Patent ID: 6636821
Filing Date: 2003-10-21
Classification: H03K

Abstract:
An output driver impedance calibration circuit comprising:an output driver circuit having an output stage with a base transistor device; a plurality of calibration transistor devices in the output stage of the output driver circuit; means for activating in a time ordered sequence the base transistor device and then one at a time in the time ordered sequence each of the plurality of calibration transistor devices; means for providing a target reference voltage; a voltage comparator circuit for comparing the value of an output voltage of the output stage of the output driver circuit with the target reference voltage; means for storing the states of the plurality of calibration transistor devices when the output voltage attains the target reference voltage, to preserve the states of the plurality of calibration transistor devices and to calibrate the output impedance of the output driver circuit to a target output impedance.