Low power, DC-balanced serial link transmitter

• US 20060164264A1
• Filed: 01/30/2006
• Published: 07/27/2006
• Est. Priority Date: 01/21/2005
• Status: Active Grant

• Current Assignee: Rambus Inc.
• Original Assignee: Rambus Inc.
• Inventors: Dally, William J., Poulton, John W.
• Granted Patent: US 7,268,706 B2
• Time in Patent Office: Days
• 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 data transmitter comprising:

an encoder having a data input that 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; and

a driver, coupled to the encoder, that drives 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.

2. The transmitter of claim 1, wherein the encoder comprises a Manchester encoder.

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

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

5. The transmitter 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 transmitter of claim 1, wherein the driver drives the sequence of codewords with less than 50 millivolts swing.

7. The transmitter 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 transmitter of claim 1, wherein the driver drives the sequence of codewords at a data rate sufficient to transmit more than 1 gigabit per second of the input data stream.

9. The transmitter of claim 1, wherein the encoder and the driver comprise elements on a single integrated circuit.

10. The transmitter of claim 1, including a multiplexer converting the input data stream from parallel to serial.

11. The transmitter of claim 1, including a multiplexer converting the input data stream from parallel to serial, and using a combined circuit for the multiplexer, encoder and driver.

12. The transmitter of claim 1, including a multiplexer converting the input data stream from parallel to serial, and using a combined circuit for the multiplexer, encoder and driver, wherein the combined circuit is a push-pull circuit.

13. The transmitter of claim 1, including a multiplexer converting the input data stream from parallel to serial, and using a combined circuit for the multiplexer, encoder and driver, wherein the combined circuit is a differential circuit.

14. The transmitter of claim 1, wherein the encoder comprises exclusive-OR logic.

15. The transmitter of claim 1, wherein the transmission line comprises a differential pair of conductors.

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

17. The transmitter of claim 1, wherein the transmission line comprises a twisted pair cable.

18. The transmitter of claim 1, wherein the transmission line comprises a single-ended transmission line.

19. The transmitter of claim 1, wherein the driver drives the sequence of codewords at a data rate using a clock having a frequency that is half of the data rate.

20. The transmitter of claim 1, including a differentiating circuit arranged to couple the driver to the transmission line.