Importance

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Abstract

An on-chip resistor is calibrated with a sense circuit that compares a resistance associated with an off-chip resistor to the on-chip resistor via a current-mirror circuit and a comparator. A digital counter circuit evaluates the comparison and adjusts its count such that a variable digital control signal is provided to the on-chip resistor circuit. During the calibration of the on-chip resistor circuit, the resistance of the on-chip resistor can be matched to the resistance of the off-chip resistor according to a scaling factor (e.g., 1.times., 2.times., 2.5.times., 10.times., etc.) as may be desired. Once the resistance associated with the on-chip resistor circuit is sufficiently adjusted, another on-chip resistor (e.g., a terminating resistor of another circuit) can be adjusted from the counter value. Various other circuits can be disabled during the calibration of the on-chip resistor such that additional sources of error (e.g., supply variation, ground bounce, noise, etc.) are minimized.

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First Claim