Integrated circuit with programmable-impedance output buffer and method therefor

摘要

An impedance matching between two integrated circuits is achieved using an impedance measuring circuit in the integrated circuit that contains an impedance-programmable output buffer (IPOB) that is to have its output impedance changed. The impedance measuring device is directly connected to the output of the IPOB so that it is detecting the same impedance that the IPOB will drive and thereby avoids the errors of measuring the resistance of a device that imperfectly models the actual impedance. The impedance measuring device is preferably an analog to digital (A/D) converter that provides a digital output relative to the voltage present on the same terminal as the output of the IPOB. By having the A/D converter on the same integrated circuit as the IPOB, communications difficulties between the A/D converter and the IPOB are minimal.