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

• US 7,200,167 B2
• Filed: 04/22/2002
• Issued: 04/03/2007
• 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:
  US10/127,285
• Publication Number:
  US 20020154702A1
• Time in Patent Office: 1,807 Days
• Field of Search: 375/285, 375/222, 375/220, 375/219, 375/257, 375/259, 375/359, 375/377, 379/412, 379/405, 379/413, 379/399, 379/377, 379/399.01, 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. Powered side circuitry for digital direct access arrangement circuitry for terminating a phone line connection at a user end of an analog phone line, comprising:

a communication interface within said powered side circuitry, said communication interface having at least one data input or data output capable of being coupled to an external user end device;

an isolation interface within said powered side circuitry and coupled to said communication interface, said 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,

wherein the isolation interface is configured to transmit the encoded digital signal in a first direction across the user end isolation barrier and is configured to receive information provided in an opposite direction across the isolation barrier from the user end phone line side circuitry,

wherein information within the digital data stream is converted to an analog form within the user end phone line side circuitry prior to transmission on the analog phone line.

2. The powered side circuitry of claim 1, wherein said encoded digital signal comprises framing data added to said digital data stream for data synchronization within said user end phone line side circuitry.

3. The powered side circuitry of claim 1, 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.

4. The powered side circuitry of claim 1, wherein signals communicated through said communication interface comprises digital data signals, control signals and phone line status signals.

5. The powered side circuitry of claim 4, wherein said communication interface comprises a digital serial port interface within which said at least one data input or data output is located.

6. The powered side circuitry of claim 1, further comprising an oversampled delta-sigma modulator coupled to receive base-band digital data signals from said external user end device through said communication interface and to convert said base-band digital data signals to a digital data stream in a pulse density modulation format.

7. The powered side circuitry of claim 1, further comprising decode circuitry within said isolation interface, said decode circuitry capable of being coupled to an encoded digital signal received from said user end phone line side circuitry to generate a decoded digital signal.

8. The powered side circuitry of claim 7, wherein said decoded digital signal comprises a digital data stream in a pulse density modulation format, and further comprising a digital filter within said isolation interface and coupled to said digital data stream to generate base-band digital data signals.

9. A method for communicating with an analog phone line from a user end of the analog phone line, 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 a user end isolation barrier from user end powered side circuitry to user end phone line side circuitry through an isolation interface within the powered side circuitry that is configured to be coupled to an isolation barrier,

wherein the isolation interface is configured to transmit the encoded digital signal in a first direction across the user end isolation barrier and is configured to receive information provided in an opposite direction across the isolation barrier from the user end phone line side circuitry,

wherein information within the digital data signal is converted to an analog form within the user end phone line side circuitry prior to transmission on the analog phone line.

10. The method of claim 9, wherein said generating step further comprises adding synchronization framing information to said digital data stream.

11. The method of claim 9, wherein said generating step comprises formatting said digital data stream so that a clock signal is recoverable from said encoded digital signal.

12. The method of claim 11, wherein said generating step further comprises adding synchronization framing information to said digital data stream.

13. The method of claim 12, wherein said user end isolation barrier comprises one or more capacitors which provide isolation between said user end powered side circuitry and said user end phone line side circuitry.

14. A method for communicating with an analog phone line from a user end of the analog phone line, 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, wherein information within the digital data stream is converted to an analog form within the user end phone line side circuitry prior to transmission on the analog phone line.

15. The method of claim 14, wherein said user end isolation barrier comprises one or more capacitors which provide isolation between said user end powered side circuitry and said user end phone line side circuitry.

16. The method of claim 14, further comprising encoding said digital data stream prior to said communicating step.