Twisted pair communication system, apparatus and method thereof

• US 8,009,744 B2
• Filed: 06/17/2005
• Issued: 08/30/2011
• Est. Priority Date: 06/17/2005
• Status: Expired due to Fees

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Hemon, Erwan
• Primary Examiner(s): Fan; Chieh M
• Assistant Examiner(s): Lee; Siu M
• Application Number:
  US11/917,888
• Publication Number:
  US 20080200128A1
• Time in Patent Office: 2,265 Days
• Field of Search: 375/317, 375/257, 327/108, 327/109, 327/198, 327/50, 327/51, 327/52, 327/53, 327/54, 327/55, 327/56, 327/57, 327/58, 327/321, 327/379, 327/545.546, 327/389, 327/434, 327/170, 326/30, 326/82, 326/83, 326/86, 326/87, 326/88, 326/89, 326/90, 361/93.7, 361/93.9, 361/58, 361/87, 361/86, 361/91, 361/91.2
• US Class Current: 375/257
• CPC Class Codes: H04L 25/0274 Arrangements for ensuring balanced coupling
• CPC Class Codes: H04L 25/0282 Provision for current-mode coupling

Abstract

A communication system comprises a twisted pair communication link operably coupled to at least two driver stages for providing at least two independent input signals on the twisted pair communication link. The at least two independent input signals on the twisted pair communication link are summed and input to a comparator arranged to compare the summed signal to a reference value. The output of the comparator is input to the at least two driver stages. The outputs from the at least two driver stages are summed and fed back and summed with one or more of the independent input signals.

In this manner, adverse effects due to non-ideal symmetry between components in a twisted pair communication link, such as a Controller Area Network system, are reduced.

Claims

1. A communication system comprising:

a twisted pair communication link operably coupled to at least two driver stages for providing at least two independent input signals on the twisted pair communication link, wherein the at least two independent input signals on the twisted pair communication link are summed and input to a comparator arranged to compare the summed signal to a constant reference value, wherein an output of the comparator is input to the at least two driver stages and outputs from the at least two driver stages are summed together, fed back, and summed with one or more of the at least two independent input signals.

2. A communication system according to claim 1 wherein the communication system supports a Controller Area Network communication.

3. A communication system according to claim 1 wherein the comparator and the at least two driver stages are arranged to compensate for common-mode error by adding or subtracting current to be summed with the one or more of the independent input signals to substantially track the reference value.

4. A communication system according to claim 1, wherein the comparator is fast continuously-operating comparator or a ‘

time-discrete’

comparator.

5. A communication system according to claim 1, wherein the communication system encompasses a plurality of output stages of the twisted pair communication link arranged in parallel to produce one of a CAN-H output and/or one CAN-L output.

6. A communication system according to claim 5 wherein the plurality of stages are turned on in sequence.

7. Apparatus for a communication circuit comprising:

a twisted pair communication link operably coupled to at least two driver stages for providing at least two independent input signals on the twisted pair communication link, wherein the at least two independent signals on the twisted pair communication link are summed and input to a comparator that compares the summed signal to a constant reference value, wherein an output of the comparator is input to the at least two driver stages and outputs from the at least two driver stages are summed, fed back, and summed with one or more of the at least two independent input signals.

8. Apparatus for a communication circuit according to claim 7 wherein the apparatus supports Controller Area Network (CAN) communication.

9. Apparatus according to claim 7 wherein the comparator and the at least two driver stages are arranged to compensate for common-mode error by adding or subtracting current to be summed with the one or more of the independent input signals to substantially track the reference value.

10. Apparatus according to claim 7 wherein the comparator is fast continuously-operating comparator or a ‘

time-discrete’

comparator.

11. Apparatus according to claim 7 wherein the communication system encompasses a plurality of output stages of the twisted pair communication link arranged in parallel to produce one of a CAN-H output and/or one CAN-L output.

12. Apparatus according to claim 11 wherein the plurality of stages are turned on in sequence.

13. A method of reducing common-mode error in a communication system comprising a twisted pair communication link comprising the steps of:

providing at least two independent input signals on the twisted pair communication link;

summing the at least two independent input signals on the twisted pair communication link;

comparing at a comparator the summed signal to a constant reference value;

inputting an output of the comparator to at least two driver stages;

summing the outputs from the at least two driver stages;

feeding back the summed output from the at least two driver stages to one or more of the at least two independent input signals; and

summing the feedback summed output with the one or more of the at least two independent input signals.