Patent ID: 8606991
Filing Date: 2013-12-10
Classification: G11C

Abstract:
1. A method for refreshing dynamic random access memory (DRAM) having a plurality of banks, each of the banks including a plurality of rows, comprising: dividing all banks in DRAM into a plurality of groups of banks, each of the groups having n banks, wherein n is an integer greater than or equal to 1; determining a threshold of available retention time for each group of banks; and refreshing each row of banks in each group of banks, wherein performing a refresh for one row of a bank in one group of banks includes: determining whether a refresh operation for the row of the bank conflicts with an access operation for the bank where the row of the bank is located, wherein if there is a conflict, then determining whether to perform the refresh operation or the access operation for the current row of the bank; and if it is determined to perform the access operation, continuing the access operation, wherein determining whether to perform the refresh operation or the access operation for the current row of the bank includes performing the refresh operation if a difference between, a difference between the threshold of available retention time for a bank group and a group refresh time, and all required refresh time for non-refreshed rows in the bank group is less than a set threshold, wherein the group refresh time is a time difference from a start of refresh until current refresh for the bank group.