Semiconductor devices having ZQ calibration circuits and calibration methods thereof
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United States of America Patent
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Jun 28, 2011
Grant Date -
Feb 3, 2011
app pub date -
Feb 4, 2010
filing date -
Aug 3, 2009
priority date (Note) -
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Abstract
Provided is a semiconductor device for performing a calibration operation without an external ZQ calibration command and a calibration method thereof. The semiconductor device includes a calibration circuit for performing a pull-down calibration operation in response to a pull-down calibration enable signal and a command control unit for generating the pull-down calibration enable signal in response to a DLL reset signal. The calibration method includes adjusting an impedance of a first pull-up resistance structure in response to pull-up calibration codes having a default value. A pull-down calibration enable signal may be generated in response to a DLL reset signal. A voltage of the first node and a reference voltage are compared by a comparator. The comparator outputs pull-down calibration codes based on the comparison. An impedance of a pull-down resistance structure is adjusted, so a resistance of the pull-down resistance structure is equal to a resistance of the first pull-up resistance structure.
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