Isolation system with digital communication across a capacitive barrier

• US 7,203,224 B2
• Filed: 06/23/2003
• Issued: 04/10/2007
• 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): Ha; Dac
• Assistant Examiner(s): Joseph; Jaison
• Application Number:
  US10/601,411
• Publication Number:
  US 20040081232A1
• Time in Patent Office: 1,387 Days
• Field of Search: 375/219, 375/220, 375/222, 375/257, 375/258, 375/259, 340/419, 340/421, 379/399, 379/402, 379/405, 379/412, 379/416, 379/417, 379/414, 379/406.01, 379/406.05, 379/406.06
• 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 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 a plurality of 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 differential signal across at least two of the isolation barrier elements, the at least two isolation barrier elements comprising at least a first isolation capacitor and a second isolation capacitor;

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 differential signal across the first isolation capacitor and the second isolation capacitor;

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 first and second isolation capacitors so that the first and second isolation capacitors bidirectionally transfer the forward direction and reverse direction digital differential signals;

configuring the powered system to provide a clock signal to the isolated system through at least one of the plurality of isolation elements;

configuring the powered system and the isolated system so that power is capable of being provided from the powered system to the isolated system; and

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

2. The method of claim 1, wherein the clock signal is provided from the powered system to the isolated system through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

3. The method of claim 1, wherein at least one of the forward direction digital differential signal and the reverse direction digital differential signal includes both data and control information.

4. The method of claim 1, wherein the forward direction digital differential signal comprises the data signal multiplexed with a control signal.

5. The method of claim 4, wherein the reverse direction digital differential signal comprises said data signal multiplexed with a control signal.

6. The method of claim 1, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

7. The method of claim 1, wherein a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

8. 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 a plurality of 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 differential signal across at least two of the isolation barrier elements, the at least two isolation barrier elements comprising at least a first isolation capacitor and a second isolation capacitor;

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 differential signal across the first isolation capacitor and the second isolation capacitor;

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 first and second isolation capacitors so that the first and second isolation capacitors bidirectionally transfer the forward direction and reverse direction digital differential signals, wherein at least one of the forward direction digital differential signal and the reverse direction digital differential signal includes both data and control information;

configuring the powered system to provide a clock signal to the isolated system through at least one of the plurality of isolation elements, wherein the clock signal is provided from the powered system to the isolated system through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor;

configuring the powered system and the isolated system so that power is capable of being provided from the powered system to the isolated system to generate at least one power supply within the isolated system; and

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

9. The method of claim 8, wherein the forward direction digital differential signal comprises the data signal multiplexed with a control signal.

10. The method of claim 9, wherein the reverse direction digital differential signal comprises said data signal multiplexed with a control signal.

11. The method of claim 8, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

12. The method of claim 8, wherein a portion of said plurality of isolation elements of said isolation baffler each comprises a capacitor.

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

providing a first multiplexer located on the telephone line side of the isolation barrier to receive the telephone line data signals and the control signals, the first multiplexer providing a first multiplexed digital differential signal that is to be coupled to at least two of the isolation baffler elements, the at least two isolation baffler elements comprising at least a first isolation capacitor and a second isolation capacitor;

providing a first demultiplexer located on the other side of the isolation baffler, the first demultiplexer configured to receive the first multiplexed digital differential signal from the first isolation capacitor and the second isolation capacitor, wherein bidirectional communication exists through the first and second isolation capacitors and wherein the first demultiplexer has a data signal output and a control signal output;

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; and

providing a clock signal on the telephone line side of the isolation barrier, the clock signal being transmitted across the isolation barrier through at least one of the plurality of isolation elements.

14. The method of claim 13, 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 second multiplexed digital differential signal that is connectable to the first isolation capacitor and the second isolation capacitor; and

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

whereby the first and second multiplexed digital differential signals are transmitted across the same first and second isolation capacitors so that bidirectional multiplexed communication of data and control signals across the isolation barrier is enabled.

15. The method of claim 13, wherein the first multiplexed digital differential signal includes both data information and control information.

16. The method of claim 14, wherein at least one of the first multiplexed digital differential signal and the second multiplexed digital differential signal includes both data information and control information.

17. The method of claim 13, wherein the clock signal is transmitted across the isolation barrier through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

18. The method of claim 13, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

19. The method of claim 13, wherein a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

20. 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 first multiplexer located on the telephone line side of the isolation barrier to receive the telephone line data signals and the control signals, the first multiplexer providing a first multiplexed digital differential signal that is to be coupled to at least two of the isolation barrier elements, the at least two isolation barrier elements comprising at least a first isolation capacitor and a second isolation capacitor, and wherein the first multiplexed digital differential signal includes both data information and control information;

providing a first demultiplexer located on the other side of the isolation barrier, the first demultiplexer configured to receive the first multiplexed digital differential signal from the first isolation capacitor and the second isolation capacitor, wherein bidirectional communication exists through the first and second isolation capacitors and wherein the first demultiplexer has a data signal output and a control signal output;

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; and

providing a clock signal on the telephone line side of the isolation barrier, the clock signal being transmitted across the isolation barrier through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

21. The method of claim 20, further comprising:

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

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

whereby the first and second multiplexed digital differential signals are transmitted across the same first and second isolation capacitors so that bidirectional multiplexed communication of data and control signals across the isolation barrier is enabled.

22. The method of claim 20, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

23. The method of claim 20, wherein a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

24. A method of transmitting a digital data signal across a telephone line isolation barrier comprised of a plurality of isolation elements, the method comprising:

providing first and second isolation capacitors as at least part of the plurality of isolation elements of the telephone line isolation barrier;

providing at least one digital differential signal to at least two of the isolation barrier elements at a first side of the telephone line isolation barrier, the at least two isolation barrier elements comprising at least said first isolation capacitor and said second isolation capacitor;

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;

wherein bidirectional communication exists through the first and second isolation capacitors.

25. The method of claim 24, 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.

26. The method of claim 24, wherein the at least one digital differential 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.

27. The method of claim 26, the digital data signal passing through said first and second isolation capacitors of the telephone line isolation barrier and the at least one signal utilized to produce the clock signal passing through a third isolation element of the telephone line isolation barrier.

28. The method of claim 27, the third isolation element being a capacitor.

29. The method of claim 24, further comprising combining the digital differential signal with control information to be transmitted across the isolation barrier, and separating the digital differential signal from the control information within circuitry on a phone line side of the isolation barrier.

30. The method of claim 26, wherein the system is configured to transmit digital differential information in a forward direction and a reverse direction through the same first and second isolation capacitors so that the first and second isolation capacitors bidirectionally transfer the digital differential information in the forward and reverse directions.

31. The method of claim 26, wherein the system is configured to transmit digital differential information in a forward direction and a reverse direction through a plurality of isolation capacitors.

32. The method of claim 24, wherein the at least one digital differential signal includes both data information and control information.

33. The method of claim 30, wherein the digital differential information transmitted in at least one of the forward direction or the reverse direction through the first and second isolation capacitors includes both data information and control information.

34. The method of claim 24, wherein the clock signal is produced from a received isolated signal that is transmitted across the isolation barrier through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

35. The method of claim 24, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

36. The method of claim 24, wherein a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

37. A method of transmitting a digital data signal across a telephone line isolation barrier comprised of a plurality of isolation elements, the method comprising:

providing first and second isolation capacitors as at least part of the plurality of isolation elements of the telephone line isolation barrier;

providing at least one digital differential signal to at least two of the isolation barrier elements at a first side of the telephone line isolation baffler, the at least two isolation baffler elements comprising at least said first isolation capacitor and said second isolation capacitor, and wherein the at least one digital differential signal includes both data information and control information;

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, the at least one of the received isolated signals from which the clock signal is produced being transmitted across the isolation barrier through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor;

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;

wherein bidirectional communication exists through the first and second isolation capacitors.

38. The method of claim 37, 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.

39. The method of claim 37, wherein the at least one digital differential 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.

40. The method of claim 39, the digital data signal passing through said first and second isolation capacitors of the telephone line isolation barrier and the at least one signal utilized to produce the clock signal passing through a third isolation element of the telephone line isolation barrier.

41. The method of claim 40, the third isolation element being a capacitor.

42. The method of claim 37, further comprising combining the digital differential signal with control information to be transmitted across the isolation barrier, and separating the digital differential signal from the control information within circuitry on a phone line side of the isolation barrier.

43. The method of claim 39, wherein the system is configured to transmit digital differential information in a forward direction and a reverse direction through the same first and second isolation capacitors so that the first and second isolation capacitors bidirectionally transfer the digital differential information in the forward and reverse directions.

44. The method of claim 39, wherein the system is configured to transmit digital differential information in a forward direction and a reverse direction through a plurality of isolation capacitors.

45. The method of claim 37, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

46. The method of claim 37, wherein a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

47. A method of transmitting a digital data signal across a telephone isolation barrier having a plurality of isolation elements, comprising:

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

driving the digital encoded differential signal across at least two of the isolation barrier elements, the at least two isolation barrier elements comprising at least a first isolation capacitor and a second isolation capacitor;

receiving an isolated encoded differential signal from across the first isolation capacitor and the second isolation capacitor, wherein the digital encoded differential signal and the isolated encoded differential signal are transmitted across the same first and second isolation capacitors so that the first and second isolation capacitors bidirectionally transfer the digital encoded differential signal and the isolated encoded differential signal;

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

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

separating the isolated encoded differential 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.

48. The method of claim 47, 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.

49. The method of claim 47, wherein the digital encoded differential signal does not contain the clock information.

50. The method of claim 47, wherein at least one of the digital encoded differential signal and the isolated encoded differential signal includes both data and control information.

51. The method of claim 47, wherein the clock signal is produced from clock information that is transmitted across the isolation barrier through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

52. The method of claim 47, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

53. The method of claim 47, wherein a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

54. A method of transmitting a digital data signal across a telephone isolation barrier having a plurality of isolation elements, comprising:

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

driving the digital encoded differential signal across at least two of the isolation barrier elements, the at least two isolation barrier elements comprising at least a first isolation capacitor and a second isolation capacitor;

receiving an isolated encoded differential signal from across the first isolation capacitor and the second isolation capacitor, wherein the digital encoded differential signal and the isolated encoded differential signal are transmitted across the same first and second isolation capacitors so that the first and second isolation capacitors bidirectionally transfer the digital encoded differential signal and the isolated encoded differential signal, and wherein at least one of the digital encoded differential signal and the isolated encoded differential signal includes both data and control information;

receiving clock information from across the telephone isolation barrier to provide an isolated clock signal, the clock information being transmitted across the isolation barrier through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor;

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

separating the isolated encoded differential 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.

55. The method of claim 54, 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.

56. The method of claim 54, wherein the digital encoded differential signal does not contain the clock information.

57. The method of claim 54, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

58. The method of claim 54, wherein a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.