Data storage device and operating method thereof

Patent metadata

Field	Value
Publication number	US-9741402-B2
Application number	US-201615060724-A
Country	US
Kind code	B2
Filing date	Mar 4, 2016
Priority date	Nov 18, 2015
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

A data storage device includes a memory device including a plurality of memory cells; and a controller suitable for determining, based on data read from the plurality of memory cells, section cell numbers corresponding to threshold voltage sections, and for determining an average threshold voltage of a threshold voltage distribution selected among a plurality of threshold voltage distributions of the memory cells which are estimated based on the section cell numbers, based on a Gaussian distribution function.

First claim

What is claimed is:

1. A data storage device comprising:
a memory device including a plurality of memory cells; and
a controller suitable for determining, based on data read from the plurality of memory cells, section cell numbers corresponding to threshold voltage sections, and for determining an average threshold voltage of a threshold voltage distribution selected among a plurality of threshold voltage distributions of the memory cells which are estimated based on the section cell numbers, based on a Gaussian distribution function.

2. The data storage device according to claim 1 , wherein the controller is suitable for determining the section cell numbers corresponding to the threshold voltage sections based on the data read from the plurality of memory cells by applying at least one reference voltage to the memory cells,
wherein the threshold voltage sections are divided by the reference voltage.

3. The data storage device according to claim 2 ,
wherein the controller counts the number of memory cells corresponding to respective patterns of the data, as the section cell numbers, and
wherein the patterns correspond to the threshold voltage sections.

4. The data storage device according to claim 2 , wherein the controller determines an area ratio of a partial distribution which is formed as the selected threshold voltage distribution is divided by the reference voltage, based on the section cell numbers, and determines the average threshold voltage, based on the area ratio and a predetermined variance value corresponding to the selected threshold voltage distribution.

5. The data storage device according to claim 4 , wherein the controller determines a partial cell number corresponding to the partial distribution, based on the section cell numbers and distribution cell numbers corresponding to the threshold voltage distributions, and determines the area ratio, based on a ratio of the partial cell number with respect to a distribution cell number corresponding to the selected threshold voltage distribution.

6. The data storage device according to claim 4 , wherein the controller determines the average threshold voltage by applying the area ratio to an integral equation for the Gaussian distribution function.

7. The data storage device according to claim 4 , wherein the controller determines the average threshold voltage by referring to a table which includes values of a reverse function of a Q function, the values including a value corresponding to the area ratio.

8. The data storage device according to claim 2 , wherein the controller determines whether to adjust the reference voltage, based on the section cell numbers, set a new reference voltage by adjusting the reference voltage according to a determination result, and iterates determining of section cell numbers based on the new reference voltage.

9. The data storage device according to claim 8 , wherein the controller determines whether the reference voltage is positioned in a reliable section excluding a lower unreliable section and an upper unreliable section in the selected threshold voltage distribution, based on the section cell numbers, and determines to adjust the reference voltage, in the case where the reference voltage is not positioned in the reliable section.

10. The data storage device according to claim 9 , wherein the controller determines a cumulative cell number which is the number of memory cells having threshold voltages smaller than the reference voltage, based on the section cell numbers, and determines whether the reference voltage is positioned in the reliable section, by determining whether the cumulative cell number is included in a predetermined range with respect to a predetermined reference cell number.

11. The data storage device according to claim 9 , wherein the controller determines an area ratio of a partial distribution which is formed as the selected threshold voltage distribution is divided by the reference voltage, based on the section cell numbers, and determines whether the reference voltage is positioned in the reliable section, by comparing the area ratio and area ratios of the lower unreliable section and the upper unreliable section.

12. The data storage device according to claim 9 , wherein each of the lower unreliable section and the upper unreliable section has an area ratio larger than a cumulative error rate corresponding to the selected threshold voltage distribution.

13. The data storage device according to claim 8 , wherein the controller sets an average threshold voltage of a selected threshold voltage distribution corresponding to the reference voltage, as the new reference voltage.

14. The data storage device according to claim 8 , wherein, when the reference voltage is positioned in any one of a lower unreliable section and an upper unreliable section of a corresponding selected threshold voltage distribution, the controller acquires another reference voltage which is positioned in the other of the lower unreliable section and the upper unreliable section, and sets a middle value of the reference voltage and the another reference voltage, as the new reference voltage.

15. The data storage device according to claim 8 , wherein, when another reference voltage adjacent to the reference voltage is positioned in a reliable section of another threshold voltage distribution adjacent to the selected threshold voltage distribution corresponding to the reference voltage, the controller sets the new reference voltage by adjusting, using a predetermined offset value, the another reference voltage.

16. The data storage device according to claim 1 , wherein the controller is further suitable for estimating one or more optimal read voltages for reading data stored in the memory cells, based on the average threshold voltages.

17. The data storage device according to claim 16 , wherein the optimal read voltages include a middle value of adjacent average threshold voltages among the average threshold voltages.

18. The data storage device according to claim 16 , wherein the optimal read voltages include a value obtained by adding or subtracting a predetermined offset value to or from at least one among the average threshold voltages.

19. A method for operating a data storage device, comprising:
determining, based on data read from a plurality of memory cells, section cell numbers corresponding to threshold voltage sections which are divided by at least one reference voltage; and
determining an average threshold voltage of a threshold voltage distribution selected among a plurality of threshold voltage distributions of the memory cells which are estimated based on the section cell numbers, based on a Gaussian distribution function.

20. A data storage device comprising:
a memory device including a plurality of memory cells; and
a controller suitable for determining average threshold voltages of threshold voltage distributions selected among a plurality of threshold voltage distributions of the memory cells, by applying area ratios of partial distributions of the selected threshold voltage distributions to Gaussian modeling, and estimating one or more optimal read voltages for reading data stored in the memory cells, based on the average threshold voltages.

Assignees

• Sk Hynix Inc

Inventors

• Jeon Myeong Woon

Classifications

• G11C7/14 Primary

  Dummy cell management; Sense reference voltage generators · CPC title

• G11C7/12 Primary

  Bit line control circuits, e.g. drivers, boosters, pull-up circuits, pull-down circuits, precharging circuits, equalising circuits, for bit lines · CPC title

• G11C16/28

  using differential sensing or reference cells, e.g. dummy cells · CPC title

• G11C11/5642

  Sensing or reading circuits; Data output circuits · CPC title

• G11C16/3404 Primary

  Convergence or correction of memory cell threshold voltages; Repair or recovery of overerased or overprogrammed cells · CPC title