A dynamic reference scheme for nonvolatile ferroelectric RAM

We report on a novel reference voltage scheme for FRAMs which solves most problems like fatigue, temperature dependency, voltage drop, etc still present in other reference schemes: dynamic reference scheme. It tracks the variations of the ferroelectric capacitors in the memory and provides a common reference voltage line for all sense amplifiers on chip or different reference voltages for different memory banks. No dedicated reference cells are required, instead the memory cells themselves are utilized to generate the reference voltage by periodical test of their voltage levels or by setting a signal that starts the test. This scheme extends life-time and reliability of the memory and enables a self test and repair capability