Patent ID: 6944071

Claim:
An active termination circuit for setting the input impedance of a plurality of terminals to a predetermined value, the active termination circuit comprising: a respective first controllable impedance device coupled between a first supply voltage and each of the terminals, the impedance of the first controllable impedance device being controlled by an impedance control signal; a control circuit coupled to provide the impedance control signal to all of the first controllable impedance devices, the first control circuit comprising: a second controllable impedance device coupled between a second supply voltage and feedback node, the second controllable impedance device being a different controllable impedance device from the first controllable impedance devices, and the feedback node being different from one of the terminals, the impedance of the second controllable impedance device being controlled by the impedance control signal; a predetermined resistance coupled between the feedback node and a third supply voltage, the second controllable impedance device and the predetermined resistance forming a voltage divider between the second and third supply voltages to produce a feedback voltage at the feedback node; and a circuit generating the impedance control signal as a function of the feedback voltage so that magnitude of the feedback voltage is substantially constant.