| 摘要 |
A calibration circuit includes replica buffers that have a substantially same circuit configuration as at least a part of an output buffer, an oscillator circuit that generates an internal clock in response to issuance of a calibration command, and a control circuit that controls an impedance of the replica buffers in synchronization with the internal clock. According to the present invention, because a calibration operation that does not depend on an external clock is performed, even when a frequency of the external clock is changed according to an operation mode or the like, it is possible to maintain a constant period of time given to a single adjustment step or a constant time required for a series of calibration operations.
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