Isolation system with digital communication across a capacitive barrier

• US 7,154,940 B2
• Filed: 06/25/2003
• Issued: 12/26/2006
• 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): Kim, Kevin
• Application Number:
  US10/606,231
• Publication Number:
  US 20040096006A1
• Time in Patent Office: 1,280 Days
• Field of Search: 375/220, 379/399.01, 379/412
• 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 bidirectional isolation system for providing an isolated 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 system comprising:

(a) a powered system on a first side of the isolation barrier, the powered system comprising a first driver circuit connected 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; and

(b) an isolated system on a second side of the isolation barrier, the isolated system comprising a second driver circuit connected to the isolation barrier for driving a reverse direction digital differential signal across the first isolation capacitor and the second isolation capacitor;

wherein the forward direction digital differential signal and the reverse direction digital differential signal are both driven 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 the isolated system receives power from the powered system from across the isolation barrier; and

wherein the isolated system receives a clock signal from the powered system through at least one of the plurality of isolation elements.

2. The isolation system of claim 1, wherein the first and second driver circuits are differential driver circuits that drive the respective forward direction and reverse direction digital differential signals across the first and second isolation capacitors.

3. The isolation system of claim 1, wherein the first and second driver circuits are differential driver circuits.

4. The isolation system of claim 1 wherein the forward direction digital differential signal comprises said data signal multiplexed with a control signal.

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

6. The isolation system of claim 1, wherein the isolated system receives a clock signal from the powered system through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

7. The isolation system 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.

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

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

10. A bidirectional isolation system for providing an isolated 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 system comprising:

(a) a powered system on a first side of the isolation barrier, the powered system comprising a first driver circuit connected 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; and

(b) an isolated system on a second side of the isolation barrier, the isolated system comprising a second driver circuit connected to the isolation barrier for driving a reverse direction digital differential signal across the first isolation capacitor and the second isolation capacitor;

wherein the forward direction digital differential signal and the reverse direction digital differential signal are both driven 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 the isolated system receives power from the powered system from across the isolation barrier to generate at least one power supply within the isolated system;

wherein the isolated system receives a clock signal from the powered system through at least one of the plurality of isolation elements that is separate from the first isolation capacitor and the second isolation capacitor; and

wherein at least one of the forward direction digital differential signal and the reverse direction digital differential signal includes both data and control information.

11. The isolation system of claim 10, wherein the first and second driver circuits are differential driver circuits that drive the respective forward direction and reverse direction digital differential signals across the first and second isolation capacitors.

12. The isolation system of claim 10, wherein the first and second driver circuits are differential driver circuits.

13. The isolation system of claim 10, wherein the forward direction digital differential signal comprises said data signal multiplexed with a control signal.

14. The isolation system of claim 13, wherein the reverse direction digital differential signal comprises said data signal multiplexed with a control signal.

15. The isolation system of claim 10, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

16. The isolation system of claim 10, wherein a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

17. An isolation system for providing a digital communication channel for data signals and control signals, the isolation system comprising:

an isolation barrier comprising a plurality of isolation elements;

a first multiplexer located on one side of the isolation barrier and connected to receive the data signals and the control signals and providing a first multiplexed digital differential signal that is connected 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;

a first demultiplexer located on the other side of the isolation barrier and connected 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;

wherein one side of the isolation barrier is an isolated side that receives power from across the isolation barrier; and

wherein the isolated side receives a clock signal from across the isolation barrier through at least one of the plurality of isolation elements.

18. The system of claim 17, further comprising

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

a second demultiplexer located on said one side of the isolation barrier and connected 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.

19. The system of claim 17, wherein the first multiplexed digital differential signal includes both data information and control information.

20. The system of claim 18, 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.

21. The system of claim 17, wherein the isolated side receives a clock signal from across the isolation barrier through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

22. The system of claim 17, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

23. The system of claim 17, wherein a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

24. An isolation system for providing a digital communication channel for data signals and control signals, the isolation system comprising:

an isolation barrier comprising a plurality of isolation elements;

a first multiplexer located on one side of the isolation barrier and connected to receive the data signals and the control signals and providing a first multiplexed digital differential signal that is connected 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; and

a first demultiplexer located on the other side of the isolation barrier and connected 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 control signal output,

wherein one side of the isolation barrier is an isolated side that receives power from across the isolation barrier to generate at least one power supply; and

wherein the isolated side receives a clock signal from across the isolation barrier through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

25. The system of claim 24, further comprising

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

a second demultiplexer located on said one side of the isolation barrier and connected 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.

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

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

28. A bidirectional isolation system for providing an isolated 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 system comprising:

a powered system on a first side of the isolation barrier, the powered system connected 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; and

an isolated system on a second side of the isolation barrier, the isolated system connected to the isolation barrier for driving a reverse direction digital differential signal across the first isolation capacitor and the second isolation capacitor;

wherein the forward direction digital differential signal and the reverse direction digital differential signal are both driven 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 the isolated system receives at least some power from the powered system from across the isolation barrier; and

wherein the isolated system receives a clock signal from the powered system through at least one of the plurality of isolation elements.

29. The isolation system of claim 28, wherein the forward direction digital differential signal comprises the data signal multiplexed with a control signal.

30. The isolation system of claim 29, wherein the reverse direction digital differential signal comprises said data signal multiplexed with a control signal.

31. The isolation system of claim 28, wherein the isolated system receives a clock signal from the powered system through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

32. The isolation system of claim 28, wherein at least one of the forward direction digital differential signal and the reverse direction digital differential signal includes both data and control information.

33. The isolation system of claim 28, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

34. The isolation system of claim 28, wherein a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

35. A bidirectional isolation system for providing an isolated 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 system comprising:

a powered system on a first side of the isolation barrier, the powered system connected 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; and

an isolated system on a second side of the isolation barrier, the isolated system connected to the isolation barrier for driving a reverse direction digital differential signal across the first isolation capacitor and the second isolation capacitor;

wherein the forward direction digital differential signal and the reverse direction digital differential signal are both driven 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 the isolated system receives at least some power from the powered system from across the isolation barrier to generate at least one power supply within the isolated system;

wherein the isolated system receives a clock signal from the powered system through at least one of the plurality of isolation elements that is separate from the first isolation capacitor and the second isolation capacitor; and

wherein at least one of the forward direction digital differential signal and the reverse direction digital differential signal includes both data and control information.

36. The isolation system of claim 35, wherein the forward direction digital differential signal comprises the data signal multiplexed with a control signal.

37. The isolation system of claim 36, wherein the reverse direction digital differential signal comprises said data signal multiplexed with a control signal.

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

39. The isolation system of claim 35, wherein a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

40. An isolation system for providing a digital communication channel for telephone line data signals and control signals, the isolation system comprising:

an isolation barrier comprised of a plurality of isolation elements;

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

a first demultiplexer located on the other side of the isolation barrier and connected 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; and

power circuitry on the telephone line side of the isolation barrier coupled to at least one signal transmitted across the isolation barrier, the circuitry 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; and

wherein said other side of the isolation barrier is coupled to receive a clock signal from across the isolation barrier through at least one of the plurality of isolation elements.

41. The system of claim 40, further comprising

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

and

a second demultiplexer located on the telephone line side of the isolation barrier and connected to receive the second multiplexed digital 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.

42. The system of claim 40, wherein the first multiplexed digital differential signal includes both data information and control information.

43. The system of claim 41, 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.

44. The system of claim 40, wherein said other side of the isolation barrier is coupled to receive a clock signal from across the isolation barrier through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

45. The system of claim 40, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

46. The system of claim 40, wherein a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

47. An isolation system for providing a digital communication channel for telephone line data signals and control signals, the isolation system comprising:

an isolation barrier comprised of a plurality of isolation elements;

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

a first demultiplexer located on the other side of the isolation barrier and connected 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;

power circuitry on the telephone line side of the isolation barrier coupled to at least one signal transmitted across the isolation barrier, the circuitry 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; and

wherein said other side of the isolation barrier is coupled to receive a clock signal from across the isolation barrier through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

48. The system of claim 47, further comprising

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

and

a second demultiplexer located on the telephone line side of the isolation barrier and connected to receive the second multiplexed digital 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.

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

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