Direct digital access arrangement circuitry and method for connecting to phone lines

• US 6,385,235 B1
• Filed: 03/04/1998
• Issued: 05/07/2002
• 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): Pham, Chi
• Assistant Examiner(s): PHU, PHUONG M
• Application Number:
  US09/035,175
• Time in Patent Office: 1,525 Days
• Field of Search: 379/412, 379/405, 379/413, 379/399, 379/377, 379/399.01, 379/399.02, 375/285, 375/222, 375/220, 375/219, 375/257, 375/259, 375/359, 375/377
• 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 1/573 Line monitoring circuits for detecting caller identification
• CPC Class Codes: H04M 1/76 Compensating for differences in line impedance
• CPC Class Codes: H04M 11/06 Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
• CPC Class Codes: H04M 19/001 Current supply source at the exchanger providing current to substations
• CPC Class Codes: H04M 19/02 providing ringing current or supervisory tones, e.g. dialling tone or busy tone
• CPC Class Codes: H04M 3/007 Access interface units for simultaneous transmission of speech and data, e.g. digital subscriber line [DSL] access interface units DSL access multiplexers H04Q11/0478, and H04L12/2856

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. Digital direct access arrangement circuitry for terminating a phone line connection, comprising:

powered side circuitry operable to communicate digitally with phone line side circuitry, said digital communication comprising a digital data stream in a pulse density modulation format transmitted across an isolation barrier;

phone line side circuitry operable to communicate digitally with powered side circuitry, said digital communication being in a pulse density modulation format transmitted across said isolation barrier; and

encode and decode circuitry coupled to said digital data stream to generate an encoded digital signal for transmission and receipt across said isolation barrier, wherein said encoded digital signal comprises control data added to said digital data stream.

2. The digital direct access arrangement circuitry of claim 1, wherein communication across said isolation barrier is bi-directional.

3. The digital direct access arrangement circuitry of claim 2, further comprising an isolation barrier coupled between said powered side circuitry and said phone line side circuitry.

4. The digital direct access arrangement circuitry of claim 2, wherein said isolation barrier comprises one or more capacitors.

5. The digital direct access arrangement circuitry of claim 2, wherein said powered side circuitry includes encode circuitry coupled to said digital data stream to generate an encoded digital signal for transmission across said isolation barrier and wherein said phone line circuitry includes decode circuitry to generate a decoded digital signal from said encoded digital signal.

6. The digital direct access arrangement circuitry of claim 5, wherein said encoded digital signal comprises framing data added to said digital data stream for data synchronization within said phone line side circuitry.

7. The digital direct access arrangement circuitry of claim 5, wherein said encoded digital signal comprises said digital data stream formatted such that said decode circuitry recovers a clock signal from said encoded digital signal.

8. The digital direct access arrangement circuitry of claim 2, wherein said phone line side circuitry includes encode circuitry coupled to said digital data to generate an encoded digital signal for transmission across said isolation barrier and said powered circuitry includes decode circuitry to generate a decoded digital signal from said encoded digital signal.

9. The digital direct access arrangement circuitry of claim 8, wherein said control data comprises phone line status information.

10. The digital direct access arrangement circuitry of claim 2, wherein said powered side circuitry has a communication interface that is capable of being coupled to an external device.

11. The digital direct access arrangement circuitry of claim 2, wherein said phone line side circuitry has analog output signals that is capable of being coupled to phone lines through hook-switch circuitry and diode bridge circuitry.

12. Powered side circuitry for digital direct access arrangement circuitry for terminating a phone line connection at a user end of a phone line, comprising:

a communication interface capable of being coupled to an external user end device;

an isolation interface capable of communicating digitally with user end phone line side circuitry through a user end isolation barrier; and

encode circuitry within said isolation interface to generate an encoded digital signal from a digital data stream for transmission across said isolation barrier, wherein said encoded digital signal comprises control data added to said digital data stream and wherein said digital data stream is in a pulse density modulation format.

14. The powered side circuitry of claim 12, wherein said encoded digital signal comprises said digital data stream formatted such that decode circuitry is capable of recovering a clock signal from said encoded digital signal.

15. The powered side circuitry of claim 12, wherein said isolation interface is capable of communicating bi-directionally across said isolation barrier.

16. The powered side circuitry of claim 12, wherein signals communicated through said communication interface comprises digital data signals, control signals and phone line status signals.

17. The powered side circuitry of claim 16, wherein said communication interface comprises a digital serial port interface.

18. The powered side circuitry of claim 12, further comprising an oversampled deltas-sigma modulator coupled to receive base-band digital data signals from said external device and to convert said base-band digital data signals to said digital data stream in a pulse density modulation format.

19. The powered side circuitry of claim 12, further comprising decode circuitry that is capable of being coupled to an encoded digital signal received from said phone line side circuitry to generate a decoded digital signal.

20. The powered side circuitry of claim 19, wherein said decoded digital signal comprises at decoded digital data stream in a pulse density modulation format, and further comprising a digital filter coupled to said decoded digital data stream to generate base-band digital data signals.

13. Powered side circuitry for digital direct access arrangement circuitry for terminating a phone line connection at a user end of a phone line, comprising:

a communication interface capable of being coupled to an external user end device;

an isolation interface capable of communicating digitally with user end phone line side circuitry through a user end isolation barrier; and

encode circuitry within said isolation interface to generate an encoded digital signal from a digital data stream for transmission across said isolation barrier, wherein said encoded digital signal comprises control data added to said digital data stream and wherein said encoded digital signal comprises framing data added to said digital data stream for data synchronization within said phone line side circuitry.

21. Phone line side circuitry for digital direct access arrangement circuitry for terminating a phone line connection, comprising:

a communication interface that is capable of being coupled to phone lines;

an isolation interface that is capable of communicating digitally with powered side circuitry through an isolation barrier; and

decode circuitry within said isolation interface to generate a decoded digital signal from an encoded digital signal received from said powered side circuitry across said isolation barrier, wherein said encoded digital signal comprises control data added to a digital data stream.

22. The phone line side circuitry of claim 21, wherein said encoded digital signal comprises a digital data stream formatted such that said decode circuitry recovers a clock signal from said encoded digital signal.

23. The phone line side circuitry of claim 21, wherein said encoded digital signal comprises framing data added to a digital data stream for data synchronization within said phone line side circuitry.

24. The phone line side circuitry of claim 21, wherein said isolation interface is capable of communicating bi-directionally across said isolation barrier.

25. The phone line side circuitry of claim 21, wherein signals communicated through said communication interface comprises analog data signals.

26. The phone line side circuitry of claim 21, wherein said communication interface is configured to be coupled to phone lines through external hook-switch circuitry and an external diode bridge.

27. The phone line side circuitry of claim 21, wherein said communication interface comprises circuitry coupled to said phone lines to detect ringing on said phone-lines and to control an off-hook state on said phone lines.

28. The phone line side circuitry of claim 27, wherein said communication interface comprises DC termination circuitry coupled to said phone lines to provide an internal DC power supply to said phone line side circuitry.

29. The phone line side circuitry of claim 21, further comprising an oversampled delta-sigma analog-to-digital converter configured to be coupled to analog signals received from said phone lines to convert said analog signals to a digital data stream in a pulse density modulation format.

30. The phone line side circuitry of claim 21, further comprising encode circuitry within said isolation interface to generate a second encoded digital signal from a second digital data stream for transmission across said isolation barrier.

31. The phone line side circuitry of claim 30, wherein said second encoded digital signal comprises second control data added to said second digital data stream.

32. The phone line side circuitry of claim 31, wherein said second control data comprises phone line status information.

33. The phone line side circuitry of claim 21, wherein said digital data signal is a digital data stream in a pulse density modulation format.

34. A method for communicating with phone lines, comprising:

converting a signal received from phone lines into a digital data stream in a pulse density modulation format;

encoding said digital data stream to generate an encoded digital data stream, wherein said encoded step comprises adding control data to the digital data stream; and

communicating said encoded digital data stream across an isolation barrier from phone line side circuitry to powered side circuitry.

35. The method of claim 34, wherein said isolation barrier comprises one or more capacitors.

36. The method of claim 35, further comprising:

communicating a digital bit stream across said isolation barrier from said powered side circuitry to said phone line side circuitry; and

recovering a clock signal within said phone line side circuitry from said digital bit stream.

37. The method of claim 35, further comprising:

decoding said digital data stream after said communicating step.

38. A method for communicating with phone lines, comprising:

converting a digital signal into a digital data stream in a pulse density modulation format;

encoding said digital data stream with control data to generate an encoded digital data stream; and

communicating said encoded digital data stream across an isolation barrier from powered side circuitry to phone line side circuitry.

39. The method of claim 38, wherein said isolation barrier comprises one or more capacitors.

40. The method of claim 39, further comprising:

recovering a clock signal within said phone line side circuitry from said digital bit stream.

41. The method of claim 39, further comprising:

decoding said digital data stream after said communicating step.

42. A method for communicating with phone lines, comprising:

generating an encoded digital signal from a digital data signal, wherein the encoded digital signal includes control data and the digital data signal; and

communicating said encoded digital signal across an isolation barrier from phone line side circuitry to powered side circuitry.

43. The method of claim 42, wherein said control data comprises phone line status information.

44. The method of claim 42, further comprising:

communicating a digital bit stream across said isolation barrier from said powered side circuitry to said phone line side circuitry; and

recovery a clock signal within said phone line side circuitry from said digital bit stream.

45. The method of claim 44, wherein said isolation barrier comprises one or more capacitors.

46. Digital direct access arrangement circuitry for terminating a phone line connection, comprising:

powered side circuitry operable to communicate digitally with phone line side circuitry, said digital communication comprising a digital data stream in a pulse density modulation format transmitted across an isolation barrier through a first bi-directional connection; and

phone line side circuitry operable to communicate digitally with powered side circuitry, said digital communication comprising a digital data stream in a pulse density modulation format transmitted across said isolation barrier through a second bi-directional connection.

47. The digital direct access arrangement circuitry of claim 46, further comprising an isolation barrier coupled between said powered side circuitry and said phone line side circuitry.

48. The digital direct access arrangement circuitry of claim 46, wherein said isolation barrier comprises one or more capacitors.

49. The digital direct access arrangement circuitry of claim 46, wherein said powered side circuitry includes encode circuitry coupled to said digital data stream to generate an encoded digital signal for transmission across said isolation barrier and wherein said phone line circuitry includes decode circuitry to generate a decoded digital signal from said encoded digital signal.

50. The digital direct access arrangement circuitry of claim 49, wherein said encoded digital signal comprises control data added to said digital data stream.

51. The digital direct access arrangement circuitry of claim 49, wherein said encoded digital signal comprises framing data added to said digital data stream for data synchronization within said phone line side circuitry.

52. The digital direct access arrangement circuitry of claim 49, wherein said encoded digital signal comprises said digital data stream formatted such that said decode circuitry recovers a clock signal from said encoded digital signal.

53. The digital direct access arrangement circuitry of claim 49, wherein said phone line side circuitry includes encode circuitry coupled to said digital data to generate an encoded digital signal for transmission across said isolation barrier and said powered circuitry includes decode circuitry to generate a decoded digital signal from said encoded digital signal.

54. The digital direct access arrangement circuitry of claim 53, wherein said encoded digital signal comprises control data added to said digital data stream.

55. The digital direct access arrangement circuitry of claim 54, wherein said control data comprises phone line status information.

56. A method for communicating with phone lines, comprising:

converting a signal received from phone lines into a digital data stream in a pulse density modulation format; and

communicating said digital data stream across an isolation barrier from a bi-directional connection on said phone line side circuitry to a bi-directional connection on said powered side circuitry.

57. The method of claim 56, wherein said isolation barrier comprises one or more capacitors.

58. The method of claim 56, further comprising:

communicating a digital bit stream across said isolation barrier from said powered side circuitry to said phone line side circuitry; and

recovering a clock signal within said phone line side circuitry from said digital bit stream.

59. The method of claim 56, further comprising encoding said digital data stream prior to said communicating step.

60. A method for communicating with phone lines, comprising:

converting a digital signal into a digital data stream in a pulse density modulation format; and

communicating said digital data stream across an isolation barrier from a bi-directional connection on said powered side circuitry to a bi-directional connection on said phone line side circuitry.

61. The method of claim 60, wherein said isolation barrier comprises one or more capacitors.

62. The method of claim 60, further comprising recovering a clock signal within said phone line side circuitry from said digital bit stream.

63. The method of claim 60, further comprising encoding said digital data stream prior to said communicating step.

64. Digital direct access arrangement circuitry for terminating a phone line connection, comprising:

powered side circuitry operable to communicate digitally with phone line side circuitry, said digital communication comprising a digital data stream transmitted across an isolation barrier through a first bi-directional connection; and

phone line side circuitry operable to communicate digitally with said powered side circuitry across said isolation barrier through a second bi-directional connection.

65. The digital direct access arrangement circuitry of claim 64, further comprising an isolation barrier coupled between said powered side circuitry and said phone line side circuitry.

66. The digital direct access arrangement circuitry of claim 64, wherein said isolation barrier comprises one or more capacitors.

67. The digital direct access arrangement circuitry of claim 64, wherein said powered side circuitry includes encode circuitry coupled to said digital data stream to generate an encoded digital signal for transmission across said isolation barrier and wherein said phone line circuitry includes decode circuitry to generate a decoded digital signal from said encoded digital signal.

68. The digital direct access arrangement circuitry of claim 67, wherein said encoded digital signal comprises control data added to said digital data stream.

69. The digital direct access arrangement circuitry of claim 67, wherein said encoded digital signal comprises framing data added to said digital data stream for data synchronization within said phone line side circuitry.

70. The digital direct access arrangement circuitry of claim 67, wherein said encoded digital signal comprises said digital data stream formatted such that said decode circuitry may recover a clock signal from said encoded digital signal.

71. The digital direct access arrangement circuitry of claim 64, wherein said phone line side circuitry includes encode circuitry coupled to said digital data to generate an encoded digital signal for transmission across said isolation barrier and said powered circuitry includes decode circuitry to generate a decoded digital signal from said encoded digital signal.

72. The digital direct access arrangement circuitry of claim 71, wherein said encoded digital signal comprises control data added to said digital data stream.

73. The digital direct access arrangement circuitry of claim 72, wherein said control data comprises phone line status information.

74. A method for communicating with phone lines, comprising:

converting a signal received from phone lines into a digital data stream; and

communicating said digital data stream across an isolation barrier from a bi-directional connection on phone line side circuitry to a bi-directional connection on powered side circuitry.

75. The method of claim 74, wherein said isolation barrier comprises one or more capacitors.

76. The method of claim 74, further comprising:

communicating a digital bit stream across said isolation barrier from said powered side circuitry to said phone line side circuitry; and

recovering a clock signal within said phone line side circuitry from said digital bit stream.

77. The method of claim 74, further comprising encoding said digital data stream prior to said communicating step.

78. A method for communicating with phone lines from a user end of the phone lines, comprising:

converting a digital signal into a digital data stream;

communicating said digital data stream across a user end isolation barrier from a bi-directional connection on user end powered side circuitry to a bi-directional connection on user end phone line side circuitry; and

recovering a clock signal within said phone line side circuitry from said digital bit stream.

79. The method of claim 78, wherein said isolation barrier comprises one or more capacitors.

80. The method of claim 78, further comprising encoding said digital data stream prior to said communicating step.

81. A method of operating digital direct access arrangement circuitry for terminating a phone line connection, comprising:

providing phone line side circuitry operable to communicate with a capacitive isolation barrier and the phone line connection;

utilizing information transmitted across the capacitive isolation barrier to provide a phone line side clock, 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 the phone line side circuitry.

82. The method of claim 81 wherein the information transmitted across the capacitive isolation barrier further comprises data to be communicated to the phone line connection.

83. The method of claim 81 wherein circuitry utilized to extract the power from the information is coupled to at least a first input or output node of the phone line side circuitry, the first node operable to be coupled to at least one capacitor of the capacitive isolation barrier, the clock information also being utilized transmitted through the first node.

84. Digital direct access arrangement circuitry for terminating a phone line connection, comprising:

phone line side circuitry operable to communicate digitally with a capacitive isolation barrier through at least one bi-directional connection;

power supply generation circuitry within the phone line side circuitry, the power supply generation circuitry coupled to at least one portion of the phone line 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 phone line side circuitry, the clock signal being generated from clock information transmitted across the capacitive isolation barrier.

85. The digital direct access arrangement circuitry of claim 84, further comprising clock circuitry within the phone line side circuitry, the power supply generation circuitry and the clock circuitry being coupled to at least one input node of the phone line side circuitry, the at least one input node being configured to be coupled to one capacitive element of the capacitive isolation barrier.

86. The digital direct access arrangement circuitry of claim 84, the phone line 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.

87. Digital direct access arrangement circuitry for terminating a phone line connection, comprising:

powered side circuitry operable to communicate digitally with phone line side circuitry, said digital communication comprising digital data transmitted from a bi-directional 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;

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

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

at least one power supply within the phone line 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 phone line side circuitry, the control signal being capable of being transmitted across the capacitive isolation barrier.

88. The digital direct access arrangement circuitry of claim 87, the digital data being transmitted in a pulse density modulation format.

89. The digital direct access arrangement circuitry of claim 88, the control signal being encoded within information capable of being transmitted across the capacitive isolation barrier.

90. The digital direct access arrangement circuitry of claim 89, the control information being encoded within the digital data.

91. The digital direct access arrangement circuitry of claim 89, 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.

92. The digital direct access arrangement circuitry of claim 87, 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.

93. The digital direct access arrangement circuitry of claim 87, the control signal being encoded within information capable of being transmitted across the capacitive isolation barrier.