Methods of Cell Population Distribution Assisted Read Margining
First Claim
1. In a memory device having a plurality of memory cells each storing one of at least two data states, a method of reading the memory cells to determine which of the memory cells contain data corresponding to a selected one of the data states, the method comprising:
- evaluating the memory cells at a first reference condition;
evaluating the memory cells at a plurality of secondary reference conditions; and
determining a read condition at which to determine the memory cells that contain data corresponding to said selected one of the data states based on comparing the number of memory cells evaluated at the first reference condition and the second reference conditions, wherein the read condition is determined based on the rate of change of number of memory cells evaluated at the plurality of reference conditions.
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Accused Products
Abstract
A memory using techniques to extract the data content of its storage elements, when the distribution of stored states is degraded, is presented. If the distribution of stored states has degraded, secondary evaluations of the memory cells are performed using modified read conditions. Based upon the results of these supplemental evaluations, the memory device determines the read conditions at which to best decide the data stored.
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Citations
34 Claims
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1. In a memory device having a plurality of memory cells each storing one of at least two data states, a method of reading the memory cells to determine which of the memory cells contain data corresponding to a selected one of the data states, the method comprising:
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evaluating the memory cells at a first reference condition; evaluating the memory cells at a plurality of secondary reference conditions; and determining a read condition at which to determine the memory cells that contain data corresponding to said selected one of the data states based on comparing the number of memory cells evaluated at the first reference condition and the second reference conditions, wherein the read condition is determined based on the rate of change of number of memory cells evaluated at the plurality of reference conditions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A of method determining the data content of a memory device having a plurality of memory cells each storing one of at least two data states, comprising:
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evaluating the memory cells using standard read conditions; determining whether the evaluation using standard read conditions has an unacceptable level of error; in response to the evaluation using standard read conditions having an unacceptable level of error, performing evaluations of the memory cells using a plurality of secondary read conditions; extracting information on the distribution of programmed state populations of the memory cells based on the results of the evaluations using the standard read conditions and the plurality of secondary read conditions; and determining modified read conditions differing from the standard read conditions at which to evaluate the memory cells to determine their data content based on said information on the distribution of programmed state populations. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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Specification