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

• US 7,463,675 B2
• Filed: 04/05/2006
• Issued: 12/09/2008
• 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): PHU, PHUONG M
• Application Number:
  US11/398,090
• Publication Number:
  US 20060215771A1
• Time in Patent Office: 979 Days
• Field of Search: 375/220, 375/222, 375/219, 375/257, 375/259, 375/359, 379/412, 379/405, 379/413, 379/399, 379/377, 379/399.02
• 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 transmitted across an isolation barrier;

the phone line side circuitry operable to communicate digitally with the powered side circuitry across said isolation barrier, the phone line side circuitry comprising a digital to analog converter to convert digital information contained in the digital data stream to analog form for transmission to the phone line connection; and

encode 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 powered side circuitry has a communication interface that is capable of being coupled to an external device.

5. 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.

6. The digital direct access arrangement circuitry of claim 1, wherein the encode circuitry is contained within the powered side circuitry so that the encoded digital signal is generated for transmission from the powered side circuitry to the phone line side circuitry across said isolation barrier.

7. The digital direct access arrangement circuitry of claim 1, wherein the encode circuitry is contained within the phone line side circuitry so that the encoded digital signal is generated for transmission from the phone line side circuitry to the powered line side circuitry across said isolation barrier.