US Patent 11527287 Drift aware read operations

Systems, methods and apparatus to read target memory cells having an associated reference memory cell configured to be representative of drift or changes in the threshold voltages of the target memory cells. The reference cell is programmed to a predetermined threshold level when the target cells are programmed to store data. In response to a command to read the target memory cells, estimation of a drift of the threshold voltage of the reference is performed in parallel with applying an initial voltage pulse to read the target cells. Based on a result of the drift estimation, voltage pulses used to read the target cells can be modified and/or added to account for the drift estimated using the reference cell.