Abstract: A pull-up circuit has substantially linear current-voltage (I-V) characteristics for use in a bus system, such as in an open drain bus architecture type system. Operation in the linear region of the I-V characteristics is useful in high frequency input/output circuits. The pull-up circuit includes a transistor and a single termination resistor coupled to the transistor, and is simpler than other types of pull-up circuits. This simplicity in design saves area on a chip. The termination resistor in the pull-up circuit can be an n-well resistor formed on the same chip as the transistor, thereby further contributing to the savings in chip area.

Abstract: In a system, such as an open-drain bus architecture system, a termination impedance can be dynamically coupled or de-coupled from a bus. The termination impedance is coupled to the bus by a dynamic control circuit if a signal is being received from the bus or if a binary 1 is driven on the bus. The termination impedance is de-coupled from the bus by the dynamic control circuit if a binary 0 is driven on the bus. Coupling the termination impedance to the bus improves signal quality by providing a matching impedance. De-coupling the termination impedance reduces power dissipation and improves receiver noise margin.