Low power, DC-balanced serial link transmitter

• US 7,061,406 B1
• Filed: 01/21/2005
• Issued: 06/13/2006
• Est. Priority Date: 01/21/2005
• Status: Active Grant

• Current Assignee: Rambus Inc.
• Original Assignee: Rambus Inc.
• Inventors: Poulton, John W., Dally, William J.
• Primary Examiner(s): PATHAK, SUDHANSHU C
• Application Number:
  US11/040,835
• Time in Patent Office: 508 Days
• Field of Search: 341/101, 341/100, 341/61, 341/70, 341/93, 341/141, 341/136, 341/50
• US Class Current: 341/50
• CPC Class Codes: H03M 5/12 Biphase level code, e.g. split phase code, Manchester code; Biphase space or mark code, e.g. double frequency code
• CPC Class Codes: H04L 25/4904 using self-synchronising codes, e.g. split-phase codes

Abstract

A transmitter for a data communication system that comprises a transmission line between first and second integrated circuits. An encoder on the first integrated circuit encodes an input data stream to produce a sequence of codewords, wherein codewords in the sequence are members of a set of codewords representing data in the input data stream, and the members of the set are substantially DC balanced, such as a Manchester encoded symbol set. An integrating circuit on the second integrated circuit integrates codewords by integrating for a first interval with a positive polarity within a particular signaling cell, and integrating for a second interval with a negative polarity within the particular signaling cell, to produce output representing the codewords. A sense circuit produces an output data stream.

Claims

1. A method for transmitting data comprising:

encoding an input data stream to produce a sequence of codewords, wherein codewords in the sequence are members of a set of codewords representing data in the input data stream, and the members of the set are substantially DC balanced; and

driving the sequence of codewords within a corresponding sequence of symbol cells on a transmission line, with power of less than 100 picoJoules per bit of data in the input data stream.

2. The method of claim 1, wherein the encoding comprises Manchester encoding.

3. The method of claim 1, wherein the set of codewords consists of two members.

4. The method of claim 1, wherein the set of codewords comprises more than two members.

5. The method of claim 1, wherein the set of codewords comprises a first subset of orthogonal code words and a second subset of code words that are complements of the orthogonal code words in the first subset.

6. The method of claim 1, including driving the sequence of codewords with less than 50 millivolts swing.

7. The method of claim 1, wherein codewords in the set of codewords include, respectively, a binary code word and one of a plurality of voltage swing amplitudes, whereby a particular binary code word with a first voltage swing amplitude represents a first data value, and the particular binary code word with a second voltage swing amplitude represents a second data value.

8. The method of claim 1, including driving the sequence of codewords at a data rate sufficient to transmit more than 1 gigabit per second of the input data stream.

9. The method of claim 1, including using resources on a single integrated circuit for the encoding and the driving.

10. The method of claim 1, including multiplexing bits in the data stream from parallel to serial prior to the encoding.

11. The method of claim 1, including multiplexing bits in the data stream from parallel to serial, and using a combined circuit for the multiplexing, encoding and driving.

12. The method of claim 1, including multiplexing bits in the data stream from parallel to serial, and using a combined circuit for the multiplexing, encoding and driving, wherein the combined circuit is a push-pull circuit.

13. The method of claim 1, including multiplexing bits in the data stream from parallel to serial, and using a combined circuit for the multiplexing, encoding and driving, wherein the combined circuit is a differential circuit.

14. The method of claim 1, wherein the transmission line comprises a differential pair of conductors.

15. The method of claim 1, wherein the transmission line comprises a single printed circuit board conductor or a differential pair of printed circuit board conductors.

16. The method of claim 1, wherein the transmission line comprises a twisted pair cable.

17. The method of claim 1, wherein the transmission line comprises a single-ended transmission line.

18. The method of claim 1, including driving the sequence of codewords at a data rate using a clock having a frequency that is half of the data rate.

19. The method of claim 1, including a coupling the sequence of codewords via a differentiating circuit to the transmission line.

20. A data transmitter comprising:

means for encoding an input data stream to produce a sequence of codewords, wherein codewords in the sequence are members of a set of codewords representing data in the data stream, and the members of the set are substantially DC balanced; and

means for driving the sequence of codewords within a corresponding sequence of symbol cells on a transmission line, with power of less than 100 picoJoules per bit of data in the data stream.

21. An article, comprising:

a program file in a computer-readable medium, comprising executable instructions implementing an integrated circuit module, the module comprising;

an encoder having a data input to encode an input data stream to produce a sequence of codewords, wherein codewords in the sequence are members of a set of codewords representing data in the input data stream, and the members of the set are substantially DC balanced; and

a driver, coupled to the encoder, to drive the sequence of codewords within a corresponding sequence of symbol cells on a transmission line, with power of less than 100 picoJoules per bit of data in the data stream.