Apparatus and method for refreshing memory

Abstract

Apparatuses for executing row hammer refresh are described. An example apparatus includes: memory banks, each memory bank of the memory banks includes a latch that stores a row address; and a time based sampling circuit. The time based sampling circuit includes: a sampling timing generator that provides a timing signal of sampling a row address; and bank sampling circuits, wherein each bank sampling circuit of the bank sampling circuits is included in a corresponding memory bank of the memory banks and provides a sampling signal to the latch in the corresponding memory bank responsive to the timing signal of sampling the row address; and an interval measurement circuit that receives an oscillation signal, measures an interval of a row hammer refresh execution based on a cycle of the oscillation signal, and further provides a steal rate timing signal for adjusting a steal rate to the sampling timing generator.

Description

Background technique [0001] High data reliability, high memory access speed, and reduced chip size are required features of semiconductor memories. [0002] A dynamic random access memory (DRAM), which is a typical semiconductor memory device, stores information by electric charges accumulated in cell capacitors, and thus information is lost unless a refresh operation is performed periodically. Therefore, a refresh command instructing a refresh operation is periodically issued from the control means, which controls the DRAM. A refresh command is issued from the control device at a frequency that all word lines must be refreshed once within one refresh cycle period (for example, 64 milliseconds). In addition, the refresh command is periodically invoked as row hammer refresh (Rhr), which maintains data retention of the victim's row address caused by the row hammer attack. [0003] However, conventional static row hammer refresh rate control cannot prevent bit errors due to row...

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Problems solved by technology

[0003] However, conventional static row hammer refresh rate control cannot prevent bit errors due to row hammer effects that may occur at various timings for various reasons and dynamic row hammer refresh rate control may be desired

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