Patent attributes
The present invention relates to a semiconductor memory device to execute a refresh operation in such a manner that an entry and an exit of a self refresh mode is carried out. The present invention uses only external clock signals without a clock enable signal or an auto refresh command and therefore it is possible to implement a simple circuit for the self refresh. A semiconductor memory device includes a self refresh enable signal generator for outputting an activated self refresh enable signal when positive and negative external clock signals are in phase and a de-activated self refresh enable signal when the positive and negative external clock signals are out of phase and a self refresh block for performing a self refresh operation in response to the activated self refresh enable signal.
