Power over Ethernet with isolation

1. A circuit comprising:

an application device comprising an Ethernet Physical layer (PHY) and a port for interfacing to a powered device;

an interface configured for coupling a network line to the powered device via the application device and communicating operating power and data to the powered device from the network line; and

an isolator coupled between the application device and the powered device isolating the application device and the interface referenced to a line reference from the powered device referenced to a device reference, the application device referenced to the line reference.

2. The circuit according to claim 1 further comprising:

the application device and the interface configured to an Institute of Electrical and Electronics Engineers (IEEE) 802.3 Power over Ethernet standard.

3. The circuit according to claim 1 further comprising:

the application device comprising an application processor and the Ethernet Physical layer (PHY) coupled between the network line and the application processor; and

the interface comprising a solid-state transformer line interface that connects the Ethernet PHY to the network line and transfers operating power and data to the powered device in absence of networking line transformers.

4. The circuit according to claim 1 further comprising:

the application device comprising an application processor and the Ethernet Physical layer (PHY) coupled between the network line to the application processor; and

a solid-state transformer line interface comprising a rectification and electromagnetic interference (EMI) protection circuit coupled to the network line, first and second power feed elements coupled to the rectification and EMI protection circuit, a powered device (PD) controller coupled between the first and second power feed elements, and a direct current-to-direct current (DC/DC) converter, the solid-state transformer line interface transferring the line reference through the DC/DC converter to a ground reference of the application device through a surge resistance, referencing the application device and the solid-state transformer line interface to a common ground.

5. The circuit according to claim 4 further comprising:

a surge resistor coupled between the interface and the application device that forms a low impedance ground return path for electromagnetic interference (EMI) noise under normal operation; and

the solid-state transformer line interface further comprising a cross-over detect circuit that responds to surge/lightning events by increasing the surge resistance to open circuit, increasing impedance from the device reference to the line reference.

6. The circuit according to claim 1 further comprising:

the isolator is a digital isolator comprising a capacitively-coupled interconnect that capacitively transmits a signal from the application device to the powered device whereby optical coupling between the device reference and the line reference can be omitted.

7. The circuit according to claim 1 further comprising:

the isolator is a digital isolator comprising an inductively-coupled interconnect that inductively transmits a signal from the application device to the powered device whereby optical coupling between the device reference and the line reference can be omitted.

8. The circuit according to claim 1 further comprising:

the isolator is a digital and power isolator comprising an interconnect and a power transformer.

9. The circuit according to claim 1 further comprising:

the interface comprising a solid-state transformer line interface that connects the Ethernet PHY to the network line and transfers operating power and data to the powered device in absence of networking line transformers.

10. The circuit according to claim 1 further comprising:

the port comprises a digital port.

11. The circuit according to claim 1 further comprising:

the port comprises a Universal Serial Bus (USB) port or a RETMA Standard (RS)-232 port.

12. The circuit according to claim 1 further comprising:

the application device comprising an application processor and the Ethernet Physical layer (PHY) coupled between the network line and the application processor; and

a Media Independent Interface (MII) coupling the Ethernet PHY to the application processor operative as a Media Access Controller (MAC) device.

13. The circuit according to claim 1 further comprising:

a Media Independent Interface (MII) coupling the Ethernet PHY to an application processor operative as a Media Access Controller (MAC) device in the powered device, the MII on an isolation boundary between distributed power and the powered device.

14. A system comprising:

a powered device;

a line connector configured for coupling to a network line;

an application device comprising an Ethernet Physical layer (PHY) and a port for interfacing to the powered device;

an interface configured for coupling the network line via the line connector to the powered device via the application device and communicating operating power and data to the powered device from the network line; and

an isolator coupled between the application device and the powered device isolating the application device and the interface referenced to a line reference from the powered device referenced to a device reference, the application device referenced to the line reference.

15. The system according to claim 14 further comprising:

the powered device comprising a device selected from a group consisting of a Voice-over-Internet-Protocol (VoIP) telephone, an Internet Protocol (IP) telephone, a wireless Local-Area-Network (LAN) Access Point, a security camera, a Web camera (webcam), an Analog Telephone Adapter (ADA), a Point-of-Sale (PoS) terminal, an Ethernet hub, a computer, and an appliance; and

the application device and the interface configured to an Institute of Electrical and Electronics Engineers (IEEE) 802.3 Power over Ethernet standard.

16. The system according to claim 14 further comprising:

a power source coupled to the network line;

the line connector comprising a Registered Jack (RJ)-45 connector; and

the network line configured as two wire pairs coupled to the RJ-45 connector.

17. The system according to claim 14 further comprising:

the application device comprising an application processor and the Ethernet Physical layer (PHY) coupled between the network line to the application processor; and

the interface comprising a solid-state transformer line interface that connects the Ethernet PHY to the network line and transfers operating power and data to the powered device in absence of networking line transformers.

18. The system according to claim 14 further comprising:

the application device comprising an application processor and the Ethernet Physical layer (PHY) coupled between the network line to the application processor; and

a solid-state transformer line interface comprising a rectification and electromagnetic interference (EMI) protection circuit coupled to the network line, first and second power feed elements coupled to the rectification and EMI protection circuit, a powered device (PD) controller coupled between the first and second power feed elements, and a direct current-to-direct current (DC/DC) converter, the solid-state transformer line interface transferring the line reference through the DC/DC converter to a ground reference of the application device through a surge resistance, referencing the application device and the solid-state transformer line interface to be referenced to a common ground.

19. The system according to claim 18 further comprising:

a transformer comprising first and second windings, the first winding coupled to the interface and the second winding coupled to the application device;

a surge resistor coupled between the interface and the application device that forms a low impedance ground return path for electromagnetic interference (EMI) noise under normal operation;

a diode coupled between the transformer second winding and the application device;

a low dropout regulator coupled between the diode and the application device; and

the solid-state transformer line interface further comprising a cross-over detect circuit that responds to surge/lightning events by increasing the surge resistance to open circuit, increasing impedance from the device reference to the line reference.

20. The system according to claim 14 further comprising:

the isolator is a digital isolator comprising a capacitively-coupled interconnect that capacitively transmits a signal from the application device to the powered device whereby optical coupling between the device reference and the line reference can be omitted.

21. The system according to claim 14 further comprising:

the isolator is a digital isolator comprising an inductively-coupled interconnect that inductively transmits a signal from the application device to the powered device whereby optical coupling between the device reference and the line reference can be omitted.

22. The system according to claim 14 further comprising:

the isolator is a digital and power isolator comprising an interconnect and a power transformer.

23. The system according to claim 14 further comprising:

the interface comprising a solid-state transformer line interface that connects the Ethernet PHY to the network line and transfers operating power and data to the powered device in absence of networking line transformers.

24. The system according to claim 14 further comprising:

the port comprises a digital port.

25. The system according to claim 14 further comprising:

the port comprises a Universal Serial Bus (USB) port or a RETMA Standard (RS)-232 port.

26. The system according to claim 14 further comprising:

the application device comprising an application processor and the Ethernet Physical layer (PHY) coupled between the network line to the application processor; and

a Media Independent Interface (MII) coupling the Ethernet PHY to the application processor operative as a Media Access Controller (MAC) device.

27. The system according to claim 14 further comprising:

a Media Independent Interface (MII) coupling the Ethernet PHY to an application processor operative as a Media Access Controller (MAC) device in the powered device, the MII on an isolation boundary between distributed power and the powered device.

28. A method for isolating a powered device on a network comprising:

communicating operating power and data to a powered device from a network line;

referencing the network line to a line reference;

referencing the powered device to a device reference that can be different from the line reference;

referencing an Ethernet Physical layer (PHY) to the line reference;

isolating the powered device from the network line; and

positioning an isolation boundary between distributed power and the powered device at a digital port coupled to the powered device.

29. The method according to claim 28 further comprising:

communicating operating power and data in compliance with an Institute of Electrical and Electronics Engineers (IEEE) 802.3 Power over Ethernet standard.

30. The method according to claim 28 further comprising:

transferring operating power and data to the powered device in absence of networking line transformers.

31. The method according to claim 28 further comprising:

transferring the line reference through a surge resistance that forms a low impedance ground return path for electromagnetic interference (EMI) noise under normal operation; and

responding to surge/lightning events by increasing the surge resistance to open circuit, increasing impedance from the device reference to the line reference.

32. The method according to claim 28 further comprising:

isolating the powered device from the network line using a capacitively-coupled interconnect that capacitively transmits a signal from the application device to the powered device whereby optical coupling between the device reference and the line reference can be omitted.

33. The method according to claim 28 further comprising:

isolating the powered device from the network line using an inductively-coupled interconnect that inductively transmits a signal from the application device to the powered device whereby optical coupling between the device reference and the line reference can be omitted.

34. The method according to claim 28 further comprising:

positioning the isolation boundary between distributed power and the powered device at a digital port comprising a Universal Serial Bus (USB) port or a RETMA Standard (RS)-232 port.