Nonvolatile memory system and data recovery method thereof

Patent metadata

Field	Value
Publication number	US-2016124805-A1
Application number	US-201514676341-A
Country	US
Kind code	A1
Filing date	Apr 1, 2015
Priority date	Nov 3, 2014
Publication date	May 5, 2016
Grant date	—

Abstract

A nonvolatile memory system includes a nonvolatile memory device including a plurality of memory cells; and a memory controller suitable for recovering normal data based on a recovery read level interval when an error occurs in the normal data read from the memory cells by using a reference read level, wherein the memory controller generates N distribution measurement values by measuring distribution values of threshold voltage levels of the memory cells at N respective distribution read levels, which have a preset read level interval with the reference read level serving as a center, and determines the recovery read level interval through calculating variations of the N distribution measurement values by using a linear equation, where ‘N’ is a natural number equal to or larger than 2.

First claim

What is claimed is:

1 . A nonvolatile memory system comprising:
a nonvolatile memory device including a plurality of memory cells; and a memory controller suitable for recovering normal data based on a recovery read level interval when an error occurs in the normal data read from the memory cells by using a reference read level, wherein the memory controller generates N distribution measurement values by measuring distribution values of threshold voltage levels of the memory cells at N distribution read levels, which have a preset read level interval with the reference read level serving as a center, and determines the recovery read level interval through calculating variations of the N distribution measurement values by using a linear equation, where ‘N’ is a natural number equal to or greater than 2.

2 . The nonvolatile memory system according to claim 1 , wherein the memory controller receives the recovery read level interval, as a read interval of a log likelihood ratio (LLR), and performs a low density parity check (LDPC) for the normal data to recover the normal data.

3 . The nonvolatile memory system according to claim 1 , wherein the preset read level interval corresponds to K times a minimum read level interval that is controllable to read data stored in the memory cells, where ‘K’ is a natural number equal to or greater than 2.

4 . The nonvolatile memory system according to claim 3 , wherein the memory controller, during an error correcting operation mode, alternately reads N distribution data and N measurement data from the memory cells by alternately using the N distribution read levels and N measurement read levels, which are respectively close to the N distribution read levels with the minimum read level interval, compares the N distribution data and the N measurement data to generate differences thereof as the N distribution measurement values.

5 . The nonvolatile memory system according to claim 4 , wherein the memory controller, during the error correcting operation mode, generates N distribution variation values by dividing the respective N distribution measurement values by the minimum read level interval of K times for comparting the preset read level interval, and determines an interval between read levels corresponding to level value intercepts in both directions from the reference read level serving as a center, as the recovery read level interval, by extending variations of the respective N distribution variation values by using a linear equation.

6 . The nonvolatile memory system according to claim 5 , further comprising:
a read operation unit suitable for generating the reference read level, the N distribution read levels or the N measurement read levels based on a level control signal, and reading the data of the memory cells by using the read levels as a reference.

7 . The nonvolatile memory system according to claim 6 , wherein the memory controller includes:
a signal generation unit suitable for generating the level control signal with a value for controlling the normal data read from the read operation unit, outside the error correcting operation mode, and generating the level control signal with a value for controlling the N distribution data or the N measurement data read from the read operation unit, during the error correcting operation mode; a counting unit suitable for counting differences of the N distribution data and the N measurement data to generate the N distribution measurement values, during the error correcting operation mode; a storage unit suitable for storing the N distribution measurement values and the N distribution variation values; a first calculation unit suitable for reading the respective N distribution measurement values stored in the storage unit, performing calculations of dividing the respective N distribution measurement values by the minimum read level interval of K times for comparting the preset read level interval, and storing the N distribution variation values generated by the calculations, in the storage unit; a second calculation unit suitable for reading the respective N distribution variation values stored in the storage unit, generating the linear equation by calculating variations of the respective N distribution variation values, finding the read levels corresponding to the level value intercepts by using the linear equation, and determining the interval between the two found read levels, as the recovery read level interval; and an error correcting operation unit suitable for detecting, outside the error correcting operation mode, whether an error occurs in the normal data, and determining whether to enter the error correcting operation mode, and recovering, during the error correcting operation mode, the normal data based on the recovery read level interval.

8 . The nonvolatile memory system according to claim 7 , wherein the storage unit includes:
N first storages for storing the respective N distribution measurement values; and N second storages for storing the respective N distribution variation values.

9 . The nonvolatile memory system according to claim 7 , wherein the storage unit includes N storages suitable for storing the respective N distribution measurement values based on an operation result of the counting unit, and storing the respective N distribution variation values based on an operation result of the first calculation unit.

10 . A nonvolatile memory system comprising:
a nonvolatile memory device suitable for generating N distribution measurement values by measuring distribution values of threshold voltage levels of a plurality of memory cells, by respectively using N distribution read levels, which have a preset read level interval with a reference read level serving as a center, during an error correcting operation mode, where ‘N’ is a natural number equal to or greater than 2; and a memory controller suitable for determining to enter the error correcting operation mode when an error occurs in normal data read from the memory cells by using the reference read level, outside the error correcting operation mode, and recovering the normal data based on a recovery read level interval determined through calculating variations of the respective N distribution measurement values by using a linear equation, during the error correcting operation mode.

11 . The nonvolatile memory system according to claim 10 , wherein the memory controller receives the recovery read level interval, as a read interval of an LLR, and performs an LDPC for the normal data to recover the normal data.

12 . The nonvolatile memory system according to claim 10 , wherein the preset read level interval corresponds to K times a minimum read level interval that is controllable to read data stored in the memory cells, where ‘K’ is a natural number equal to or greater than 2.

13 . The nonvolatile memory system according to claim 12 , wherein the nonvolatile memory device, during the error correcting operation mode, alternately reads N distribution data and N measurement data from the memory cells by alternately using the N distribution read levels and N measurement read levels, which are respectively close to the N distribution read levels with the minimum read level interval, and compares the N distribution data and the N measurement data to generate differences thereof as the N distribution measurement values.

14 . The nonvolatile memory system according to claim 13 , wherein the memory controller, during the error correcting operation mode, generates N distribution variation values by dividing the respective N distribution measurement values by the mini

Assignees

• Sk Hynix Inc

Inventors

• Lee Hyung-Min

Classifications

• G11C29/52 Primary

  Protection of memory contents; Detection of errors in memory contents · CPC title

• G06F11/1068 Primary

  in sector programmable memories, e.g. flash disk (G06F11/1072 takes precedence) · CPC title

• G11C29/021

  in voltage or current generators · CPC title

• G06F11/1048

  using arrangements adapted for a specific error detection or correction feature · CPC title

• G11C16/3418

  Disturbance prevention or evaluation; Refreshing of disturbed memory data · CPC title