits 1, 1+n, 1+2n, . . . . Similarly, a third of the adjacent clock signals can be used to clock bits 2, 2+n, 2+2n, . . . , as well as a fourth and fifth of the adjacent clock signals.

Claims

1. A circuit for detecting whether a reference clock signal, one of n phase-shifted adjacent clock signals, of a phase-locked loop (PLL) is aligned with incoming data, comprising:

a data sampler for sampling bits of the incoming data with each of the adjacent clock signals, wherein a first of the adjacent clock signals clocks said bits 0, 0+n, 0+2n, . . . , and a second of the adjacent clock signals clocks said bits 1, 1+n, 1+2n, . . . , where n is an odd integer.

2. The circuit of claim 1 further comprising a first pair of outputs from said sampler having been produced from two of the adjacent clock signals for use in a first phase detector along with the reference clock signal and the incoming data.

3. A circuit for detecting whether a reference clock signal, one of n phase-shifted adjacent clock signals, of a phase-locked loop (PLL) is aligned with incoming data, comprising:

a data sampler for sampling bits of the incoming data with each of the adjacent clock signals, wherein a first of the adjacent clock signals clocks said bits 0, 0+n, 0+2n, . . . , and a second of the adjacent clock signals clocks said bits 1, 1+n, 1+2n, . . . ; and

a first pair of outputs from said sampler having been produced from two of the adjacent clock signals for use in a first phase detector.

4. The circuit of claim 3 wherein said first phase detector is capable of producing a phase adjustment output for a charge pump connected in series with a clock generator having generated the adjacent clock signals to operate at a trimmed frequency close to 1/n times the incoming data frequency.

5. A circuit for detecting whether a reference clock signal, one of n phase-shifted adjacent clock signals, of a phase-locked loop (PLL) is aligned with incoming data, comprising:

a data sampler for sampling bits of the incoming data with each of the adjacent clock signals, wherein a first of the adjacent clock signals clocks said bits 0, 0+n;

0+2n, . . . , and a second of the adjacent clock signals clocks said bits 1, 1+n, 1+2n, . . . , wherein a pair of the adjacent clock signals, one of which is the reference clock, is used in a first phase detector; and

said first phase detector further comprises a logic-AND device for operating on a first pair of outputs from said sampler, one of which having been inverted, and a first latch for sampling the reference clock with the incoming data.

6. The circuit of claim 5 wherein said first phase detector further comprises:

first and second flip-flops, each of which operates with an output of said logic-AND device, an output of said first latch, and the other of said pair of adjacent clock signals; and

second and third latches, each for sampling an output of each said flip-flop with the reference clock;

said second and third latches for producing a phase adjustment output.

7. A circuit for detecting whether a reference clock signal, one of n phase-shifted adjacent clock signals, of a phase-locked loop (PLL) is aligned with incoming data, comprising:

a data sampler for sampling bits of the incoming data with each of the adjacent clock signals, wherein a first of the adjacent clock signals clocks said bits 0, 0+n, 0+2n, . . . , and a second of the adjacent clock signals clocks said bits 1, l+n, 1+2n, . . . , wherein a phase adjustment output of the circuit is for a current-type charge pump connected in series with a loop filter and an n-stage voltage-controlled oscillator (VCO) having generated the adjacent clock signals; and

a second phase detector in series with a second charge pump, both of which are connected in parallel with a first phase detector and said current-type charge pump, wherein a second pair of outputs from said sampler, at least one of said second pair different from said first pair of outputs, is used in said second phase detector along with a second reference clock signal of the adjacent clock signals and the incoming data.

8. A circuit for detecting whether a reference clock signal, one of n phase-shifted adjacent clock signals, of a phase-locked loop (PLL) is aligned with incoming data, comprising:

a data sampler for sampling bits of the incoming data with each of the adjacent clock signals, wherein a first of the adjacent clock signals clocks said bits 0, 0+n, 0+2n, . . . , and a second of the adjacent clock signals clocks said bits 1, 1+n, 1+2n, . . . , wherein;

a phase adjustment output of the circuit is for a charge pump connected in series with an n=5-stage voltage-controlled oscillator (VCO) having generated the adjacent clock signals; and

a third of the adjacent clock signals clocks said bits 2, 2+n, 2+2n, . . . , a fourth of the adjacent clock signals clocks said bits 3, 3+n, 3+2n, . . . , and a fifth of the adjacent clock signals clocks said bits 4, 4+n, 4+2n, . . . .

9. The circuit of claim 8:

wherein said charge pump is a voltage-type charge pump connected in series with a low-pass loop filter and said VCO; and

further comprising a first pair of outputs from said sampler for use in a first phase detector along with the reference clock signal and the incoming data.

10. A phase-locked loop (PLL) circuit for recovering a clock signal from incoming data, comprising:

a clock generator for generating an odd number, n, of phase-shifted adjacent clock signals;

a data sampler for sampling the incoming data; and

a first pair of outputs from said sampler for use in a first phase detector along with a reference clock of said adjacent clock signals and the incoming data, said phase detector capable of producing an adjustment output for said clock generator.

11. The PLL circuit of claim 10 wherein:

said clock generator is an n-stage voltage-controlled oscillator (VCO) having generated said adjacent clock signals to operate at a trimmed frequency close to 1/n times the incoming data frequency; and

said first phase detector further comprises a logic-AND device for operating on said first pair of outputs, one of which having been inverted, and a first latch for sampling said reference clock with the incoming data.

12. The PLL circuit of claim 10 wherein:

a frequency detector has sufficiently locked-in the PLL circuit to the frequency of said reference clock;

said clock generator is an n-stage voltage-controlled oscillator (VCO);

a first of said adjacent clock signals clocks said bits 0, 0+n, 0+2n, . . . , a second of said adjacent clock signals clocks said bits 1, 1+n, 1+2n, . . . , and a third of said adjacent clock signals clocks said bits 2, 2+n, 2+2n, . . . .

13. The PLL circuit of claim 10 wherein:

said clock generator is an n-stage voltage-controlled oscillator (VCO);

said data sampler comprises n latches; and

said first phase detector further comprises;

a logic-AND device for operating on said first pair of outputs, one of which having been inverted;

a first latch for sampling said reference clock with the incoming data; and

first and second flip-flops, each of which operates with an output of said logic-AND device, an output of said first latch, and another of said adjacent clock signals.

14. A method for recovering data in a phase-locked loop (PLL) comprising the steps of:

generating n phase-shifted adjacent clock signals for sampling bits incoming to the PLL;

wherein a first of said adjacent clock signals clocks said bits 0, 0+n, 0+2n, . . . , and a second of said adjacent clock signals clocks said bits 1, 1+n, 1+2n, wherein n is an odd number.

15. The method of claim 14 further comprising the step of using a third of said adjacent clock signals to clock said bits 2, 2+n, 2+2n, . . . .

16. The method of claim 15 further comprising the steps of:

said step of generating comprises using an n-stage voltage-controlled oscillator (VCO) operating at a trimmed frequency close to 1/n times the frequency of said bits;

using a fourth of said clock signals to clock said bits 3, 3+n, 3+2n, . . . , and using a fifth of said clock signals to clock said bits 4, 4+n, 4+2n, . . . ;

detecting whether a reference clock of said adjacent clock signals is aligned with said bits; and

outputting the data from the PLL.

17. The method of claim 14 further comprising the steps of detecting whether a reference clock of said adjacent clock signals is aligned with said bits, and in the event of non-alignment, producing a phase adjustment output to adjust phase of the reference clock.

18. A method for recovering data in a phase-locked loop (PLL) comprising the steps of:

generating n phase-shifted adjacent clock signals for sampling bits incoming to the PLL;

wherein a first of said adjacent clock signals clocks said bits 0, 0+n, 0+2n, and a second of said adjacent clock signals clocks said bits 1, 1+n, 1+2n, . . . , wherein n is an odd number, said step of generating comprises using an n-stage voltage-controlled oscillator (VCO) operating at a trimmed frequency close to 1/n times the frequency of said bits;

using a third of said adjacent clock signals to clock said bits 2, 2+n, 2+2n, . . . ;

using a fourth of said clock signals to clock said bits 3, 3+n, 3+2n, . . . , and using a fifth of said clock signals to clock said bits 4, 4+n, 4+2n, . . . ;

detecting whether a reference clock of said adjacent clock signals is aligned with said bits, wherein said step of detecting further comprises the steps of;

operating, using a logic-AND device, on a first pair of said sampled outputs, one of which having first been inverted;

sampling said reference clock with said bits for input into each of a first and second flip-flop; and

sampling an output of each of said first and second flip-flops with said reference clock to produce any requisite phase adjustment output; and

outputting the data from the PLL.

19. A method for recovering data in a phase-locked loop (PLL) comprising the steps of:

generating n phase-shifted adjacent clock signals for sampling bits incoming to the PLL;

wherein a first of said adjacent clock signals clocks said bits 0, 0+n, 0+2n, . . . , and a second of said adjacent clock signals clocks said bits 1, 1+n, 1+2n, . . . ;

detecting whether a reference clock of said adjacent clock signals is aligned with said bits, and in the event of non-alignment, producing a phase adjustment output to adjust phase of the reference clock, wherein said step of detecting further comprises the steps of using a first pair of said sampled outputs, a reference clock of said adjacent clock signals, and said bits to produce said phase adjustment output; and

making any requisite phase adjustments to the PLL.

20. The method of claim 19 further comprising the step of detecting whether a second reference clock of said adjacent clock signals is aligned with said bits, and in the event of non-alignment, producing a second phase adjustment output to make any second requisite phase adjustment to the PLL.

21. A circuit for detecting whether a reference clock signal, one of n phase-shifted adjacent clock signals, of a phase-locked loop (PLL) is aligned with incoming data, comprising:

a first pair of clocked outputs from a data sampler for use in a first phase detector along with the reference clock signal; and

a second pair of clocked outputs from said sampler, at least one of said second pair different from said first pair, used in a second phase detector along with a second reference clock signal of the adjacent clock signals.

22. The circuit of claim 21 wherein:

said first phase detector is capable of producing a first phase adjustment output for a first charge pump in series therewith;

said second phase detector is capable of producing a second phase adjustment output for a second charge pump in series therewith; and

said phase adjustment outputs are for a clock generator of the adjacent clock signals.

23. The circuit of claim 21 wherein said first phase detector further comprises a logic-AND device for operating on said first pair of clocked outputs, one of which having been inverted, and a first latch for sampling the reference clock with the incoming data.

24. The circuit of claim 21 further comprising a third pair of clocked outputs from said sampler, at least one of said third pair different from said second pair, is used in a third phase detector along with a third reference clock signal of the adjacent clock signals and the incoming data.

25. The circuit of claim 24 wherein said third phase detector is capable of producing a third phase adjustment output for a third charge pump in series with a clock generator;

said first, second, and third phase detectors connected in parallel.