Methods and systems for memory devices
AssigneesSpansion LLC, Advanced Micro Devices, Inc.
InventorsBryan William Hancock, Nicholas H. Tripsas, Richard C. Blish
Life of this patent
Estimating the term…
Abstract
One embodiment of the invention relates to a method for refreshing a nonvolatile memory array. In the method, a threshold voltage of a multi-bit memory cell is analyzed to determine if it has drifted outside of a number of allowable voltage windows, wherein each allowable voltage windows corresponds to a different multi-bit value. If the threshold voltage of the cell has drifted outside of the number of allowable voltage states, then the cell is recovered by adjusting at least one voltage boundary of at least one of the number of allowable voltage states.
Claims20
A method for recovering a nonvolatile memory array, comprising:
- analyzing whether a threshold voltage of a multi-bit memory cell has drifted outside of a number of allowable voltage windows, wherein each allowable voltage window corresponds to a different multi-bit value;
- and
- if the threshold voltage of the cell has drifted outside of the number of allowable voltage windows, then refreshing the cell by adjusting at least one voltage boundary of at least one of the number of allowable voltage windows.
A method for refreshing a nonvolatile memory array, comprising:
- analyzing a group of at least one memory cell to determine if a threshold voltage of one cell within the group has drifted outside of at least one allowable voltage window associated with the group;
- and
- if the threshold voltage of the one cell has drifted outside of the at least one voltage distribution window, refreshing the one cell by adjusting at least one voltage boundary of the at least one allowable voltage window.
A method for accessing a memory array, comprising:
- analyzing a group of at least one nonvolatile memory cell of the memory array to determine if a threshold voltage of one cell within the group has drifted outside of at least one allowable voltage window;
- recovering the one cell according to a first procedure if the drift occurred due to charge loss and according to a second procedure if the drift occurred due to charge gain.
A nonvolatile memory device comprising:
- an array of a multi-bit memory cells that are associated with number of allowable voltage windows, wherein each allowable voltage window corresponds to a different multi-bit value;
- a reference generator configured to provide an adjustable reference voltage;
- a sense amp associated with the multi-bit memory cells and configured to provide read data by comparing data stored within the cells to the adjustable reference voltage;
- and
- a controller configured to determine if the read data deviates from expected data, and refresh the array if there is such deviation.
Dependencies are inferred from the claim text.