Memory system and semiconductor memory device for enhancing bus efficiency and refresh method of the semiconductor memory device

Abstract

A memory system and a semiconductor memory device, which are capable of increasing memory bus efficiency and a refresh method of the semiconductor memory device are provided. A method for refreshing an open bank of a semiconductor memory device with a memory controller in a memory system including a plurality of semiconductor memory devices and the memory controller for controlling the plurality of semiconductor memory devices includes (a) applying a refresh command to each of the plurality of semiconductor memory device in order to the open bank; (b) precharging the open bank with each of the plurality of semiconductor memory devices if the refresh command is applied to the each of the plurality of semiconductor memory devices; and (c) refreshing the precharged bank with each of the plurality of semiconductor memory devices. The memory controller does not need to apply a precharge command to the semiconductor memory device before applying a refresh command to the semiconductor memory device but applies only the refresh command to the semiconductor memory device in order to perform a refresh operation on an open bank of the semiconductor memory device. In addition, the semiconductor memory device automatically performs an activation operation on the completely refreshed bank after refreshing the open bank, thereby considerably increasing the efficiency of the memory bus.