Method and apparatus for selective use of wear-leveling to store data in a memory

• US 9,099,182 B1
• Filed: 05/15/2014
• Issued: 08/04/2015
• Est. Priority Date: 12/20/2006
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Montierth, Mark D., Briggs, Randall D., Keithley, Douglas G.
• Primary Examiner(s): Mai, Son
• Application Number:
  US14/278,932
• Time in Patent Office: 446 Days
• Field of Search: 365/185.09
• US Class Current: 1/1
• CPC Class Codes: G11C 16/06 Auxiliary circuits, e.g. for writing into memory
• CPC Class Codes: G11C 16/10 Programming or data input circuits
• 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
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles

Abstract

Semi-volatile NAND flash memory systems, apparatuses, and methods for use are described herein. According to various embodiments, a semi-volatile NAND flash memory may be partitioned into various retention regions. Other embodiments may be described and claimed.

Claims

1. A method comprising:

receiving data to be stored to a memory;

based on a time period for which the data is expected to be stored in the memory, characterizing the data;

based on characterizing the data, determining whether to use wear-leveling to store the data in the memory;

in response to determining to use wear-leveling to store the data in the memory,

(i) using wear-leveling to select a first memory block of the memory, and

(ii) storing the data in the selected first memory block of the memory; and

in response to determining to not use wear-leveling to store the data in the memory, refraining from using wear-leveling while storing the data in the memory.

2. The method of claim 1, wherein:

characterizing the data further comprises

based on the time period for which the data is expected to be stored in the memory, characterizing the data in one of a plurality of categories; and

determining whether to use wear-leveling to store the data in the memory further comprises

in response to the data being characterized in a first category of the plurality of categories, determining to not use wear-leveling to store the data in the memory, and

in response to the data being characterized in a second category of the plurality of categories, determining to use wear-leveling to store the data in the memory.

3. The method of claim 1, wherein characterizing the data further comprises:

in response to determining that the data is expected to be stored in the memory for more than a first threshold period of time, characterizing the data in a first category of a plurality of categories.

4. The method of claim 3, wherein determining whether to use wear-leveling to store the data in the memory further comprises:

in response to characterizing the data in the first category of the plurality of categories, determining to not use wear-leveling to store the data in the memory.

5. The method of claim 3, wherein characterizing the data further comprises:

in response to determining that the data is expected to be stored in the memory for less than a second threshold period of time, characterizing the data in a second category of the plurality of categories,

wherein the second threshold period of time is less than the first threshold period of time.

6. The method of claim 5, wherein determining whether to use wear-leveling to store the data in the memory further comprises:

in response to characterizing the data in the second category of the plurality of categories, determining to use wear-leveling to store the data in the memory.

7. The method of claim 5, wherein characterizing the data further comprises:

in response to determining that the data is expected to be stored in the memory for (i) more than the second threshold period of time and (ii) less than the first threshold period of time, characterizing the data in a third category of the plurality of categories.

8. The method of claim 1, wherein the memory is partitioned in a plurality of regions, and wherein the method further comprises:

in response to determining to not use wear-leveling to store the data in the memory, storing the data in a second memory block of a first region of the plurality of regions of the memory, and

wherein using wear-leveling further comprises

in response to determining to use wear-leveling to store the data in the memory, using wear-leveling to select the first memory block from a second region of the plurality of regions of the memory.

9. The method of claim 1, further comprising:

partitioning the memory into a plurality of regions; and

based on characterizing the data, selecting a region of the plurality of regions of the memory to store the data.

10. The method of claim 9, wherein:

a first region of the plurality of regions of the memory is configured to store data having a first expected storage duration; and

a second region of the plurality of regions of the memory is configured to store data having a second expected storage duration.

11. The method of claim 1, wherein the memory is a non-volatile memory.

12. The method of claim 1, wherein the memory is a NAND flash memory.

13. A memory controller configured to control access to a memory, the memory controller configured to:

receive data to be stored to the memory;

based on a time period for which the data is expected to be stored in the memory, characterize the data;

based on characterizing the data, determine whether to use wear-leveling to store the data in the memory;

in response to determining to use wear-leveling to store the data in the memory,

(i) use wear-leveling to select a first memory block of the memory, and

(ii) store the data in the selected first memory block of the memory; and

in response to determining to not use wear-leveling to store the data in the memory, refrain from using wear-leveling while storing the data in the memory.

14. The memory controller of claim 13, wherein:

the memory controller is configured to characterize the data by

based on the time period for which the data is expected to be stored in the memory, characterizing the data in one of a plurality of categories; and

the memory controller is configured to determine whether to use wear-leveling to store the data in the memory by

in response to the data being characterized in a first category of the plurality of categories, determining to not use wear-leveling to store the data in the memory, and

in response to the data being characterized in a second category of the plurality of categories, determining to use wear-leveling to store the data in the memory.

15. The memory controller of claim 13, wherein the memory controller is configured to characterize the data by:

in response to determining that the data is expected to be stored in the memory for more than a first threshold period of time, characterizing the data in a first category of a plurality of categories; and

in response to determining that the data is expected to be stored in the memory for less than a second threshold period of time, characterizing the data in a second category of the plurality of categories,

wherein the second threshold period of time is less than the first threshold period of time.

16. The memory controller method of claim 15, wherein the memory controller is configured to determine whether to use wear-leveling to store the data in the memory by:

in response to characterizing the data in the first category of the plurality of categories, determining to not use wear-leveling to store the data in the memory; and

in response to characterizing the data in the second category of the plurality of categories, determining to use wear-leveling to store the data in the memory.

17. The memory controller of claim 15, wherein the memory controller is further configured to characterize the data by:

in response to determining that the data is expected to be stored in the memory for (i) more than the second threshold period of time and (ii) less than the first threshold period of time, characterizing the data in a third category of the plurality of categories.

18. The memory controller of claim 13, wherein the memory controller is further configured to:

partition the memory into a plurality of regions; and

based on characterizing the data, select a region of the plurality of regions of the memory to store the data.

19. The memory controller of claim 13, wherein the memory is a non-volatile memory.

20. The memory controller of claim 13, wherein the memory is a NAND flash memory.