Low voltage differential receiver/transmitter and calibration method thereof

Abstract

A low-voltage transmitter and receiver adapted for differential signaling via transmission lines between integrated circuits enables operation at very-high data exchange rates. Such data transmission is achieved in a manner that minimizes reflected energy and minimizes crosstalk between signals propagating over neighboring transmission lines. In achieving optimal transmission characteristics, a bridge circuit is employed to drive the signal. The bridge circuit is connected in series between a pull-up and pull-down resistance, their respective resistance values being programmable to maintain optimal communication rates and quality. The pull-up and pull-down resistors preferably comprise a bank of transistors having source-to-drain resistance values that are binary multiples of each other. The transistors are preferably coupled in parallel with each other and in parallel with a resistor, such that the transistors can be selectively activated by a binary voltage control data word. By activating different transistors in the network, different overall resistance values can be achieved. A calibration circuit is provided for periodic calibration of the resistance values to maintain optimal operation with varying system supply voltage and temperature.