Memory cell shift estimation method and apparatus
AssigneeMicron Technology, Inc.
InventorVishal Sarin
Life of this patent
Estimating the term…
Abstract
Memory devices and methods are disclosed, such as those facilitating interpolation methods for reference memory cells based on their reference state and/or location in an array of memory cells. For example, a group of reference cells programmed to a subset of possible data states are utilized to interpolate for data states other than those in the subset. Such embodiments might be used to reduce the quantity of reference cells required.
Claims43
A method for estimating a memory cell threshold voltage shift utilizing two or more memory cells programmed to two or more initial threshold voltages, comprising:
- determining a threshold voltage drift of a first memory cell;
- determining a threshold voltage drift of a second memory cell;
- and
- generating the estimated threshold voltage shift of a third memory cell at least partially in response to the determined threshold voltage drifts of the first and the second memory cells.
A method for estimating a memory cell reference threshold voltage from two or more threshold voltages initially programmed into two or more reference cells of an array of memory cells, comprising:
- determining a threshold voltage of a first reference cell;
- determining a threshold voltage of a second reference cell;
- and
- estimating the reference threshold voltage wherein the estimated reference threshold voltage is at least in part a function of the measured threshold voltages of the first and the second reference cells.
A method for estimating a change in threshold voltage of a user data memory cell from two or more reference threshold voltages initially programmed into two or more reference memory cells, comprising:
- determining a change in a threshold voltage of a first reference cell;
- determining a change in a threshold voltage of a second reference cell;
- and
- estimating a change in a threshold voltage of the user data memory cell at least partially based on the changes in the threshold voltage of the first and the second reference cells.
A method for estimating a change in a threshold voltage of a memory cell, comprising:
- determining a threshold voltage of a first reference memory cell initially programmed to a first initial threshold voltage wherein a first change value comprises a difference between the first initial threshold voltage and the determined threshold voltage of the first reference cell;
- determining a threshold voltage of a second reference memory cell initially programmed to a second initial threshold voltage wherein a second change value comprises a difference between the second initial threshold voltage and the determined threshold voltage of the second reference cell;
- and
- estimating the change in the threshold voltage of the memory cell at least partially based on the first change value and the second change value;
- and
- wherein the first initial threshold voltage and the second initial threshold voltage are different.
A memory device, comprising:
- an array of memory cells;
- and
- control circuitry, wherein the control circuitry is configured to program a first reference memory cell of the array of memory cells to a first initial threshold voltage, program a second reference memory cell of the array of memory cells to a second initial threshold voltage, measure a threshold voltage of the first reference memory cell subsequent to programming the first reference memory cell, measure a threshold voltage of the second reference memory cell subsequent to programming the second reference memory cell, and generate an estimated change in a memory cell that was not initially programmed to either the first or the second initial threshold voltages at least partially in response to the measured threshold voltage of the first reference memory cell and the measured threshold voltage of the second reference memory cell.
An electronic system, comprising:
- a host configured to generate memory control signals;
- and
- a memory device coupled to the host and configured to operate in response to the memory control signals, the memory device comprising:
- an array of memory cells comprising a plurality of reference memory cells and a plurality of user data memory cells;
- and
- control circuitry, wherein the control circuitry is configured to program two or more reference memory cells to two or more reference threshold voltages, measure a threshold level of two or more reference memory cells, and generate an estimated reference threshold voltage in response to the measured threshold levels of two or more reference memory cells programmed to two or more reference levels.
Dependencies are inferred from the claim text.