Threshold estimation in NAND flash devices
AssigneeSamsung Electronics Co., Ltd.
InventorsElisha Halperin, Evgeny Blaichman, Amit Berman
Life of this patent
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Abstract
A method for determining an optimal threshold of a nonvolatile memory device, the method including: reading a page from a nonvolatile memory device with a default threshold and attempting to hard decode the page using the default threshold; reading the page two more times with a predetermined offset voltage when the hard decoding fails and attempting to soft decode the page using the default threshold; approximating an empirical distribution of successfully decoded bits with a Gaussian distribution for each level; finding an intersection of the Gaussian distributions; and setting the intersection as a new reading threshold and reading the page again with the new reading threshold.
Claims8
A method for determining an optimal threshold of a nonvolatile memory device, the method comprising:
- partially decoding a page from a nonvolatile memory device;
- approximating an empirical distribution of successfully decoded bits with a Gaussian distribution for each high and low level, wherein the successful decoded bits are obtained from some but not all frames of the page;
- finding an intersection of the Gaussian distributions;
- and
- setting the intersection as a new reading threshold and reading the page again with the new reading threshold.
A method for determining optimal threshold of a nonvolatile memory device, the method comprising:
- partially decoding a page from a nonvolatile memory device;
- approximating an empirical distribution of successfully decoded bits with a Gaussian distribution for each high and low level;
- finding an intersection of the Gaussian distributions;
- and
- setting the intersection as a new reading threshold and reading the page again with the new reading threshold,
- wherein if reading the page again with the new reading threshold fails, a less read estimation (LRE) is performed.
Dependencies are inferred from the claim text.