Device and method for managing power of dram by selfrefresh

PURPOSE: To provide a DRAM system in which power consumption is reduced up to a maximum. CONSTITUTION: A DRAM 30 is provided with a power managing circuit 56 for removing power from a circuit group 134 on the DRAM, which is not required for self-refresh, and timewisely relatively turning off another circuit group 120 required for self-refresh in a refresh cycle. This power managing circuit 56 is provided with a counter 108 and simple decoder circuits 112 and 114 for decoding the binary output of this counter. COPYRIGHT: (C)1994,JPO