Isolation system with digital communication across a capacitive barrier

• US 6,389,061 B1
• Filed: 05/15/2000
• Issued: 05/14/2002
• 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:
  US09/567,721
• Time in Patent Office: 729 Days
• Field of Search: 375/219, 375/220, 375/222, 375/257, 375/258, 375/259, 375/354, 375/377, 375/359, 379/399, 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 telephone line isolation system for providing an isolated communication channel for digital signals in a forward direction and in a reverse direction across a capacitive telephone line isolation barrier, the system comprising:

a powered system on a first side of the capacitive telephone line isolation barrier, the powered system comprising,

a powered side encoder circuit having an input terminal for receiving forward direction digital signals to be transmitted in the forward direction across at least one capacitor of the capacitive telephone line isolation barrier, and

a powered decoder circuit having an input to receive reverse direction digital signals transmitted in the reverse direction across at least one capacitor of the capacitive telephone isolation barrier, the powered decoder circuit decoding signals transmitted in the reverse direction across the capacitive telephone line isolation barrier; and

an isolated system on a second side of the capacitive telephone line isolation barrier, the isolated system comprising,

a clock circuit having an input coupled to at least one capacitor of the capacitive telephone line isolation and an output providing an isolated clock signal to circuitry in the isolated system,

an isolated decoder circuit having an input to receive forward direction digital signals transmitted in the forward direction across at least one capacitor of the capacitive telephone isolation barrier, the isolated decoder circuit decoding signals transmitted in the forward direction across the capacitive telephone line isolation barrier,

an isolated encoder circuit having an input for receiving digital signals to be transmitted in the reverse direction across at least one capacitor of the capacitive telephone isolation barrier, and

an isolated power supply circuit coupled to at least one of the isolation capacitors, the power supply circuit generating a DC power supply from at least one signal received across the capacitive isolation barrier.

2. The system of claim 1, wherein at least one capacitor of the capacitive telephone isolation barrier has information bidirectionally transferred through the same capacitor.

3. The system of claim 1, wherein the power supply and the isolated clock signal are generated, at least in part, from information transmitted through the same capacitor of the capacitive isolation barrier.

4. The system of claim 1, wherein the power supply and the isolated clock signal are generated, at least in part, from information transmitted through the same capacitor of the capacitive isolation barrier.

5. The system of claim 1, wherein the at least one signal that is utilized to generate a DC power supply includes clock information.

6. The system of claim 5, wherein the at least one signal that is utilized to generate a DC power supply is a forward direction digital signal transmitted across the capacitive telephone isolation barrier from the powered side encoder.

7. The system of claim 1, wherein the reverse direction digital signals or the forward direction digital signals are not transmitted through the at least one capacitor of the capacitive telephone line isolation that the clock circuit is coupled to.

8. An isolation system for transmitting a digital data signal across a capacitive telephone line isolation barrier, comprising:

one or more isolation capacitors;

means for providing a digital signal to a first side of the isolation barrier;

means for receiving a plurality of isolated signals from a second side of the isolation barrier;

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

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

an isolated power supply circuit coupled to at least one of the isolation capacitors, the power supply circuit generating a DC power supply from at least one of the isolated signals received across the capacitive telephone line isolation barrier.

9. The system of claim 8, 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 a clock signal.

10. The system of claim 9, wherein the at least one isolated signal utilized to generate the DC power supply, the at least one isolated signal utilized to produce a clock signal, and the at least one isolated signal synchronized to the clock signal are all the same isolated signal.

11. The system of claim 8, further comprising encoder means for combining said digital signal with control information to be transmitted across the isolation barrier, and decoder means within a phone line side of the system, the decoder means separating the digital data signal from the control information.

12. The system of claim 8, wherein the system is configured to transmit information in a forward direction and a reverse direction through the same isolation capacitor.

13. The system of claim 12, 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.

14. The method of claim 8, wherein the digital signal contains the digital data signal to be transmitted across the capacitive telephone line isolation barrier, the at least one of the isolated signals utilized to produce the clock signal being a separate signal from the digital signal.

15. The method of claim 8, the digital signal and the at least one of the isolated signals utilized to produce the clock signal being passed through different isolation capacitors of the capacitive telephone line isolation barrier.

16. An isolation system for providing a digital communication channel between a powered circuit and a phone line side circuit, the isolation system comprising:

a capacitive isolation barrier for isolating a telephone line from the powered circuit;

a clock recovery circuit located on an isolated side of the capacitive isolation barrier; and

at least one isolated signal on the isolated side of the isolation barrier, the isolated signal being transmitted across the capacitive isolation barrier;

wherein the clock recovery circuit is adapted to provide a recovered clock signal based on the at least one isolated signal received from the powered circuit across the isolation barrier, the recovered clock signal being substantially free of phase noise.

17. The isolation system of claim 16, wherein the digital communication channel is bidirectional.

18. The isolation system of claim 17, wherein at least some of the digital communication channel is bidirectional through the same capacitor.

19. The isolation system of claim 16, wherein the clock recovery circuit comprises a phase-locked loop circuit.

20. The isolation system of claim 19, wherein the phase-locked loop circuit comprises a loop filter circuit for reducing the effects of phase noise on the recovered clock signal.

21. The isolation system of claim 16, wherein the isolated signals are data signals.

22. The isolation system of claim 16, wherein the isolated signals are clock signals.

23. The isolation system of claim 16, further comprising an isolated power supply circuit coupled to at least one isolation capacitor of the capacitive isolation barrier, the power supply circuit generating a DC power supply from at least one of the isolated signals received across the at least one isolation capacitor.

24. 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 one or more 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 signal across the isolation barrier; 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 signal across the isolation barrier;

wherein the forward direction digital signal and the reverse direction digital signal are both driven through the same isolation element, and wherein the isolated system receives at least some power from across the isolation barrier.

25. The isolation system of claim 24, wherein the isolation barrier comprises one or more isolation capacitors.

26. The isolation system of claim 25, 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.

27. The isolation system of claim 26, wherein the forward direction digital signal comprises the data signal multiplexed with a control signal.

28. The isolation system of claim 24, wherein the forward direction digital signal comprises the data signal multiplexed with a control signal.

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

30. 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 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 multiplexed digital signal that is coupled to the isolation barrier;

a demultiplexer located on the other side of the isolation barrier and connected to receive the multiplexed digital signal from the isolation barrier, the demultiplexer having 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.

31. The system of claim 30, wherein the isolation barrier comprises one or more isolation elements.

32. The system of claim 31, wherein one or more of the isolation elements has bidirectional communication through the element.

33. The system of claim 32, wherein the isolation elements include at least one isolation capacitor having bidirectional communication.

34. The system of claim 30, 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 multiplexed digital signal that is connected to the isolation barrier; and

a second demultiplexer located on telephone line side of the isolation barrier and connected 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.

35. The system of claim 34, wherein one or more of the isolation elements is a capacitor.

36. The system of claim 35, wherein the isolation elements include at least one isolation capacitor having bidirectional communication through the capacitor.

37. An isolation system for providing digital communication across a telephone line capacitive isolation barrier having one or more capacitors, comprising:

a transmit circuit located on a first side of the isolation barrier for providing a transmitted digital signal to be communicated across the isolation barrier;

a receive circuit located on a second side of the isolation barrier for receiving a received digital signal from the isolation barrier;

a clock circuit located on the second side of the isolation barrier and coupled to the receive circuit, the clock circuit generating a timing signal from information transmitted across at least one of the capacitors; and

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

38. The isolation system of claim 37, further comprising:

a second transmit circuit located on the second side of the isolation barrier for providing 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

a second receive circuit located on a first side of the isolation barrier for receiving a second received digital signal from the isolation barrier.

39. The isolation system of claim 38, whereby at least one capacitor has communication enabled in both directions across the capacitor.

40. The isolation system of claim 37, wherein the transmit circuit comprises:

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.

41. The isolation system of claim 40, whereby at least one capacitor has communication enabled in both directions across the capacitor.

42. The isolation system of claim 37, wherein the clock circuit comprises a circuit having a phase locked loop circuit.

43. The method of claim 37, 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.

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