Analog isolation system with digital communication across a capacitive barrier

• US 6,225,927 B1
• Filed: 12/13/1999
• Issued: 05/01/2001
• Est. Priority Date: 04/22/1997
• Status: Expired due to Term

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Scott, Jeffrey W., Welland, David R., Sooch, Navdeep S.
• Primary Examiner(s): JEAN PIERRE, PEGUY
• Application Number:
  US09/460,444
• Time in Patent Office: 505 Days
• Field of Search: 341/143, 341/155, 341/110, 379/412, 379/399
• US Class Current: 341/110
• CPC Class Codes: H04B 14/062 using delta modulation or one-bit differential modulation [1DPCM]
• 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 conveying a signal across an isolation barrier, comprising:

providing transmitting circuit operable to communicate with a capacitive isolation barrier and a signal source, the transmitting circuit being electrically isolated from a receiving circuit;

utilizing information transmitted across the capacitive isolation barrier to provide a receiving circuit clock within the receiving circuit, the information transmitted across the capacitive isolation barrier including clock information; and

extracting power from the information transmitted across the capacitive barrier to provide a power supply for at least a portion of a phone line side circuitry.

2. The method of claim 1 wherein the information transmitted across the capacitive isolation barrier further comprises data from the signal source.

3. The method of claim 1 wherein circuitry utilized to extract the power from the information is coupled to at least a first input/output node of the receiving circuit, the first node operable to be coupled to at least one capacitor of the capacitive isolation barrier, the clock information also being received through the first node.

4. An isolation system for communicating information across a capacitive isolation barrier in a digital format, comprising:

isolated line side circuitry operable to communicate digitally with the capacitive isolation barrier through at least one bidirectional connection;

power supply generation circuitry within the isolated side circuitry, the power supply generation circuitry coupled to at least one portion of the isolated side circuitry to provide a power supply to the at least one portion, the power supply generation circuitry operable to generate power from information transmitted across the capacitive isolation barrier; and

at least one clock signal within the isolated side circuitry, the clock signal being generated from clock information transmitted across the capacitive isolation barrier.

5. The isolation system of claim 4, further comprising clock circuitry within the isolated side circuitry, the power supply generation circuitry and the clock circuitry being coupled to at least one input node of the isolated side circuitry, the at least one input node being configured to be coupled to one capacitive element of the capacitive isolation barrier.

6. The isolation system of claim 4, the isolated side circuitry further comprising at least one digital to analog converter circuit operable to receive data transmitted across the capacitive isolation barrier in a pulse density modulated format.

7. An isolation system, comprising:

powered side circuitry operable to communicate digitally with isolated side circuitry, said digital communication comprising digital data transmitted from a bidirectional first input/output node, the first input/output node being within the powered side circuitry, the first input/output node capable of communicating with a capacitive isolation barrier;

isolated side circuitry operable to communicate digitally with the powered side circuitry, said digital communication comprising a digital data transmitted from a bidirectional second input/output node, the second input/output node being within the isolated side circuitry, the second input/output node capable of communicating with the capacitive isolation barrier;

a clock signal within the isolated side circuitry, the clock signal capable of being generated from information transmitted across the capacitive isolation barrier;

at least one power supply within the isolated side circuitry, the power supply capable of being, generated from information transmitted across the capacitive isolation barrier; and

at least one control signal within the isolated side circuitry, the control signal being capable of being transmitted across the capacitive isolation barrier.

8. The isolation system of claim 7, the digital data being transmitted in a pulse density modulation format.

9. The isolation system of claim 8, the control signal being encoded within information capable of being transmitted across the capacitive isolation barrier.

10. The isolation system of claim 9, the control information being encoded within the digital data.

11. The isolation system of claim 9, the power supply and the clock signal capable of being generated from information transmitted through at least one common capacitor of the capacitive isolation barrier.

12. The isolation system of claim 7, the power supply and the clock signal capable of being generated from information transmitted through at least one common capacitor of the capacitive isolation barrier.

13. The isolation system of claim 7, the control signal being encoded within information capable of being transmitted across the capacitive isolation barrier.

14. An isolation system for communicating telephone line analog signal information across an isolation barrier in digital format, the isolation system including phone line side circuitry and powered side circuitry, the isolation system comprising:

an analog-to-digital converter having a digital output, the analog to digital converter having an input connected to an analog signal containing the telephone line analog signal information to be communicated across the isolation barrier;

control information, the control information being combined with a digital output signal of the analog-to-digital converter to form a combined signal;

an isolation barrier comprised of one or more capacitive isolation elements, the isolation barrier coupled to the combined signal;

a digital-to-analog converter having an input coupled to the isolation barrier, the digital-to-analog converter providing an analog output signal to be transmitted to the telephone line; and

a power supply circuit located within the phone line side circuitry, the power supply circuit generating a DC power supply from a digital signal received across at least one of the capacitive isolation elements.

15. The isolation system of claim 14, wherein the analog-to-digital converter and the digital-to-analog converter are synchronized to a common clock signal.

16. The isolation system of claim 14, wherein the power supply circuit is coupled to at least a first node within the phone line side circuitry, clock information being communicated through the first node.

17. The isolation system of claim 16, wherein at least one capacitive isolation element is a bidirectional isolation element.

18. The isolation system of claim 14, wherein at least one capacitive isolation element may receive information to be driven in a forward and reverse direction.

19. The isolation system of claim 14, further comprising a multiplexer having a first input coupled to the digital output of the analog-to-digital converter, a second input coupled to receive the control information, and an output coupled to the isolation barrier.

20. The isolation system of claim 14, further comprising at least one clock signal within the phone line side circuitry, the at least one clock signal being generated from clock information transmitted across the isolation barrier.

21. An isolation system for communicating analog telephone line signal information across an isolation barrier in digital format, the isolation system including phone line side circuitry and powered side circuitry, comprising:

an analog-to-digital converter having a digital output signal, the analog to digital converter having an input connected to an analog signal containing the analog telephone line signal information to be communicated across the isolation barrier;

an isolation barrier comprised of one or more capacitive isolation elements, at least one of the capacitive isolation elements transmitting data in both a forward direction and a reverse direction, the isolation barrier having a phone line side coupled to the analog-to-digital converter digital output;

a digital-to-analog converter having an input coupled to the phone line side of the isolation barrier, the digital-to-analog converter providing an analog output signal; and

power circuitry located within the phone line side circuitry, the power circuitry coupled to the isolation barrier and providing a power supply for at least a portion of the phone line side circuitry by utilizing information transmitted across the isolation barrier.

22. The isolation system of claim 21, wherein the analog-to-digital converter and the digital-to-analog converter are synchronized to a common clock signal.

23. The isolation system of claim 21, wherein at least some of the transmitting data in both the forward direction and the reverse direction comprises transmitting control information combined with digital data.

24. The isolation system of claim 21, wherein at least some of the information transmitted across at least one of the capacitive isolation elements comprises control information combined with the digital output signal.

25. The isolation system of claim 21, the power supply and a phone line side clock signal being generated from information transmitted through at least one common capacitor of the capacitive isolation barrier.

26. A method for conveying a telephone line signal from a transmitting circuit to a receiving circuit while electrically isolating the transmitting circuit from the receiving circuit, comprising:

providing a first digital signal;

combining the first digital signal with at least a second digital signal to form a combined digital signal within the transmitting circuit;

transferring the combined digital signal across a capacitive isolation barrier having at least one capacitive element, the capacitive isolation barrier providing telephone line isolation;

separating the combined digital signal into the first digital signal and the second digital signal after the combined digital signal is transferred across the isolation barrier;

utilizing the second digital signal to control at least a portion of the receiving circuit; and

providing the first digital signal to an output of the receiving circuit;

receiving a third digital signal within the transmitting circuitry, the third digital signal being transmitted across the capacitive isolation barrier; and

utilizing the third digital signal transmitted across the capacitive isolation barrier to provide a power supply for at least a portion of the phone line side circuitry.

27. The method of claim 26, further comprising bidirectionally transferring data across the at least one capacitive element.

28. The method of claim 26, wherein the third digital signal includes clock information.

29. The method of claim 28, further comprising generating a clock signal within the transmitting circuitry from the third digital signal.

30. The method of claim 29, further comprising bidirectionally transferring data across the at least one capacitive element.

31. A method for conveying telephone line signals between a phone line side circuit and a powered side circuit while electrically isolating the phone line side circuit from the powered side circuit, comprising:

providing a first digital signal in the phone line side circuit;

transferring in a first direction the first digital signal across a capacitive isolation barrier having at least one capacitive element, the capacitive isolation barrier providing telephone line isolation;

providing a second digital signal in the powered side circuit;

transferring the second digital signal in a second direction across the isolation barrier, the transferring of the first and second digital signals being across the same capacitive element; and

utilizing at least one signal transmitted across the capacitive isolation barrier to provide a power supply for at least a portion of the phone line side circuitry.

32. The method of claim 31, further comprising:

combining the first digital signal with at least a third digital signal to form a combined digital signal, the transferring of the first digital signal across the capacitive isolation barrier being accomplished by transferring the combined digital signal across the isolation barrier;

separating the combined digital signal into the first digital signal and the third digital signal after the combined digital signal is transferred across the capacitive isolation barrier; and

utilizing the third digital signal to control at least a portion of the powered side circuit.

33. The method of claim 32, wherein the at least one signal includes clock information.

34. The method of claim 33, further comprising generating a clock signal within the phone line side circuit from the at least one signal.

35. The method of claim 31, wherein the at least one signal includes clock information.

36. The method of claim 35, further comprising generating a clock signal within the phone line side circuit from the at least one signal.

37. The method of claim 31, the at least one signal being the second digital signal.

38. A bidirectional communication system for conveying telephone line data signals between an isolated circuit and a powered circuit while electrically isolating the powered circuit from the isolated circuit, the system comprising:

an isolation barrier including at least a first isolation capacitor coupled between the powered circuit and the isolated circuit;

the powered circuit comprising,

a powered circuit input, wherein an input signal at the powered circuit input is the data signal to be transmitted across the first isolation capacitor, and

a powered circuit input/output node coupled to a first side of the isolation capacitor, wherein an output signal at the powered circuit input/output node is a first digital signal to be transmitted across the isolation capacitor in a first direction and wherein an input signal at the powered circuit input/output node is a second digital signal transmitted across the isolation capacitor in a second direction; and

the isolated circuit comprising,

a power supply circuit coupled to the isolation barrier, the power supply circuit generating a power supply for at least a portion of the isolated circuit from at least one signal transmitted across the isolation barrier.

39. The system of claim 38, the isolated circuit further comprising:

a digital-to-analog converter having an input coupled to a second side of the isolation capacitor, the digital-to-analog converter input receiving data signals that are transmitted in the first direction, and

an analog-to-digital converter having an output coupled to the second side of the isolation capacitor, the analog-to-digital converter output transmitting data signals to the isolation capacitor in the second direction.

40. The system of claim 38, the at least one signal and the first digital signal being the same signal.

41. The system of claim 38, further comprising a second isolation capacitor, wherein the digital signals passed across the first and second capacitors are differential signals.

42. The system of claim 38, the power supply and a phone line side clock signal being generated from information transmitted through at least one common capacitor of the capacitive isolation barrier.

43. A bidirectional isolation system for providing an isolated communication channel for communicating telephone line data signals in a forward direction and in a reverse direction across an isolation barrier comprised of at least one capacitive isolation element, the system comprising:

a powered system on a first side of the isolation barrier, the powered system comprising an output driving a forward direction signal across the isolation barrier; and

an isolated system on a second side of the isolation barrier, the isolated system comprising an output for driving a reverse direction signal across the isolation barrier;

wherein the forward direction signal and the reverse direction signal are both driven through the same capacitive isolation element; and

a power supply circuit located within the isolated system, the power supply circuit generating a DC power supply from a digital signal transmitted across the capacitive isolation barrier.

44. The isolation system of claim 43, wherein the forward direction signal comprises digital telephone line data signals multiplexed with a control signal.

45. The isolation system of claim 44, an isolated system clock signal also being generated from the digital signal received from across the capacitive isolation barrier.

46. The isolation system of claim 43, wherein the reverse direction signal comprises digital telephone line data signals multiplexed with a control signal.

47. The isolation system of claim 46, an isolated system clock signal also being generated from the digital signal received from across the capacitive isolation barrier.

48. The isolation system of claim 46, wherein the forward direction signal comprises digital telephone line data signals multiplexed with a control signal.

49. The isolation system of claim 48, an isolated system clock signal also being generated from the digital signal received from across the capacitive isolation barrier.