Common-mode suppression circuit for emission reduction

1 . A network device comprising:

an interface coupled between an Ethernet physical layer (PHY) module and a network connector, the interface comprising at least one pair of pins coupled to output connections of the Ethernet physical layer (PHY), a direct current (DC) blocking capacitor coupled to each pin, and a common-mode suppression amplifier coupled between the paired pins.

2 . The network device according to claim 1 further comprising:

the common-mode suppression amplifier coupled to the paired pins between the DC blocking capacitors and the Ethernet physical layer (PHY) output connections.

3 . The network device according to claim 1 further comprising:

the DC blocking capacitors coupled to the paired pins between the Ethernet physical layer (PHY) output connections and the common-mode suppression amplifier.

4 . The network device according to claim 1 further comprising:

a control device coupled to the common-mode suppression amplifier and the Ethernet physical layer (PHY) that controls the common-mode suppression amplifier to enable the Ethernet physical layer (PHY) to set a direct current (DC) value of common-mode voltage and suppress high-frequency common-mode signal components on the paired pins.

5 . The network device according to claim 1 further comprising:

a control device coupled to the common-mode suppression amplifier and the Ethernet physical layer (PHY) that samples common-mode voltage at the Ethernet physical layer (PHY) output connections at regular intervals and adjusts input to the common-mode suppression amplifier to approximate the common-mode voltage.

6 . The network device according to claim 1 further comprising:

a control device direct-current (dc)-coupled to the Ethernet physical layer (PHY) that adjusts a control signal to the common-mode suppression amplifier and is adapted to adjust common-mode of the common-mode amplifier at an amplitude that avoids overdriving.

7 . The network device according to claim 1 further comprising:

a control device alternating-current (ac)-coupled to the Ethernet physical layer (PHY) that adjusts a control signal to the common-mode suppression amplifier and is adapted to suppress common-mode noise.

8 . The network device according to claim 1 further comprising:

a control device coupled to the Ethernet physical layer (PHY) that sets a common-mode direct current (dc) voltage and suppresses common-mode noise above a designated frequency.

9 . The network device according to claim 1 further comprising:

the common-mode suppression amplifier is separated from an integrated circuit containing the Ethernet physical layer (PHY).

10 . The network device according to claim 1 further comprising:

the interface coupled between the Ethernet physical layer (PHY) module, the network connector, and a T connect integrated circuit.

11 . The network device according to claim 1 further comprising:

the common-mode suppression amplifier comprising a bandpass filter.

12 . The network device according to claim 1 further comprising:

the common-mode suppression amplifier comprising a lowpass filter.

13 . The network device according to claim 1 further comprising:

the paired pins coupled to the interface in a configuration adapted to sense common-mode noise at input terminals to the network connector.

14 . A network device comprising:

an interface coupled between an Ethernet physical layer (PHY) module and a network connector operative at a voltage substantially higher than the PHY module, the interface configured to pass signals from a relatively high voltage technology at the network connector to a relatively low voltage technology at the PHY module, the interface adapted to sense common-mode noise in a high voltage technology region adjacent to the network connector and adapted to suppress the common-mode noise in a low voltage technology region adjacent to the PHY module.

15 . A network device comprising:

an interface coupled between an Ethernet physical layer (PHY) module and a network connector operative at a voltage substantially higher than the PHY module, the interface configured to pass signals from a relatively high voltage technology at the network connector to a relatively low voltage technology at the PHY module, the interface adapted to sense common-mode noise in a high voltage technology region adjacent to the network connector, the high voltage technology region comprising a common-mode suppression amplifier adapted to suppress the common-mode noise in a low voltage technology region adjacent to the PHY module whereby signals are passed to the common-mode suppression amplifier through a capacitor fabricated on a high-voltage die.

16 . The network device according to claim 15 further comprising:

the low voltage technology region comprising an integrated circuit configured in fine-line geometries.

17 . The network device according to claim 15 further comprising:

a common-mode suppression amplifier fabricated in the low voltage technology region and adapted to suppress the common-mode noise.

18 . The network device according to claim 15 further comprising:

the interface comprising at least one pair of pins coupled to output connections of the Ethernet physical layer (PHY) and a common-mode suppression amplifier coupled between the paired pins.

19 . The network device according to claim 18 further comprising:

a control device coupled to the common-mode suppression amplifier and the Ethernet physical layer (PHY) that controls the common-mode suppression amplifier to enable the Ethernet physical layer (PHY) to set a direct current (DC) value of common-mode voltage and suppress high-frequency common-mode signal components on the paired pins.

20 . The network device according to claim 18 further comprising:

a control device coupled to the common-mode suppression amplifier and the Ethernet physical layer (PHY) that samples common-mode voltage at the Ethernet physical layer (PHY) output connections at regular intervals and adjusts input to the common-mode suppression amplifier to approximate the common-mode voltage.

21 . A method of operating a network device comprising:

passing signals from a relatively high voltage technology at a network connector to a relatively low voltage technology at an Ethernet physical layer (PHY) module;

sensing common-mode noise in a high voltage technology region adjacent to the network connector; and

suppressing the common-mode noise in a low voltage technology region adjacent to the PHY module.

22 . The method according to claim 21 further comprising:

fabricating a common-mode suppression amplifier in the low voltage technology region; and

suppressing the common-mode noise using the common-mode suppression amplifier.

23 . The method according to claim 21 further comprising:

controlling common-mode suppression to enable the Ethernet physical layer (PHY) to set a direct current (DC) value of common-mode voltage and suppress high-frequency common-mode signal components.

24 . The method according to claim 21 further comprising:

sampling common-mode voltage at regular intervals; and

adjusting common-mode suppression to approximate the common-mode voltage.

25 . The method according to claim 21 further comprising:

setting common-mode direct current (dc) voltage; and

suppressing common-mode noise above a designated frequency.

26 . The method according to claim 21 further comprising:

sensing common-mode noise at input terminals to the network connector.

27 . A network device comprising:

a network connector adapted to physically couple the network device to a network and receive both a power signal and a data signal through the coupled network;

an integrated circuit coupled to the network connector and comprising at least one functional element, the at least one functional element comprising an Ethernet physical layer (PHY) module; and

an interface coupled between the integrated circuit and the network connector and configured to pass signals from a relatively high voltage technology at the network connector to a relatively low voltage technology at the integrated circuit, the interface adapted to sense common-mode noise at the network connector and adapted to suppress the common-mode noise in the integrated circuit.

28 . The network device according to claim 27 further comprising:

the interface comprising at least one pair of pins coupled to output connections of the Ethernet physical layer (PHY), a direct current (DC) blocking capacitor coupled to each pin, and a common-mode suppression amplifier coupled between the paired pins.

29 . The network device according to claim 28 further comprising:

a control device coupled to the common-mode suppression amplifier and the Ethernet physical layer (PHY) that controls the common-mode suppression amplifier to enable the Ethernet physical layer (PHY) to set a direct current (DC) value of common-mode voltage and suppress high-frequency common-mode signal components on the paired pins.