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

• US 7,301,995 B2
• Filed: 02/17/2004
• Issued: 11/27/2007
• 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:
  US10/780,219
• Publication Number:
  US 20040161024A1
• Time in Patent Office: 1,379 Days
• Field of Search: 375/220, 375/222, 375/285, 375/219, 375/257, 375/259, 375/359, 379/399.02, 379/412, 379/413
• 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. A method for communicating with phone lines across an isolation barrier that comprises a plurality of isolation elements, the method comprising:

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

communicating said encoded digital differential signal from phone line side circuitry to powered side circuitry across at least two of the isolation elements of said isolation barrier, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor, wherein bidirectional communication exists through the first and second isolation capacitors;

providing a clock signal from the powered side circuitry to the phone line side circuitry through at least one of the plurality of isolation elements; and

providing power from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards.

2. The method of claim 1, wherein said control data comprises phone line status information.

3. The method of claim 1, wherein the encoded digital differential signal includes both data information and control information.

4. The method of claim 1, further comprising providing a clock signal from the powered side circuitry 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.

5. The method of claim 1, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

6. The method of claim 1, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

7. A method for communicating with phone lines across an isolation barrier that comprises a plurality of isolation elements, the method comprising:

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

communicating said encoded digital differential signal from phone line side circuitry to powered side circuitry across at least two of the isolation elements of said isolation barrier, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor, wherein bidirectional communication exists through the first and second isolation capacitors;

providing a clock signal from the powered side circuitry 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; and

providing power from the powered side circuitry to the phone line side circuitry o generate at least one power supply within the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards;

wherein the encoded digital differential signal includes both data information and control information.

8. The method of claim 7, wherein said control data comprises phone line status information.

9. The method of claim 7, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

10. The method of claim 7, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

11. A method for communicating with phone lines across an isolation barrier that comprises a plurality of isolation elements, the method comprising:

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

communicating said digital data stream as a digital differential signal from bi-directional connections on phone line side circuitry to bi-directional connections on powered side circuitry across at least two of the isolation elements of said isolation barrier, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor, wherein bi-directional communication occurs across the first and second isolation capacitors;

providing a clock signal from the powered side circuitry to the phone line side circuitry through at least one of the plurality of isolation elements; and

providing power from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards.

12. The method of claim 11, further comprising:

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

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

13. The method of claim 11, further comprising encoding said digital data stream prior to said communicating step.

14. The method of claim 11, wherein the digital differential signal includes both data information and control information.

15. The method of claim 11, further comprising providing a clock signal from the powered side circuitry 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.

16. The method of claim 11, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

17. The method of claim 11, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

18. A method for communicating with phone lines across an isolation barrier that comprises a plurality of isolation elements, the method comprising:

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

communicating said digital data stream as a digital differential signal from bi-directional connections on phone line side circuitry to bi-directional connections on powered side circuitry across at least two of the isolation elements of said isolation baffler, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

providing a clock signal from the powered side circuitry 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; and

providing power from the powered side circuitry to the phone line side circuitry to generate at least one power supply within the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards;

wherein the digital differential signal includes both data information and control information.

19. The method of claim 18, further comprising:

communicating a digital bit stream across said isolation barrier from said powered side circuitry to said phone line side circuitry through said at least one of the plurality of isolation elements that is separate from the first isolation capacitor and the second isolation capacitor; and

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

20. The method of claim 18, further comprising encoding said digital data stream prior to said communicating step.

21. The method of claim 18, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

22. The method of claim 18, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

23. A method for communicating with phone lines from a user end of the phone lines across an isolation barrier that comprises a plurality of isolation elements, the method comprising:

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

communicating said encoded digital differential signal from user end powered side circuitry to user end phone line side circuitry across at least two of the isolation elements of said isolation barrier, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor, wherein bidirectional communication exists through the first and second isolation capacitors;

providing a clock signal from the user end powered side circuitry to the user end phone line side circuitry through at least one of the plurality of isolation elements; and

providing power from the user end powered side circuitry to the user end phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards.

24. The method of claim 23, wherein the encoded digital differential signal includes both data information and control information.

25. The method of claim 23, further comprising providing a clock signal from the user end powered side circuitry to the user end 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.

26. The method of claim 23, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

27. The method of claim 23, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.