| 摘要 |
A synchronous memory device having an output driver control device is provided to perform stable operation of an output driver, by making the output driver to be enabled after an internal clock outputted from a DLL circuit becomes stable. In a synchronous memory device having an output driver control device(220), a DLL circuit(200) receives an external clock and outputs an internal clock. An output driver(210) outputs data in synchronization with the internal clock. The output driver control device controls the operation of the output driver. The output driver control device activates the output driver, after receiving a control signal indicating that the internal clock is in a stable state by locking, from the DLL circuit. The DLL circuit comprises a counter(23) counting the number of toggling of the external clock, and outputs an enable signal enabling the output driver control device if the number of toggling of the external clock exceeds a predetermined number.
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