INTER-PAIR SKEW ADJUSTMENT

• US 20100295591A1
• Filed: 05/20/2009
• Published: 11/25/2010
• Est. Priority Date: 05/20/2009
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Quellan, Inc. (Renesas Electronics Corporation)
• Inventors: Chaahoub, Faouzi, Asmanis, Georgios
• Granted Patent: US 8,429,439 B2
• Time in Patent Office: Days
• US Class Current: 327/276
• CPC Class Codes: H04L 25/0276 Arrangements for coupling common mode signals
• CPC Class Codes: H04L 25/0298 Arrangement for terminating transmission lines
• CPC Class Codes: H04L 25/03878 Line equalisers; line build-out devices

Abstract

A skew adjustor that can reduce inter-pair skew between differential signals received via a cable is disclosed. In one embodiment, a skew adjustor includes: a skew detector that receives signals from a cable, and provides a detected skew amount when skew is detected between two of the signals; an offset controller for receiving the detected skew amount, and for providing a delay control signal in response thereto; and a skew delay circuit that receives the signals and the delay control signal, and enables one or more delay stages in a path of a first arriving of the two skewed signals based on the delay control signal, such that an adjusted skew between the two skewed signals at an output of the skew delay circuit is less than the detected skew amount by an amount corresponding to the enabled one or more delay stages.

Claims

1. A skew adjustor, comprising:

a skew detector configured to receive a plurality of signals from a cable, and to provide a detected skew amount when skew is detected between two of the plurality of signals;

an offset controller configured to receive the detected skew amount, and to provide a delay control signal in response thereto; and

a skew delay circuit configured to receive the plurality of signals and the delay control signal, and to enable one or more delay stages in a path of a first arriving of the two skewed signals based on the delay control signal, such that an adjusted skew between the two skewed signals at an output of the skew delay circuit is less than the detected skew amount by an amount corresponding to the enabled one or more delay stages.

2. The skew adjustor of claim 1, wherein the plurality of signals comprises a differential signal pair, and the two skewed signals comprise positive and negative signals in the differential signal pair.

3. The skew adjustor of claim 1, further comprising an equalizer coupled to the output of the skew delay circuit.

4. The skew adjustor of claim 3, further comprising a limiting input amplifier (LIA) coupled to an output of the equalizer.

5. The skew adjustor of claim 1, wherein each of the delay stages comprises a predetermined fixed delay.

6. The skew adjustor of claim 1, wherein each of the delay stages comprises an adjustable delay.

7. The skew adjustor of claim 1, wherein the skew detector comprises a phase detector.

8. The skew adjustor of claim 2, wherein the skew delay circuit comprises four delay stages for each of the positive and negative signals in the differential signal pair.

9. The skew adjustor of claim 8, wherein the delay control signal is three bits wide.

10. The skew adjustor of claim 1, being implemented in a connector of a cable.

11. The skew adjustor of claim 1, being implemented in a receiver, wherein a transmitter and the receiver are coupled via the cable.

12. The skew adjustor of claim 1, wherein a difference between the adjusted skew and the detected skew is less than about 150 ps.

13. A method of adjusting skew, the method comprising:

receiving a plurality of signals in a skew detector, the signals being from a cable coupled to a transmitter;

detecting a skew amount between two of the plurality of signals in the skew detector;

providing a delay control signal from an offset controller that receives the detected skew amount; and

enabling one or more delay stages in a path of a first arriving of the two skewed signals based on the delay control signal, such that an adjusted skew between the two skewed signals at an output of the skew delay circuit is less than the detected skew amount by an amount corresponding to the enabled one or more delay stages.

14. The method of claim 13, wherein the receiving the plurality of signals comprises receiving a differential signal pair, and the two skewed signals comprise positive and negative signals in the differential signal pair.

15. The method of claim 13, further comprising equalizing the output of the skew delay.

16. The method of claim 15, further comprising amplifying the equalized output.

17. The method of claim 13, wherein the detecting the skew amount comprises using a phase detector.

18. The method of claim 13, further comprising adjusting a delay of one or more of the delay stages.

19. The method of claim 13, wherein the enabling of the delay stages comprises adding a predetermined fixed delay amount.

20. An apparatus, comprising:

means for receiving a plurality of signals in a skew detector, the signals being from a cable coupled to a transmitter;

means for detecting a skew amount between two of the plurality of signals in the skew detector;

means for providing a delay control signal from an offset controller that receives the detected skew amount; and

means for enabling one or more delay stages in a path of a first arriving of the two skewed signals based on the delay control signal, such that an adjusted skew between the two skewed signals at an output of the skew delay circuit is less than the detected skew amount by an amount corresponding to the enabled one or more delay stages.