Block read count voltage adjustment
First Claim
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1. A NAND memory device comprising:
- a NAND memory array including a first pool of memory;
a controller executing instructions and performing operations comprising;
receiving a command from a host to read a value of at least one cell from the first pool of memory;
determining a read voltage to apply to the at least one cell by adding a first offset value to a base read voltage, the first offset value calculated as a stepwise function of a count of a number of previous reads during a period of time to a group of cells, the group of cells including the at least one cell; and
applying the read voltage to the at least one cell.
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Abstract
Disclosed in some examples, are methods, systems, and machine readable mediums which compensate for read-disturb effects by shifting the read voltages used to read the value in a NAND cell based upon a read counter. For example, the NAND memory device may have a read counter that corresponds to a group of NAND cells (e.g., a page, a block, a superblock). Anytime a NAND cell in the group is read, the read counter may be incremented. The read voltage, Vread, may be adjusted based on the read counter to account for the read disturb voltage.
41 Citations
17 Claims
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1. A NAND memory device comprising:
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a NAND memory array including a first pool of memory; a controller executing instructions and performing operations comprising; receiving a command from a host to read a value of at least one cell from the first pool of memory; determining a read voltage to apply to the at least one cell by adding a first offset value to a base read voltage, the first offset value calculated as a stepwise function of a count of a number of previous reads during a period of time to a group of cells, the group of cells including the at least one cell; and applying the read voltage to the at least one cell. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method performed by a NAND memory device, the method comprising:
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receiving a command from a host to read a value of at least one cell from a first pool of memory of the NAND memory device; determining a read voltage to apply to the at least one cell by adding a first offset value to a base read voltage, the first offset value calculated as a stepwise function of a count of a number of previous reads during a period of time to a group of cells, the group of cells including the at least one cell; and applying the read voltage to the at least one cell. - View Dependent Claims (9, 10, 11)
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12. A machine-readable medium comprising instructions, which performed by a machine, causes the machine to perform operations comprising:
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receiving a command from a host to read a value of at least one cell from a first pool of memory cells in a NAND memory device; determining a read voltage to apply to the at least one cell by adding a first offset value to a base read voltage, the first offset value calculated as a stepwise function of a count of a number of previous reads during a period of time to a group of cells, the group of cells including the at least one cell; and applying the read voltage to the at least one cell. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification