Method and apparatus for transmitting NRZ data signals across an isolation barrier disposed in an interface between adjacent devices on a bus

A method for transmitting an NRZ data signal across an interface comprising an isolation barrier disposed between a first device and a second device interconnected via a bus, the method comprising the steps of:

• differentiating the data signal with a signal differentiator responsive to the clock signal to produce a differentiated signal;
• supplying the data signal as a first input to a driver comprising a tri-state gate;
• supplying the differentiated signal as a second input to the tri-state gate to enable the tri-state gate when the differentiated signal is high;
• applying a bias voltage to an output of the tri-state gate to derive as output from the tri-state gate a transmission signal comprising
• (1) an intermediate transmission signal corresponding to the voltage bias when the tri-state gate is disabled,
• (2) a high transmission signal when the tri-state gate is enabled and the first input to the tri-state gate is high, and
• (3) a low transmission signal when the tri-state gate is enabled and the first input to the tri-state gate is low;
• transmitting the transmission signal derived from the output of the tri-state gate from the first device through the isolation barrier to the second device;
• and
• supplying the transmission signal to a Schmidt trigger to derive as output from the Schmidt trigger a reconstituted data signal corresponding to the data signal.

A method for transmitting an NRZ data signal across an interface comprising an isolation barrier disposed between a first device and a second device interconnected via a bus, the method comprising the steps of:

• synchronizing the data signal with a clock signal;
• supplying the synchronized data signal to a flip-flop responsive to the clock signal to output a delayed synchronized data signal delayed by one clock period;
• supplying the synchronized data signal as a first input to an exclusive OR gate;
• supplying the delayed synchronized data signal as a second input to the exclusive OR gate to output a differentiated signal;
• supplying the synchronized data signal as a first input to a driver comprising a tri-state gate;
• supplying the differentiated signal as a second input to the tri-state gate to enable the tri-state gate when the differentiated signal is high;
• applying a bias voltage to an output of the tri-state gate to derive as output from the tri-state gate a first transmission signal comprising
• (1) an intermediate transmission signal corresponding to the bias voltage when the tri-state gate is disabled,
• (2) a high transmission signal when the tri-state gate is enabled and the first input to the tri-state gate is high, and
• (3) a low transmission signal when the tri-state gate is enabled and the first input to the tri-state gate is low;
• transmitting the first transmission signal derived from the output of the tri-state gate from the first device to the isolation barrier to generate as output from the isolation barrier a second transmission signal electrically isolated from the first transmission signal;
• and
• transmitting the second transmission signal to a Schmidt trigger having two thresholds to derive as output from the Schmidt trigger a reconstituted data signal corresponding to the synchronized data signal, wherein the bias voltage applied to the output of the tri-state gate sets a DC level of the first and second transmission signals around which a voltage difference between the thresholds of the Schmidt trigger is centered.

An apparatus for transmitting an NRZ data signal across an interface between two devices interconnected via a bus, the apparatus comprising:

• a signal differentiator responsive to a clock signal for receiving the data signal and outputting a differentiated signal;
• a driver comprising a tri-state gate having as a first input the data signal, the tri-state gate further having as a second input the differentiated signal for enabling the tri-gate when the differentiated signal is high;
• a bias voltage applied to an output of the tri-state gate to derive as output from the tri-state gate a transmission signal for transmission via the bus across the interface between the two devices;
• and
• an electronic component for receiving the transmission signal and outputting a reconstituted data signal comprising
• (1) a high data signal when the input to the electronic component reaches a value substantially above the voltage bias, and
• (2) a low data signal when the input to the electronic component reaches a value substantially below the voltage bias.

An apparatus for transmitting an NRZ data signal across an interface comprising an isolation barrier disposed between a first device and a second device interconnected via a bus, the apparatus comprising:

• a first flip-flop responsive to a clock signal for receiving the data signal and outputting a synchronized data signal;
• a second flip-flop responsive to the clock signal for receiving the synchronized data signal and outputting a delayed synchronized data signal delayed by one clock period;
• an exclusive OR gate for receiving as input the delayed synchronized data signal and the synchronized data signal and outputting a differentiated signal;
• a tri-state gate for receiving as a first input the synchronized data signal and receiving as a second input the differentiated signal, the differentiated signal enabling the tri-state gate when the differentiated signal is high;
• a bias voltage applied to an output of the tri-state gate for outputting a first transmission signal comprising
• (1) an intermediate transmission signal corresponding to the bias voltage when the tri-state gate is disabled,
• (2) a high transmission signal when the tri-state gate is enabled and the first input to the tri-state gate is high, and
• (3) a low transmission signal when the tri-state gate is enabled and the first input to the tri-state gate is low;
• a first blocking capacitor disposed in the bus between the first device and the isolation barrier;
• a first resistor disposed in the bus between the first blocking capacitor and the isolation barrier;
• the isolation barrier for receiving the first transmission signal and outputting a second transmission signal electrically isolated from the first transmission signal;
• a second resistor disposed in the bus between the isolation barrier and the second device;
• a second blocking capacitor disposed in the bus between the second resistor and the second device;
• and
• a Schmidt trigger for receiving as input the second transmission signal and outputting a reconstituted data signal corresponding to the synchronized data signal.

A method for transmitting an NRZ data signal across an interface between two devices interconnected via a bus, the method comprising the steps of:

• differentiating the data signal with a signal differentiator responsive to a clock signal to produce a differentiated signal having a first state and a second state;
• supplying the data signal as a first input to a driver comprising a tri-state gate;
• supplying the differentiated signal as a second input to the tri-state gate to enable the tri-state gate when the differentiated signal is in the first state;
• applying a bias voltage to an output of the tri-state gate to derive as output from the tri-state gate a transmission signal for transmission across the interface;
• transmitting the transmission signal across the interface between the two devices;
• and
• supplying the transmission signal as input to an electronic component having as output a reconstituted data signal comprising
• (1) a first signal corresponding to a first logic state when the input to the electronic component reaches a value substantially above the voltage bias, and
• (1) a second signal corresponding to a second logic state when the input to the electronic component reaches a value substantially below the voltage bias.