Isolation system with digital communication across a capacitive barrier

• US 6,611,553 B1
• Filed: 06/09/2000
• Issued: 08/26/2003
• Est. Priority Date: 04/22/1997
• Status: Expired due to Fees

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Scott, Jeffrey W., Welland, David R., Sooch, Navdeep S.
• Primary Examiner(s): Le, Amanda T.
• Application Number:
  US09/591,684
• Time in Patent Office: 1,173 Days
• Field of Search: 375/220, 375/258, 375/359, 375/377, 375/219, 375/222, 375/257, 375/259, 375/354, 379/399, 379/412, 341/110, 341/143
• US Class Current: 375/220
• CPC Class Codes: H04L 25/0266 Arrangements for providing Galvanic isolation, e.g. by means of magnetic or capacitive coupling
• CPC Class Codes: H04L 25/06 Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
• CPC Class Codes: H04L 7/033 using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
• CPC Class Codes: H04M 11/06 Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors

Abstract

An isolation system is provided that is suitable for use in telephony, medical instrumentation, industrial process control and other applications. Preferred embodiments of the invention comprise a capacitive isolation barrier across which a digital signal is communicated. The system provides a means of communication across the isolation barrier that is highly immune to amplitude and phase noise interference. Clock recovery circuitry may be employed on one side of the isolation barrier to extract timing information from the digital signal communicated across the barrier, and to filter the effects of phase noise introduced at the barrier. Delta-sigma converters may be disposed on both sides of the isolation barrier to convert signals between analog and digital domains. An isolated power supply may also be provided on the isolated side of the barrier, whereby direct current is generated in response to the digital data received across the isolation barrier. Finally, a bidirectional isolation system is provided whereby bidirectional communication of digital signals is accomplished using a single pair of isolation capacitors. In preferred embodiments, the digital data communicated across the barrier consists of digital delta-sigma data signals multiplexed in time with other digital control, signaling and framing information.

Claims

1. A method of transmitting a digital data signal across a capacitive telephone line isolation barrier, comprising:

providing one or more isolation capacitors as at least part of the capacitive telephone line isolation barrier;

providing at least one digital signal to a first side of the isolation barrier;

receiving one or more isolated signals from a second side of the isolation barrier;

producing a clock signal from at least one of the isolated signals;

synchronizing at least one isolated signal with the clock signal; and

generating a DC power supply from at least one isolated signal received across at least one capacitor of the capacitive telephone line isolation barrier.

2. The method of claim 1, wherein the at least one isolated signal utilized to generate the DC power supply is also the at least one isolated signal utilized to produce the clock signal.

3. The method of claim 2, wherein the at least one isolated signal utilized to generate the DC power supply, the at least one isolated signal utilized to produce the clock signal, and the at least one isolated signal synchronized to the clock signal are all the same isolated signal.

4. The method of claim 1, wherein the at least one digital signal is the digital data signal, the at least one signal utilized to produce the clock signal being a different signal than the digital data signal.

5. The method of claim 4, the digital data signal passing through a first isolation element of the capacitive telephone line isolation barrier and the at least one signal utilized to produce the clock signal passing through a second isolation element of the capacitive telephone line isolation barrier.

6. The method of claim 5, the first and second isolation elements being capacitors.

7. The method of claim 4, wherein the system is configured to transmit information in a forward direction and a reverse direction through the same isolation capacitor.

8. The method of claim 7, wherein the system is configured to transmit information in a forward direction and a reverse direction through each of a plurality of the isolation capacitors.

9. The method of claim 1, further comprising combining the digital signal with control information to be transmitted across the isolation barrier, and separating the digital signal from the control information within circuitry on a phone line side of the isolation barrier.

10. A method of transmitting a digital data signal across a telephone isolation barrier having one or more isolation capacitors, comprising:

combining the digital data signal with control information to form a digital encoded signal;

driving the digital encoded signal across one or more of the isolation capacitors of the isolation barrier;

receiving an isolated encoded signal from across one or more the isolation capacitors;

receiving clock information from across one or more of the isolation capacitors to provide an isolated clock signal;

synchronizing the isolated encoded signal with the isolated clock signal;

separating the isolated encoded signal into an isolated digital data signal and isolated control information; and

generating a DC power supply signal from at least one signal transmitted across one or more of the isolation capacitors.

11. The method of claim 10, wherein the at least one signal utilized to generate the DC power supply also contains the clock information utilized to provide the isolated clock signal.

12. The method of claim 11, wherein the at least one signal utilized to generate the DC power supply and the isolated encoded signal are the same isolated signal.

13. The method of claim 11, wherein the system is configured to transmit information in a forward direction and a reverse direction through the same isolation capacitor.

14. The method of claim 13, wherein the system is configured to transmit information in a forward direction and a reverse direction through each of a plurality of the isolation capacitors.

15. The method of claim 10, wherein the digital encoded signal does not contain the clock information.

16. The method of claim 15, the digital encoded signal and the clock information being passed through different capacitors of the telephone line isolation barrier.

17. The method of claim 10, wherein the system is configured to transmit information in a forward direction and a reverse direction through the same isolation capacitor.

18. The method of claim 10, wherein the clock signal is recovered from the isolated encoded signal.

19. The method of claim 10, wherein the at least one signal utilized to generate the DC power supply signal is the isolated encoded signal.

20. A method for providing an isolated bidirectional communication channel for data signals in a forward direction and in a reverse direction across an isolation barrier comprised of one or more isolation elements, the method comprising:

providing a powered system for a first side of the isolation barrier, the powered system connectable to the isolation barrier for driving a forward direction digital signal across the isolation barrier;

providing an isolated system for a second side of the isolation barrier, the isolated system connectable to the isolation barrier for driving a reverse direction digital signal across the isolation barrier;

configuring the powered system and the isolated system to drive the forward direction digital signal and the reverse direction digital signal both through the same isolation element; and

providing at least some power to the isolated system from across the isolation barrier.

21. The method of claim 20, wherein the isolation barrier comprises one or more isolation capacitors.

22. The method of claim 21, the isolated system including a power supply circuit coupled to at least one isolation capacitor, the power supply circuit generating a power supply from at least one signal transmitted through the at least one isolation capacitor.

23. The method of claim 22, wherein the forward direction digital signal comprises the data signal multiplexed with a control signal.

24. The method of claim 20, wherein the forward direction digital signal comprises the data signal multiplexed with a control signal.

25. The method of claim 24, wherein the reverse direction digital signal comprises said data signal multiplexed with a control signal.

26. A method for providing a digital communication channel for telephone line data signals and control signals across an isolation barrier comprised of a plurality of isolation elements, the method comprising:

providing a multiplexer located on the telephone line side of the isolation barrier to receive the telephone line data signals and the control signals, the multiplexer providing a multiplexed digital signal that is to be coupled to the isolation barrier;

providing a demultiplexer located on the other side of the isolation barrier, the demultiplexer configured to receive the multiplexed digital signal from the isolation barrier, the demultiplexer having a data signal output and a control signal output; and

providing a power supply on the telephone line side of the isolation barrier that powers at least a portion of some circuitry on the telephone line side of the isolation barrier, the power supply generated from at least one signal transmitted across the isolation barrier.

27. The method of claim 26, wherein the isolation barrier comprises one or more isolation elements.

28. The method of claim 27, wherein one or more of the isolation elements has bidirectional communication through the element.

29. The method of claim 28, wherein the isolation elements include at least one isolation capacitor having bidirectional communication.

30. The method of claim 26, further comprising:

providing a second multiplexer located on said other side of the isolation barrier, the second multiplexer configured to receive data signals and control signals, the second multiplexer providing a multiplexed digital signal that is connectable to the isolation barrier;

providing a second demultiplexer located on telephone line side of the isolation barrier, the second demultiplexer configured to receive the multiplexed digital signal from the isolation barrier, the demultiplexer having a data signal output and a control signal output;

whereby bidirectional multiplexed communication of data and control signals across the isolation barrier is enabled.

31. The method of claim 30, wherein one or more of the isolation elements is a capacitor.

32. The method of claim 31, wherein the isolation elements include at least one isolation capacitor having bidirectional communication through the capacitor.

33. A method for providing digital communication across a telephone line capacitive isolation barrier having one or more capacitors, comprising:

transmitting from a first side of the isolation barrier a transmitted digital signal to be communicated across the isolation barrier;

receiving on a second side of the isolation barrier a received digital signal from the isolation barrier;

generating on the second side of the isolation barrier a clock signal, the clock signal generated from information transmitted across at least one of the capacitors; and

generating on the second side of the isolation barrier a power supply, the power supply generated from information transmitted across at least one capacitor of the isolation barrier.

34. The method of claim 33, further comprising:

transmitting from the second side of the isolation barrier a second transmitted digital signal to be communicated across the isolation barrier from the second side of the barrier to the first side of the barrier; and

receiving on a first side of the isolation barrier a second received digital signal from the isolation barrier.

35. The method of claim 34, whereby at least one capacitor has communication enabled in both directions across the capacitor.

36. The method of claim 33, wherein the transmitting is performed by a transmit circuit comprising:

a first input for receiving digital control information;

a second input for receiving digital data representing a time-varying signal; and

a mixing circuit for combining the digital control information and the digital data representing a time-varying signal to produce the transmitted digital signal to be communicated across the barrier.

37. The method of claim 36, whereby at least one capacitor has communication enabled in both directions across the capacitor.

38. The method of claim 33, wherein clock signal is generated by a clock circuit comprises a circuit having a phase locked loop circuit.

39. The method of claim 33, wherein the information transmitted across at least one of the capacitors to generate the clock signal is contained in a signal separate from the transmitted digital signal.

40. The method of claim 33, wherein the transmitted digital signal includes data to be communicated to the telephone line and wherein the transmitted digital signal passes through a first isolation element of the telephone line capacitive isolation barrier and the information transmitted across at least one of the capacitors to generate the clock signal passes through a second isolation element of the telephone line capacitive isolation barrier.

41. The method of claim 40, the first and second isolation elements both being capacitors.

42. A method of transmitting a digital data signal across a telephone line isolation barrier, comprising:

providing one or more isolation capacitors as at least part of the telephone line isolation barrier;

providing at least one digital signal to a first side of the telephone line isolation barrier;

receiving one or more isolated signals from a second side of the telephone line isolation barrier;

producing a clock signal from at least one of the received isolated signals;

synchronizing at least one isolated signal with the clock signal; and

generating a DC power supply from at least one isolated signal received across the telephone line isolation barrier.

43. The method of claim 42, wherein the at least one isolated signal utilized to generate the DC power supply is also the at least one isolated signal utilized to produce the clock signal.

44. The method of claim 43, wherein the at least one isolated signal utilized to generate the DC power supply, the at least one isolated signal utilized to produce the clock signal, and the at least one isolated signal synchronized to the clock signal are all the same isolated signal.

45. The method of claim 42, wherein the at least one digital signal is the digital data signal, the at least one signal utilized to produce the clock signal being a different signal than the digital data signal.

46. The method of claim 45, the digital data signal passing through a first isolation element of the capacitive telephone line isolation barrier and the at least one signal utilized to produce the clock signal passing through a second isolation element of the capacitive telephone line isolation barrier.

47. The method of claim 46, the first and second isolation elements being capacitors.

48. The method of claim 45, wherein the system is configured to transmit information in a forward direction and a reverse direction through the same isolation capacitor.

49. The method of claim 48, wherein the system is configured to transmit information in a forward direction and a reverse direction through each of a plurality of the isolation capacitors.

50. The method of claim 42, further comprising combining the digital signal with control information to be transmitted across the isolation barrier, and separating the digital signal from the control information within circuitry on a phone line side of the isolation barrier.

51. A method of transmitting a digital data signal across a telephone isolation barrier having one or more isolation capacitors, comprising:

combining the digital data signal with control information to form a digital encoded signal;

driving the digital encoded signal across one or more of the isolation capacitors of the isolation barrier;

receiving an isolated encoded signal from across one or more the isolation capacitors;

receiving clock information from across the telephone isolation barrier to provide an isolated clock signal;

synchronizing the isolated encoded signal with, the isolated clock signal;

separating the isolated encoded signal into an isolated digital data signal and isolated control information; and

generating a DC power supply signal from at least one signal transmitted across the telephone isolation barrier.

52. The method of claim 51, wherein the at least one signal utilized to generate the DC power supply also contains the clock information utilized to provide the isolated clock signal.

53. The method of claim 52, wherein the at least one signal utilized to generate the DC power supply and the isolated encoded signal are the same isolated signal.

54. The method of claim 52, wherein the system is configured to transmit information in a forward direction and a reverse direction through the same isolation capacitor.

55. The method of claim 54, wherein the system is configured to transmit information in a forward direction and a reverse direction through each of a plurality of the isolation capacitors.

56. The method of claim 53, wherein the digital encoded signal does not contain the clock information.

57. The method of claim 53, the digital encoded signal and the clock information being passed through different capacitors of the telephone line isolation barrier.

58. The method of claim 51, wherein the system is configured to transmit information in a forward direction and a reverse direction through the same isolation capacitor.

59. The method of claim 51, wherein the clock signal is recovered from the isolated encoded signal.

60. The method of claim 51, wherein the at least one signal utilized to generate the DC power supply signal is the isolated encoded signal.