Digital access arrangement circuitry and method for connecting to phone lines having a DC holding circuit with switchable time constants

• US 20040190670A1
• Filed: 10/03/2003
• Published: 09/30/2004
• Est. Priority Date: 04/22/1997
• Status: Active Grant

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Scott, Jeffrey W., Welland, David R., Tuttle, George Tyson, Dupuis, Timothy J., Sooch, Navdeep S.
• Granted Patent: US 7,046,755 B2
• Time in Patent Office: Days
• US Class Current: 375/377
• 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
• CPC Class Codes: H04M 19/001 Current supply source at the exchanger providing current to substations
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A digital direct access arrangement (DAA) circuitry may be used to terminate the telephone connections at the user'"'"'s end that provides a communication path for signals to and from the phone lines. Briefly described, the DAA provides a programmable means for the DC termination for a variety of international phone standards. The invention may also be utilized with means for transmitting and receiving a signal across a capacitive isolation barrier. More particularly, a DC holding circuit is provided in which a programmable DC current limiting mode is available. In the current limiting mode, power may be dissipated in devices external to a DAA integrated circuit. Moreover, much of the power may be dissipated in external passive devices, such as resistors.

Claims

1-43. -43. (Canceled)

44. A communication system, comprising:

phone line side circuitry that may be coupled to phone lines;

powered side circuitry that may be coupled to the phone line side circuitry through an isolation barrier comprised of a plurality of isolation elements; and

a DC holding circuit within the phone line side circuitry, the DC holding circuit being switchable to operate in a plurality of DC holding circuit phases, the DC holding circuit having a first time constant in at least a first DC holding circuit phase and having a second time constant in at least a second DC holding circuit phase;

wherein the powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

wherein the phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

wherein the powered side circuitry is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements; and

wherein the powered side circuitry and the phone line side circuitry are configured so that power is capable of being provided from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards.

45. The communication system of claim 44, further comprising the isolation barrier coupled between the phone line side circuitry and the powered side circuitry.

46. The communication system of claim 44, the first DC holding circuit phase occurring before the second DC holding circuit phase, wherein the first time constant is shorter than the second time constant.

47. The communication system of claim 44, the DC holding circuit operable in the first DC holding circuit phase to allow for a first settling time for establishing off-hook conditions and the second DC holding circuit phase to allow for a second settling time after the first phase, the second settling time being slower than the first.

48. The communication system of claim 47, the first time constant being less than 10 msec and the second time constant being greater than 100 msec.

49. The communication system of claim 44, the first time constant being at least an order of magnitude shorter than the second time constant.

50. The communication system of claim 44, wherein the powered side circuitry is further configured to provide the clock signal to the phone line side circuitry through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

51. The communication system of claim 44, wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

52. The communication system of claim 44, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

53. The communication system of claim 44, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

54. A communication system, comprising:

phone line side circuitry that may be coupled to phone lines;

powered side circuitry that may be coupled to the phone line side circuitry through an isolation barrier comprised of a plurality of isolation elements; and

a DC holding circuit within the phone line side circuitry, the DC holding circuit being switchable to operate in a plurality of DC holding circuit phases, the DC holding circuit having a first time constant in at least a first DC holding circuit phase and having a second time constant in at least a second DC holding circuit phase;

wherein said powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

wherein said phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

wherein the powered side circuitry is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements that is separate from the first isolation capacitor and the second isolation capacitor;

wherein the powered side circuitry and the phone line side circuitry are configured so that power is capable of being provided from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards; and

wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

55. The communication system of claim 54, further comprising the isolation barrier coupled between the phone line side circuitry and the powered side circuitry.

56. The communication system of claim 54, the first DC holding circuit phase occurring before the second DC holding circuit phase, wherein the first time constant is shorter than the second time constant.

57. The communication system of claim 54, the DC holding circuit operable in the first DC holding circuit phase to allow for a first settling time for establishing off-hook conditions and the second DC holding circuit phase to allow for a second settling time after the first phase, the second settling time being slower than the first.

58. The communication system of claim 57, the first time constant being less than 10 msec and the second time constant being greater than 100 msec.

59. The communication system of claim 54, the first time constant being at least an order of magnitude shorter than the second time constant.

60. The communication system of claim 54, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

61. The communication system of claim 54, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

69. The method of claim 61, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

62. A method of providing a communication system that may be coupled to a phone line, comprising:

coupling an isolation barrier between powered side circuitry and phone line side circuitry, the isolation barrier comprising a plurality of isolation elements;

configuring the powered side circuitry to communicate a first digital differential signal 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;

configuring the phone line side circuitry to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

configuring the powered side circuitry to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements;

configuring the powered side circuitry and the phone line side circuitry so that power is capable of being provided from the phone line side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards;

operating a DC holding circuit in first and second off-hook phases;

utilizing a first DC holding circuit time constant during the first phase; and

utilizing a second DC holding circuit time constant during the second phase, wherein the first time constant provides faster settling of the DC holding circuit than the second time constant.

63. The method of claim 62, further comprising operating the DC holding circuit operable in the first phase to allow for a first settling time for establishing off-hook conditions and the second phase having to allow for a second settling time after the first phase.

64. The method of claim 62, further comprising operating the DC holding circuit operable in the first phase to allow for a first settling time for establishing off-hook conditions and the second phase having to allow for a second settling time after the first phase.

65. The method of claim 62, the first time constant being at least an order of magnitude shorter than the second time constant.

66. The method of claim 62, wherein the clock signal is provided from the powered side circuitry to the phone line side circuitry through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

67. The method of claim 62, wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

68. The method of claim 62, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

70. A method of providing a communication system that may be coupled to a phone line, comprising:

coupling an isolation barrier between powered side circuitry and phone line side circuitry, the isolation barrier comprising a plurality of isolation elements;

configuring the powered side circuitry to communicate a first digital differential signal 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;

configuring the phone line side circuitry to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals, wherein at least one of the first digital differential signal and the second digital differential signal includes both data and control information;

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

configuring the powered side circuitry and the phone line side circuitry so that power is capable of being provided from the phone line side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards;

operating a DC holding circuit in first and second off-hook phases;

utilizing a first DC holding circuit time constant during the first phase; and

utilizing a second DC holding circuit time constant during the second phase, wherein the first time constant provides faster settling of the DC holding circuit than the second time constant.

71. The method of claim 70, further comprising operating the DC holding circuit operable in the first phase to allow for a first settling time for establishing off-hook conditions and the second phase having to allow for a second settling time after the first phase.

72. The method of claim 70, further comprising operating the DC holding circuit operable in the first phase to allow for a first settling time for establishing off-hook conditions and the second phase having to allow for a second settling time after the first phase.

73. The method of claim 70, the first time constant being at least an order of magnitude shorter than the second time constant.

74. The method of claim 70, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

75. The method of claim 70, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

76. A communication system, comprising:

phone line side circuitry capable of being coupled to phone lines;

powered side circuitry capable of being coupled to the phone line side circuitry through an isolation barrier comprised of a plurality of isolation elements;

a DC holding circuit within the phone line side circuitry, the DC holding circuit comprising;

at least a first circuit within the DC holding circuit, the first circuit affecting the settling time of the DC holding circuit,

at least one switchable circuit, the switchable circuit having a first state for a first phase of operation of the DC holding circuit and a second state for a second phase of operation of the DC holding circuit, the at least one switchable circuit coupled to the first circuit, and

at least one switched element selectively connectable to the first circuit by the switchable circuit, a time constant of the DC holding circuit changing depending upon the state of the at least one switchable circuit;

wherein the powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

wherein the phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

wherein the powered side circuitry is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements; and

wherein the powered side circuitry and the phone line side circuitry are configured so that power is capable of being provided from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards.

77. The communication system of claim 76, the DC holding circuit having a first time constant when the switchable circuit is configured for the first state and having a second time constant when the switchable circuit is configured for the second state, the first time constant being shorter than the second time constant.

78. The communication system of claim 76, the DC holding circuit operable in the first phase to allow for a first settling time for establishing off-hook conditions and the second phase having to allow for a second settling time after the first phase, the second settling time being slower than the first.

79. The communication system of claim 77, the first time constant being at least an order of magnitude shorter than the second time constant.

80. The communication system of claim 79, the first time constant being less than about 10 msec and the second time constant being greater than about 100 msec.

81. The communication system of claim 77, the first time constant being at least an order of magnitude shorter than the second time constant.

82. The communication system of claim 76, wherein the powered side circuitry is further configured to provide the clock signal to the phone line side circuitry through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

83. The communication system of claim 76, wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

84. The communication system of claim 76, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

85. The communication system of claim 76, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

86. A communication system, comprising:

phone line side circuitry capable of being coupled to phone lines;

powered side circuitry capable of being coupled to the phone line side circuitry through an isolation barrier comprised of a plurality of isolation elements;

a DC holding circuit within the phone line side circuitry, the DC holding circuit comprising;

at least a first circuit within the DC holding circuit, the first circuit affecting the settling time of the DC holding circuit,

at least one switchable circuit, the switchable circuit having a first state for a first phase of operation of the DC holding circuit and a second state for a second phase of operation of the DC holding circuit, the at least one switchable circuit coupled to the first circuit, and

at least one switched element selectively connectable to the first circuit by the switchable circuit, a time constant of the DC holding circuit changing depending upon the state of the at least one switchable circuit;

wherein the powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

wherein the phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

wherein the powered side circuitry is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements that is separate from the first isolation capacitor and the second isolation capacitor;

wherein the powered side circuitry and the phone line side circuitry are configured so that power is capable of being provided from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards; and

wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

87. The communication system of claim 86, the DC holding circuit having a first time constant when the switchable circuit is configured for the first state and having a second time constant when the switchable circuit is configured for the second state, the first time constant being shorter than the second time constant.

88. The communication system of claim 86, the DC holding circuit operable in the first phase to allow for a first settling time for establishing off-hook conditions and the second phase having to allow for a second settling time after the first phase, the second settling time being slower than the first.

89. The communication system of claim 87, the first time constant being at least an order of magnitude shorter than the second time constant.

90. The communication system of claim 89, the first time constant being less than about 10 msec and the second time constant being greater than about 100 msec.

91. The communication system of claim 87, the first time constant being at least an order of magnitude shorter than the second time constant.

92. The communication system of claim 86, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

93. The communication system of claim 86, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

94. A method of providing a communication system capable of being coupled to a phone line, comprising:

coupling an isolation barrier between powered side circuitry and phone line side circuitry, the isolation barrier comprising a plurality of isolation elements;

configuring the powered side circuitry to communicate a first digital differential signal 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;

configuring the phone line side circuitry to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

configuring the powered side circuitry to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements;

configuring the powered side circuitry and the phone line side circuitry so that power is capable of being provided from the phone line side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards;

forming a DC holding circuit within the phone line side circuitry, the DC holding circuit being formed with internal circuitry internal to an integrated circuit and external circuitry external to the integrated circuit;

providing a programmable circuit for switching the DC holding circuit between at least a first and second phase of operation; and

configuring the DC holding circuit to allow for the DC holding circuit to operate faster during the first phase and slower during the second phase.

95. The method of claim 94, further comprising configuring the DC holding circuit to be operable in the first phase to allow for a first settling time for establishing off-hook conditions and in the second phase to allow for a second settling time after the first phase.

96. The method of claim 95, the first time constant being at least an order of magnitude shorter than the second time constant.

97. The method of claim 94, wherein the clock signal is provided from the powered side circuitry to the phone line side circuitry through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

98. The method of claim 94, wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

99. The method of claim 94, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

100. The method of claim 94, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

101. A method of providing a communication system capable of being coupled to a phone line, comprising:

coupling an isolation barrier between powered side circuitry and phone line side circuitry, the isolation barrier comprising a plurality of isolation elements;

configuring the powered side circuitry to communicate a first digital differential signal 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;

configuring the phone line side circuitry to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals, wherein at least one of the first digital differential signal and the second digital differential signal includes both data and control information;

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

configuring the powered side circuitry and the phone line side circuitry so that power is capable of being provided from the phone line side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards;

forming a DC holding circuit within the phone line side circuitry, the DC holding circuit being formed with internal circuitry internal to an integrated circuit and external circuitry external to the integrated circuit;

providing a programmable circuit for switching the DC holding circuit between at least a first and second phase of operation; and

configuring the DC holding circuit to allow for the DC holding circuit to operate faster during the first phase and slower during the second phase.

102. The method of claim 101, further comprising configuring the DC holding circuit to be operable in the first phase to allow for a first settling time for establishing off-hook conditions and in the second phase to allow for a second settling time after the first phase.

103. The method of claim 102, the first time constant being at least an order of magnitude shorter than the second time constant.

104. The method of claim 101, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

105. The method of claim 101, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

106. A method of operating a DAA circuit, comprising:

providing phone line side circuitry capable of being coupled to phone lines;

providing powered side circuitry capable of being coupled to the phone line side circuitry through an isolation barrier comprised of a plurality of isolation elements;

providing a DC holding circuit within the phone line side circuitry;

utilizing a first time constant of the DC holding circuit during a first phase of operation of the DC holding circuit; and

utilizing a second time constant of the DC holding circuit during a second phase of operation of the DC holding circuit, settling times of the DC holding circuit being faster during the first phase than during the second;

wherein the powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

wherein the phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

wherein the powered side circuitry is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements; and

wherein the powered side circuitry and the phone line side circuitry are configured so that power is capable of being provided from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards.

107. The method of claim 106, further comprising configuring the DC holding circuit to be operable in the first phase to allow for a first settling time for establishing off-hook conditions and in the second phase to allow for a second settling time after the first phase.

108. The method of claim 107, the first time constant being at least an order of magnitude shorter than the second time constant.

109. The method of claim 106, the first time constant being at least an order of magnitude shorter than the second time constant.

110. The method of claim 106, wherein the powered side circuitry is further configured to provide the clock signal to the phone line side circuitry through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

111. The method of claim 106, wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

112. The method of claim 106, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

113. The method of claim 106, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

114. A method of operating a DAA circuit, comprising:

providing phone line side circuitry capable of being coupled to phone lines;

providing powered side circuitry capable of being coupled to the phone line side circuitry through an isolation barrier comprised of a plurality of isolation elements;

providing a DC holding circuit within the phone line side circuitry;

utilizing a first time constant of the DC holding circuit during a first phase of operation of the DC holding circuit; and

utilizing a second time constant of the DC holding circuit during a second phase of operation of the DC holding circuit, settling times of the DC holding circuit being faster during the first phase than during the second;

wherein the powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

wherein the phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

wherein the powered side circuitry is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements that is separate from the first isolation capacitor and the second isolation capacitor;

wherein the powered side circuitry and the phone line side circuitry are configured so that power is capable of being provided from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards; and

wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

115. The method of claim 114, further comprising configuring the DC holding circuit to be operable in the first phase to allow for a first settling time for establishing off-hook conditions and in the second phase to allow for a second settling time after the first phase.

116. The method of claim 115, the first time constant being at least an order of magnitude shorter than the second time constant.

117. The method of claim 114, the first time constant being at least an order of magnitude shorter than the second time constant.

118. The method of claim 114, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

119. The method of claim 114, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.