Dynamic random access memory device with refreshing system powered with external power source in trimming stage instead of built-in step-down circuit

摘要

A dynamic random access memory device periodically refreshes data bits stored in the memory cells, and a refreshing system is incorporated in the dynamic random access memory device for incrementing a refresh address, wherein the refreshing system comprises an oscillator powered with a step-down voltage in the refreshment and with an external power voltage through a testing operation in a diagnostic mode, a clock generating unit for producing a clock signal defining an interval of each refreshing sequence, and a refresh address counter for producing an internal address signal indicative of the refresh address so that the frequency of a pulse signal produced by the oscillator is regulable without any influence of non-regulated step-down voltage.