Patent ID: 7236004

Claim:
A reference voltage circuit for a differential interface, comprising: a first reference voltage source configured to provide a reference swing voltage; a second reference voltage source configured to provide a reference offset voltage; a first differential amplifier coupled to receive the reference swing voltage and a first feedback voltage, the first differential amplifier configured to provide a p-bias voltage responsive to the reference swing voltage and the first feedback voltage; a second differential amplifier coupled to receive the reference offset voltage and a second feedback voltage, the second differential amplifier configured to provide an n-bias voltage responsive to the reference offset voltage and the second feedback voltage; a first reference input/output cell coupled to receive the p-bias voltage and the n-bias voltage, the first reference input/output cell configured to provide a first internal control voltage responsive in part to the p-bias voltage and the n-bias voltage; a second reference input/output cell coupled to receive the p-bias voltage and the n-bias voltage, the second reference input/output cell configured to provide a second internal control voltage responsive in part to the p-bias voltage and the n-bias voltage; the first reference input/output cell coupled to receive the second internal control voltage and configured to provide the first internal control voltage responsive in part to the second internal output voltage; the second reference input/output cell coupled to receive the first internal control voltage and configured to provide the second internal control voltage responsive in part to the first internal control voltage; an internal resistance configured to approximate transmission resistance, the internal resistance coupled to receive the first internal control voltage at one end and to receive the second internal control voltage at another end; the first reference input/output cell and the second reference input/output cell coupled together at a first node for providing a pull-up side reference voltage; and the first reference input/output cell and the second reference input/output cell coupled together at a second node for providing a pull-down side reference voltage.