Extended feedback circuit employing capacitive coupling and sampled data filters

A network interface circuit for providing voltage isolation between a network coupled to a first side of said circuit and equipment coupled to a second side of said circuit, said circuit comprising:

• a receive data path for providing a path for data from said network to said equipment;
• a transmit data path for providing a path for data from said equipment to said network;
• a first pair of capacitive couplers in said receive data path;
• a second pair of capacitive couplers in said transmit data path;
• a Σ/Δ analog-to-digital converter on said first side of said capacitive couplers in said receive data path;
• a Σ/Δ digital-to-analog converter on said first side of said capacitive couplers in said transmit data path;
• a first differential driver in said receive data path coupled between said Σ/Δ analog-to-digital converter and said first capacitive coupler;
• a first differential receiver coupled on said second side of said receive path capacitive couplers;
• a second differential driver coupled on said second side of said transmit path capacitive couplers;
• and
• a second differential receiver coupled between said transmit path capacitive coupler and said Σ/Δ digital-analog converter.

A network interface circuit for providing voltage isolation and impedance matching between a network and equipment coupled to said network through said network interface circuit comprising:

• a receive data path for coupling data from said network to said equipment;
• a transmit data path for coupling data from said equipment to said network;
• a Σ/Δ analog-to-digital converter coupled to said network in said receive data path;
• a first capacitive coupler coupled in said receive data path to receive data from said Σ/Δ analog-to-digital converter;
• a digital transfer function circuit coupled between said first capacitive coupler and said equipment;
• a digital summing circuit coupled to add an output from said digital transfer function circuit to a transmit signal from said equipment;
• and
• an extended feedback circuit coupled between an output of said digital summing circuit and said digital transfer function circuit;
• wherein a gain of said digital feedback circuit is scalable to set an output impedance substantially matching a load impedance of said network.

A method for providing voltage isolation and impedance matching between a network and equipment coupled to said network, said method comprising the steps of:

• converting analog data received from said network to Σ/Δ data;
• sending said Σ/Δ data received from said network across a first capacitive coupling to said equipment;
• transmitting Σ/Δ data transmitted from said equipment across a second capacitive coupling;
• converting data transmitted said Σ/Δ data transmitted from said equipment to analog data;
• filtering and adjusting the gain of said data received from said network;
• adding said filtered and gain adjusted data received from said network to said data transmitted from said equipment to form a feedback signal;
• amplifying said feedback signal to set an output impedance substantially matching a load impedance of said network;
• and
• feeding back said amplified feedback signal into said data received from said network.

A method for providing voltage isolation and impedance matching between a network and equipment coupled to said network, said method comprising the steps of:

• converting analog data received from said network to Σ/Δ data;
• sending said Σ/Δ data received network across a first high voltage isolation coupling to said equipment;
• transmitting Σ/Δ data transmitted from said equipment across a second high voltage isolation coupling;
• converting data transmitted said Σ/Δ data transmitted from said equipment to analog data;
• filtering and adjusting the gain of said data received from said network;
• adding said filtered and gain adjusted data received from said network to said data transmitted from said equipment to form a feedback signal;
• amplifying said feedback signal to set an output impedance substantially matching a load impedance of said network;
• and
• feeding back said amplified feedback signal into said data received from said network.