Drift compensation in a flash memory
First Claim
1. A method of managing a plurality of memory cells, comprising the steps of:
- (a) obtaining a respective value of at least one environmental parameter of the plurality of memory cells; and
(b) adjusting a respective value of at least one reference voltage of the plurality of memory cells in accordance with said at least one obtained value.
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Accused Products
Abstract
A plurality of memory cells are managed by obtaining values of one or more environmental parameters of the cells and adjusting values of one or more reference voltages of the cells accordingly. Alternatively, a statistic of at least some of the cells, relative to a single reference parameter that corresponds to a control parameter of the cells, is measured, and the value of the reference voltage is adjusted accordingly. Examples of environmental parameters include program-erase cycle count, data retention time and temperature. Examples of reference voltages include read reference voltages and program verify reference voltages. Examples of statistics include the fraction of cells whose threshold voltages exceed initial lower bounds or initial medians.
190 Citations
21 Claims
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1. A method of managing a plurality of memory cells, comprising the steps of:
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(a) obtaining a respective value of at least one environmental parameter of the plurality of memory cells; and
(b) adjusting a respective value of at least one reference voltage of the plurality of memory cells in accordance with said at least one obtained value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A memory device, comprising:
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(a) a plurality of memory cells; and
(b) a controller operative to manage said plurality of memory cells by;
(i) obtaining a respective value of at least one environmental parameter of said plurality of memory cells, and (ii) adjusting a respective value of at least one reference voltage of said plurality of memory cells in accordance with said at least one obtained value.
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10. A method of managing a plurality of memory cells, comprising the steps of:
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(a) measuring a statistic of at least some of the memory cells relative to a single respective reference parameter of a reference voltage of the plurality of memory cells; and
(b) adjusting a respective value of said reference voltage in accordance with said measured statistic. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A memory device, comprising:
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(a) a plurality of memory cells; and
(b) a controller operative to manage said plurality of memory cells by;
(i) measuring a statistic of at least some of said memory cells relative to a single respective reference parameter of a reference voltage of said plurality of memory cells, and (ii) adjusting a respective value of said reference voltage in accordance with said measured statistic.
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Specification