Method and apparatus for read measurement of a plurality of resistive memory cells

摘要

A method and apparatus for read measurement or data sensing a plurality N of resistive memory cells, having a plurality K of programmable levels (figures 2-4), including applying a first read voltage to each of the N memory cells and measuring a first read current, (101 figure 1). A further step (102 figure 1) is executed to determine a respective second read voltage based on the first read current measured at the memory cell and a target read current determined for the memory cell for each of the N memory cells. A subsequent step (103 figure 1) involves applying the respective determined second read voltage to the memory cell for obtaining a second read current for each of the N memory cells. The second read voltage may be determined such that the second read current is constant for all memory cells programmed with the same level or may have one respective target current for each of the K programmed levels. The target currents may be determined as the level means of the first read currents, as blind estimations or may involve the use of a number of identical reference cells. The method may also include data mapping of read currents to the respective cells. The apparatus for measurement includes a voltage generator 13 for applying a bias to the bit line connected to the resistive memory, a current detector 14 for measuring the current through the resistive memory device 11 and a measurement controller 15 all of which may be computerised.