US Patent 7215588 Apparatus for controlling self-refresh period in memory device

Disclosed is an apparatus for controlling a self-refresh period in a memory device capable of normally performing a self-refresh operation that is indispensable to the operation of a volatile memory device using a refresh period control even if the inner temperature of the memory device is changed. The apparatus determines different bank refresh periods according to the self-refresh entering time in a self-refresh mode, and thus the refresh operation can properly be performed to cope with the change of inner temperature of the memory device.