Clock and/or data recovery

• US 7,991,099 B2
• Filed: 04/02/2008
• Issued: 08/02/2011
• Est. Priority Date: 04/02/2008
• Status: Active Grant

• Current Assignee: Lontium Semiconductor Corporation
• Original Assignee: Lontium Semiconductor Corporation
• Inventors: Chen, Feng, Ren, Mingming, Xia, Xianheng, Zuo, Weihua
• Primary Examiner(s): Corrielus; Jean B
• Application Number:
  US12/061,546
• Publication Number:
  US 20090252265A1
• Time in Patent Office: 1,217 Days
• Field of Search: 375/259, 375/340, 375/342, 375/355, 375/371, 327/141
• US Class Current: 375/355
• CPC Class Codes: H03L 7/0814 the phase shifting device being digitally controlled
• CPC Class Codes: H03L 7/091 the phase or frequency detector using a sampling device H03L7/087 takes precedence
• CPC Class Codes: H04L 7/0025 interpolation of clock signal
• 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

Embodiments for clock and/or data recovery may comprise two or more samplers to sample a relatively small number of distinct data sample phase locations of a data pulse relative to an estimate of the location of a center of the data pulse. Signal level values for the sample phase locations may be compared, and sample locations for one or more other data pulses may be adjusted based at least in part on the comparisons.

Claims

1. A method comprising:

sampling a number of data pulses with two samplers at distinct sample locations of the data pulses, the sample locations being relative to an estimate of the location of a center for the data pulses;

comparing, respectively, the signal level values of the sample locations for the number of data pulses; and

adjusting the sample locations for a number of other data pulses based at least in part on the comparisons.

2. The method of claim 1, wherein one of the sample locations comprises a location at the approximate estimate of the location of the center of the data pulses.

3. The method of claim 2, wherein said sampling with two samplers comprises sampling with no more than two samplers.

4. The method of claim 2, further comprising revising the estimate of the location of the center for the number of other data pulses based, at least in part, on the comparisons.

5. The method of claim 1, wherein the sample locations comprise a relatively small number of sample locations.

6. The method of claim 5, wherein the relatively small number of sample locations is used to detect edges of a data eye for the data pulses.

7. The method of claim 6, wherein the sample locations used to detect edges of a data eye for the data pulses comprise four sample locations approximately at −

100°

, at −

80°

, at +80°

, and at +100°

, respectively, relative to the estimate of the center of the data pulses.

8. The method of claim 1, wherein said comparing comprises comparing signal value levels sampled at the sample locations with a signal value level sampled at the estimate of the center of the data pulses.

9. The method of claim 8, wherein said adjusting comprises advancing the sample locations if the comparisons detect that the signal level sampled at a latest sample location is different from that of the signal level sampled at the estimate of the center of the data pulses.

10. The method of claim 8, wherein said adjusting comprises retarding the sample locations if the comparisons detect that the signal level sampled at an earliest sample location is different from that of the signal level sampled at the estimate of the center of the data pulses.

11. A system, comprising:

a transmitting device; and

a receiving device couple to the transmitting device via an interconnect, wherein said receiving device comprises

a first sampler and a second sampler to sample a relatively small number of distinct data sample phase locations of a data pulse received via the interconnect relative to an estimate of the location of a center of the data pulse;

a comparator to compare, respectively, the signal level of the distinct data phase locations for the two samplers for a number of data pulses; and

a controller to adjust the relatively small number of distinct data sample phase locations based at least in part on the comparisons.

12. The system of claim 11, wherein the receiving device comprises a high definition television.

13. A method, comprising:

performing a first plurality of comparisons of data sampled at a first sample point and at a second sample point at a first plurality of phase offsets to determine an approximate data eye center, wherein a phase relationship between the first and second sample points is fixed when determining the approximate data eye center;

fixing the second sample point at the approximate data eye center;

performing a second plurality of comparisons of data sampled at the first sample point at a second plurality of phase offsets to determine a movement of a data edge, wherein the second sample point remains fixed at the approximate data eye center and wherein the phase relationship between the first and second sample points is not fixed when determining the movement of the data edge; and

adjusting the approximate data eye center according to the determined movement of the data edge.

14. An apparatus, comprising:

a first phase interpolator and a second phase interpolator to receive a multi-phase clock from a multi-phase clock generating circuit, the first and second phase interpolators to produce first and second clock signals, respectively;

a first sampler circuit and a second sampler circuit to receive the first and second clock signals, respectively, from the first and second phase interpolators, the first and second sampler circuits further to receive a data signal via a data input line;

a comparator to receive first and second pluralities of sampled data from the first and second sampler circuits, respectively, the comparator to perform a first plurality of comparisons of data sampled at the first and second sample points at a first plurality of phase offsets to determine an approximate data eye center, wherein a phase relationship between the first and second clock signals is fixed when determining the approximate data eye center; and

a controller circuit to fix the second sample point at the approximate data eye center, the controller circuit to deliver timing information to the first and second phase interpolators, the comparator to perform a second plurality of comparisons of data sampled at the first sampler circuit at a second plurality of phase offsets to determine a movement of a data edge, wherein the second sample point remains fixed at the approximate data eye center and wherein the phase relationship between the first and second clock signals is not fixed when determining the movement of the data edge, the controller to adjust the approximate data eye center according to the determined movement of the data edge.

15. A clock and/or data recovery unit, comprising:

only two samplers to sample signal value levels of a data pulse at distinct, respective sample locations;

only two phase interpolators to drive, at least in part, the two samplers; and

a controller to adjust, at least in part, the sample locations for the two samplers, so that one sampler tracks the data pulse transition edge, the other tracks an estimate of the center of the data pulse.