A circuit for refreshing data stored in an array of dynamic memory cells is provided. The circuit includes an integrated circuit chip. The chip has the array of memory cells formed thereon. The circuit also includes a refresh rate analysis circuit for determining data retention times in each one of the memory cells and from such determination refresh address modification signals. Also provided is a refresh address generator formed on the chip and fed by refresh command signals generated externally of the chip and by the address modification signals. The refresh address generator supplies an internal refresh commands along with refresh addresses to the array of memory cells. The cells have data stored therein refreshed in response to such internal refresh commands. The refresh rate analysis circuit determines cells in the array having data retention times less than a predetermined value.