Refreshing data stored in a flash memory

• US 20050243626A1
• Filed: 10/27/2004
• Published: 11/03/2005
• Est. Priority Date: 04/29/2004
• Status: Active Grant

• Current Assignee: Western Digital Israel Limited (Western Digital Corporation)
• Original Assignee: M-Systems Flash Disk Pioneers Ltd. (Western Digital Corporation)
• Inventors: Ronen, Amir
• Granted Patent: US 7,325,090 B2
• Time in Patent Office: Days
• US Class Current: 365/222
• CPC Class Codes: G11C 11/406 Management or control of the refreshing or charge-regeneration cycles
• CPC Class Codes: G11C 11/40622 Partial refresh of memory arrays
• CPC Class Codes: G11C 16/3418 Disturbance prevention or evaluation; Refreshing of disturbed memory data
• CPC Class Codes: G11C 16/3431 Circuits or methods to detect disturbed nonvolatile memory cells, e.g. which still read as programmed but with threshold less than the program verify threshold or read as erased but with threshold greater than the erase verify threshold, and to reverse the disturbance via a refreshing programming or erasing step

Abstract

Data are stored in one or more cells of a non-volatile memory, and are refreshed according to a predetermined condition. The data are refreshed either in-place or out-of-place. The condition may be related to the age of the data. Alternatively, the data are refreshed periodically, or when the system that includes the memory boots or dismounts, or according to the type of the data.

Claims

1. A method of managing a memory, comprising the steps of:

(a) storing data in at least one cell of the memory; and

(b) refreshing said data that are stored in said at least one cell, according to a predetermined condition.

2. The method of claim 1, wherein said storing is effected at a storage date, and wherein said condition includes said storage date.

3. The method of claim 2, wherein said condition is that a predetermined time interval has elapsed since said storage date.

4. The method of claim 3, further comprising the steps of:

(c) recording a timestamp indicative of said storage date; and

(d) testing said condition by comparing said timestamp to a clock of a system that includes the memory.

5. The method of claim 1, wherein said condition is an occurrence of one of a plurality of predetermined refresh dates.

6. The method of claim 5, wherein said plurality of refresh dates includes at least three uniformly spaced dates.

7. The method of claim 5, wherein said plurality of refresh dates includes at least three dates having a monotonically decreasing spacing.

8. The method of claim 1, wherein said condition is that a system that includes the memory boots.

9. The method of claim 1, wherein said condition is that a system that includes the memory dismounts.

10. The method of claim 1, wherein said condition is related to a type of said data.

11. The method of claim 1, wherein data stored in different partitions of the memory have different respective said conditions.

12. The method of claim 1, wherein said refreshing is effected in-place.

13. The method of claim 1, wherein said refreshing is effected out-of-place.

14. A memory device comprising:

(a) at least one cell; and

(b) a controller operative;

(i) to store data in said at least one cell, and

(ii) to refresh said data according to a predetermined condition.

15. A system for storing data, comprising:

(a) a memory device that includes at least one cell; and

(b) a processor operative;

(i) to store the data in said at least one cell, and

(ii) to refresh the data according to a predetermined condition.