Integrated modem and line-isolation circuitry and associated method utilizing a DC termination pin to monitor line voltage

• US 6,771,696 B1
• Filed: 06/26/2000
• Issued: 08/03/2004
• Est. Priority Date: 07/23/1999
• Status: Expired due to Fees

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Huang, Yunteng, Tuttle, George T., Dupuis, Timothy J.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): MUNOZ, GUILLERMO
• Application Number:
  US09/603,022
• Time in Patent Office: 1,499 Days
• Field of Search: 375/222, 375/220, 375/258, 375/377, 379/93, 379/3, 379/9.06, 379/26.01, 379/29.07, 379/81, 379/86, 379/93.05, 379/390.04, 379/394, 379/402, 455/403, 370/463
• US Class Current: 375/222
• CPC Class Codes: H04L 25/0266 Arrangements for providing Galvanic isolation, e.g. by means of magnetic or capacitive coupling
• CPC Class Codes: H04L 25/4927 using levels matched to the quantisation levels of the channel
• CPC Class Codes: H04L 27/00 Modulated-carrier systems

Abstract

An improved modem architecture and associated method are disclosed that integrate modem and line-isolation circuitry so as to achieve modem functionality and system-side isolation functionality on a single integrated circuit. The combined modem and line isolation system has both on-hook and off-hook intrusion detection for use with parallel connected phone line connection devices. During on-hook intrusion detection, when the combined modem and line isolation system is on-hook the system can detect if other parallel connected phone line connection devices are already off-hook. During off-hook intrusion detection, when the combined modem and line isolation system is off-hook the system can detect if other parallel connected phone line connection devices are attempting to go off-hook. On-hook intrusion detection may be accomplished by monitoring the phone line voltage through a pin utilized for setting DC termination characteristics.

Claims

1. A combined modem and line-isolation system, comprising:

a line-side line-isolation integrated circuit configured to be coupled to a phone line;

a system-side line-isolation integrated circuit;

digital signal processing (DSP) circuitry included within the system-side line-isolation integrated circuit, the DSP circuitry having a modem processor for modem data and a digital processor for system-side circuitry;

a dc termination pin on the line-side line isolation integrated circuit, the line-side line-isolation integrated circuit configured to utilize the dc termination pin to provide proper dc termination characteristics to the phone line when the line-side line-isolation circuit is in an off-hook state;

circuitry coupled to the dc termination pin and configured to cause a voltage at the dc termination pin to be proportional to a voltage on the phone line when the line-isolation integrated circuit is in an on-hook state; and

circuitry within the line-side line-isolation integrated circuit coupled to the dc termination pin and configured to utilize the dc termination pin to monitor the voltage at the dc termination pin as a voltage representative of a voltage on the phone line when the line-side line-isolation integrated circuit is in an on-hook state,

wherein the line-side line-isolation integrated circuit and the system-side line-isolation integrated circuit are capable of being coupled to an isolation barrier to communicate digital information with each other through the isolation barrier.

2. The system of claim 1, wherein the isolation barrier comprises at least one capacitor.

3. The system of claim 1, further comprising at least one switch within the line-side line-isolation integrated circuit, the line-side line-isolation integrated circuit operable to receive the voltage representative of the voltage on the phone line in response to the switch changing states.

4. The system of claim 3, wherein the voltage at the dc termination pin is utilized for phone line intrusion detection.

5. The system of claim 4, wherein the phone line intrusion detection detects the status of another parallel connected phone line connection device.

6. The system of claim 1, wherein the voltage at the dc termination pin is utilized for phone line intrusion detection.

7. The system of claim 6, wherein the phone line intrusion detection detects the status of another parallel connected phone line connection device.

8. The system of claim 1, the system-side line-isolation integrated circuit further comprising a communication interface capable of connecting to an external system-side integrated circuit.

9. The system of claim 8, wherein the communication interface is operable as an asynchronous serial interface.

10. The system of claim 1, wherein the system-side line-isolation integrated circuit and the line-side line-isolation integrated circuit provide phone-line direct-access-arrangement functionality.

34. The system of claim 1, further comprising analog-to-digital conversion (ADC) circuitry within the line-side line-isolation integrate circuit coupled to the dc termination pin, the ADC circuitry configured to convert the voltage at the dc termination pin to a multiple-bit digital value representative of the phone line voltage when the line-side line-isolation integrated circuit is in an on-hook state.

11. A telephone line isolation system, comprising:

a line-side line-isolation integrated circuit, the line-side integrated circuit configured to be coupled between a phone line isolation barrier and a phone line; and

a dc termination pin on the line-side line isolation integrated circuit, the line-side line-isolation integrated circuit configured to utilize the dc termination pin to provide proper dc termination characteristics to the phone line when the line-side line-isolation circuit is in an off-hook state;

circuitry coupled to the dc termination pin and configured to cause a voltage at the dc termination pin to be proportional to a voltage on the phone line when the line-isolation integrated circuit is in an on-hook state; and

circuitry within the line-side line-isolation integrated circuit coupled to the dc termination pin and configured to utilize the dc termination pin to monitor the voltage at the dc termination pin as a voltage representative of a voltage on the phone line when the line-side line-isolation integrated circuit is at least some on-hook states.

12. The system of claim 11, further comprising at least one switch within the line-side line-isolation integrated circuit, the line-side line-isolation integrated circuit operable to receive the voltage representative of the voltage on the phone line in response to the switch changing states.

13. The system of claim 12, wherein the switch is coupled between at least two additional pins of the line-side line-isolation integrated circuit to selectively short the two additional pins together to allow the voltage at the dc termination pin to be representative of the voltage on the phone line.

14. The system of claim 13, wherein the voltage at the dc termination pin is indicative of a phone line intrusion status.

15. The system of claim 14, wherein the voltage at the dc termination pin indicates that another parallel connected phone line connection device is in an off-hook state.

16. The system of claim 14, wherein the voltage at the dc termination pin indicates that another parallel connected phone line connection device is in an on-hook state.

17. The system of claim 11, wherein the voltage at the dc termination pin indicates that another parallel connected phone line connection device is in an off-hook state.

18. The system of claim 11, wherein the voltage at the dc termination pin indicates that another parallel connected phone line connection device is in an on-hook state.

35. The system of claim 11, further comprising analog-to-digital conversion (ADC) circuitry within the line-side line-isolation integrate circuit coupled to the dc termination pin, the ADC circuitry configured to convert the voltage at the dc termination pin to a multiple-bit digital value representative of the phone line voltage when the line-side line-isolation integrated circuit is in at least some on-hook states.

19. A method for combining line-isolation and modem data processing, comprising:

providing a phone line isolation barrier comprised of at least one capacitor;

providing a system-side line-isolation integrated circuit capable of transmitting digital data across the isolation barrier and capable of receiving digital data across the isolation barrier;

providing a line-side line-isolation integrated circuit capable of transmitting digital data across the isolation barrier and capable of receiving digital data across the isolation barrier;

utilizing a dc termination pin to provide proper dc termination characteristics to the phone line when the line-side line-isolation circuit is in an off-hook state;

when the line-side line-isolation circuit is in an on-hook state, causing a voltage at the dc termination pin to be proportional to a voltage on the phone line and monitoring the voltage at the dc termination pin as being a voltage representative of a voltage on the phone line;

communicating digital information between the line-side line-isolation integrated circuit and the system-side line-isolation integrated circuit through at least one capacitor of the isolation barrier;

processing the digital data transmitted or received across the isolation barrier with a digital processor within the system-side line-isolation integrated circuit; and

also processing the digital data transmitted or received across the isolation barrier with a modem processor within the system-side line-isolation integrated circuit.

20. The method of claim 19 wherein the communicating digital information includes communicating a digital signal representative of the voltage on the phone line during at least some periods when the line-side line isolation integrated circuit is in an on-hook state.

21. The method of claim 20, further comprising changing the state of at least one switch within the line-side line-isolation integrated circuit to receive the voltage representative of the voltage on the phone line at the dc termination pin.

22. The method of claim 20, wherein the voltage at the dc termination pin is indicative of a phone line intrusion status.

23. The method of claim 22, wherein the voltage at the dc termination pin indicates that another parallel connected phone line connection device is in an off-hook state.

24. The method of claim 22, wherein the voltage at the dc termination pin indicates that another parallel connected phone line connection device is in an on-hook state.

25. The method of claim 19, wherein the voltage at the dc termination pin indicates that another parallel connected phone line connection device is in an off-hook state.

26. The method of claim 19, wherein the voltage at the dc termination pin indicates that another parallel connected phone line connection device is in an on-hook state.

36. The method of claim 19, further comprising converting the voltage at the dc termination pin to a multiple-bit digital value representative of the phone line voltage when the line-side line-isolation integrated circuit is in at least some on-hook states.

27. A method of operating a line-side integrated circuit, the line-side integrated circuit capable of coupling a phone line to phone line isolation barrier, the phone line isolation barrier having at least one isolation capacitor, the method comprising:

providing a dc termination pin on the line-side line isolation integrated circuit through which proper dc termination characteristics are provided to a phone line when the line-side line-isolation circuit is in an off-hook state; and

when the line-side line-isolation circuit is in an on-hook state, causing a voltage at the dc termination pin to be proportional to a voltage on the phone line and monitoring the voltage at the dc termination pin as being a voltage representative of a voltage on the phone line.

28. The method of claim 27, further comprising changing the state of at least one switch within the line-side line-isolation integrated circuit to receive the voltage representative of the voltage on the phone line at the dc termination pin.

29. The method of claim 28, wherein the switch shorts at least two additional pins of the line-side line-isolation integrated circuit so that the dc termination pin receives the voltage representative of the voltage on the phone line.

30. The method of claim 28, wherein the voltage at the dc termination pin indicates that another parallel connected phone line connection device is in an off-hook state.

31. The method of claim 28, wherein the voltage at the dc termination pin indicates that another parallel connected phone line connection device is in an on-hook state.

32. The method of claim 27, wherein the voltage at the dc termination pin indicates that another parallel connected phone line connection device is in an off-hook state.

33. The method of claim 27, wherein the voltage at the dc termination pin indicates that another parallel connected phone line connection device is in an on-hook state.

37. The method of claim 27, further comprising converting the voltage at the dc termination pin to a multiple-bit digital value representative of the phone line voltage when the line-side line-isolation integrated circuit is in at least some on-hook states.