SENSING SCHEMES FOR FLASH MEMORY WITH MULTILEVEL CELLS

摘要

Methods and apparatus for determining the state of a memory cell having more than two possible states are disclosed. For a first embodiment, the state of a flash cell (401) having n states, where n is a power of two, is determined by selectively comparing the threshold voltage Vt of a selected memory cell to (n-1) reference voltages. For every two states, a single comparator (460 and 470) is provided such that the total number of comparators is equal to the number of bits stored in the memory cell.