Methods of end of life calculation for non-volatile memories

• US 7,523,013 B2
• Filed: 05/15/2006
• Issued: 04/21/2009
• Est. Priority Date: 05/15/2006
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Conley, Kevin M., Gorobets, Sergey Anatolievich
• Primary Examiner(s): Feliciano; Eliseo Ramos
• Assistant Examiner(s): Suarez; Felix E
• Application Number:
  US11/383,384
• Publication Number:
  US 20070266200A1
• Time in Patent Office: 1,072 Days
• Field of Search: 702/22, 702/33, 702/34, 702/63, 702/106, 702/127, 702/166, 702/176, 702/177, 702/179, 702/182, 365/236, 438/3, 711/107
• US Class Current: 702/177
• CPC Class Codes: G06F 11/008 Reliability or availability analysis
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles
• CPC Class Codes: G11C 16/3495 Circuits or methods to detect or delay wearout of nonvolatile EPROM or EEPROM memory devices, e.g. by counting numbers of erase or reprogram cycles, by using multiple memory areas serially or cyclically

Abstract

A system and methods are given for providing information on the amount of life remaining for a memory having a limited lifespan, such as a flash memory card. For example, it can provide a user with the amount of the memory'"'"'s expected remaining lifetime in real time units (i.e., hours or days) or as a percentage of estimated initial life. An end of life warning can also be provided. In a particular embodiment, the amount of remaining life (either as a percentage or in real time units) can be based on the average number of erases per block, but augmented by the number of spare blocks or other parameters, so that an end of life warning is given if either the expected amount of remaining life falls below a certain level or the number of spare blocks falls below a safe level.

Claims

1. A method of operating a memory system having a plurality of rewritable memory cells, comprising:

operating the memory system over a period of time;

maintaining a parameter indicative of the number of rewrites the memory cells undergo during said period of time;

providing an indication of the expected amount of remaining lifetime of the memory system based on the value of said parameter indicative of the number of rewrites the memory cells;

subsequent to providing said indication of the expected amount of remaining lifetime, further operating the memory system;

monitoring the usage pattern of the memory system during said further operating the memory system; and

adjusting the expected amount of remaining lifetime of the memory system based on said usage pattern.

2. The method of claim 1, wherein said monitoring the usage pattern is performed using a system clock of the memory system.

3. The method of claim 1, wherein the memory system is attached to a host and wherein said monitoring the usage pattern is performed using a clock value from the host.

4. A method of operating a memory system having a plurality of rewritable memory cells, comprising:

operating the memory system over a period of time;

maintaining a parameter indicative of the number of rewrites the memory cells undergo during said period of time; and

providing an indication of the expected amount of remaining lifetime of the memory system based on the value of said parameter indicative of the number of rewrites the memory cells,

wherein the memory system is attached to a host and wherein the expected amount of remaining lifetime of the memory system is additionally based on the host'"'"'s peak write rate to the memory system.

5. A method of operating a memory system having a plurality of rewritable memory cells, comprising:

operating the memory system over a period of time;

maintaining a parameter indicative of the number of rewrites the memory cells undergo during said period of time; and

providing an indication of the expected amount of remaining lifetime of the memory system based on the value of said parameter indicative of the number of rewrites the memory cells,

wherein the rewrite process of the memory cells includes being erased prior to data content being rewritten and said parameter is average number of erases to which the memory cells have been subjected.

6. A method of operating a memory system having a plurality of rewritable memory cells, comprising:

operating the memory system over a period of time;

maintaining a parameter indicative of the number of rewrites the memory cells undergo during said period of time; and

providing an indication of the expected amount of remaining lifetime of the memory system based on the value of said parameter indicative of the number of rewrites the memory cells,

wherein said parameter is a cyclic wear leveling pointer.

7. A method operating a memory system having a plurality of rewritable memory cells, comprising:

operating the memory system over a period of time;

maintaining a parameter indicative of the number of rewrites the memory cells undergo during said period of time; and

providing an indication of the expected amount of remaining lifetime of the memory system based on the value of said parameter indicative of the number of rewrites the memory cells,

wherein the indication of the expected amount of remaining lifetime is provided as a percentage of total expected lifetime of the memory system.

8. A method of operating a memory system having a plurality of rewritable memory cells, comprising:

operating the memory system over a period of time;

maintaining a parameter indicative of the number of rewrites the memory cells undergo during said period of time; and

providing an indication of the expected amount of remaining lifetime of the memory system based on the value of said parameter indicative of the number of rewrites the memory cells,

wherein the indication of the expected amount of remaining lifetime is provided in units of real time.

9. The method of claim 8, wherein the providing an indication of the expected amount of remaining lifetime includes using a system clock of the memory system to calculate the expected lifetime in units of real time.

10. The method of claim 8, wherein the memory system is attached to a host and wherein the providing an indication of the expected amount of remaining lifetime includes using a clock value front the host to calculate the expected lifetime in units of real time.

11. The method of claim 10, wherein the indication of the expected amount of remaining lifetime of the memory system is provided to the host in response to a command form the host that includes said clock value.

12. A method of operating a memory system having a plurality of rewritable memory cells, comprising:

operating the memory system over a period of time;

maintaining a parameter indicative of the number of rewrites the memory cells undergo during said period of time; and

providing an indication of the expected amount of retaining lifetime of the memory system based on the value of said parameter indicative of the number of rewrites the memory cells,

wherein, in response to the expected amount of remaining lifetime reaching a predetermined value, the memory changes operating behavior.

13. The method of claim 12, wherein in response to the expected amount of remaining lifetime reaching a predetermined value, the memory operates in a read only mode.

14. The method of claim 12, wherein in response to the expected amount of remaining lifetime reaching a predetermined value, the memory changes an operation speed.

15. The method of claim 12, wherein in response to the expected amount of remaining lifetime reaching a predetermined value, the memory changes memory block usage.

16. A method of operating a system including a host and a memory system for use with the host and having a plurality of rewritable memory cells, the method comprising:

operating the memory system over a period of time;

maintaining on the memory system a parameter indicative of the number of rewrites the memory cells undergo during said period of time;

providing from the memory system to the host an indication of the expected amount of remaining lifetime of the memory system based on the value of said parameter indicative of the number of rewrites the memory cells; and

providing status of said indication of the expected amount of remaining lifetime of the memory system to a user of the host,

wherein said status is provided as a status bar display.

17. A method of operating a system including a host and a memory system for use with the host and having a plurality of rewritable memory cells, the method comprising:

operating the memory system over a period of time;

maintaining on the memory system a parameter indicative of the number of rewrites the memory cells undergo during said period of time;

providing from the memory system to the host an indication of the expected amount of remaining lifetime of the memory system based on the value of said parameter indicative of the number of rewrites the memory cells;

subsequent to providing said indication of the expected amount of remaining lifetime to the host, further operating the memory system;

monitoring the usage pattern of the memory system during said further operating the memory system; and

adjusting the expected amount of remaining lifetime of the memory system based on said usage pattern.

18. The method of claim 17, wherein said monitoring the usage pattern is performed using a system clock of the memory system.

19. The method of claim 17, wherein said monitoring the usage pattern is performed using a clock value from the host.

20. A method of operating a system including a host and a memory system for use with the host and having a plurality of rewritable memory cells, the method comprising:

operating the memory system over a period of time;

maintaining on the memory system a parameter indicative of the number of rewrites the memory cells undergo during said period of time; and

providing from the memory system to the host an indication of the expected amount of remaining lifetime of the memory system based on the value of said parameter indicative of the number of rewrites the memory cells,

wherein the expected amount of remaining lifetime of the memory system is additionally based on the host'"'"'s peak write rate to the memory system.

21. A method of operating a system including a host and a memory system for use with the host and having a plurality of rewritable memory cells, the method comprising:

operating the memory system over a period of time;

maintaining on the memory system a parameter indicative of the number of rewrites the memory cells undergo during said period of time; and

providing from the memory system to the host an indication of the expected amount of remaining lifetime of the memory system based on the value of said parameter indicative of the number of rewrites the memory cells,

wherein the indication of the expected amount of remaining lifetime is provided in units of real time.

22. The method of claim 21, wherein the providing an indication of the expected amount of remaining lifetime includes using a system clock of the memory system to calculate the expected lifetime in units of real time.

23. The method of claim 21, wherein the providing an indication of the expected amount of remaining lifetime includes using a clock value from the host to calculate the expected lifetime in units of real time.

24. The method of claim 23, wherein the indication of the expected amount of remaining lifetime of the memory system is provided to the host in response to a command form the host that includes said clock value.

25. The method of claim 24, wherein the providing an indication of the expected amount of remaining lifetime to the host includes providing a warning to the host if the expected amount of remaining lifetime reaches a predetermined value.

26. The method of claim 25, further comprising:

providing an indication of said warning to a user of the host.

27. The method of claim 25, further comprising:

the host passing said warning to one or more applications on the host.

28. The method of claim 27, further comprising:

shutting down one or more of said applications in response to said warning.

29. The method of claim 25, further comprising:

in response to said warning, the host activating a back-up process.

30. The method of claim 25, further comprising:

the host shutting down in response to said warning.

31. A method of operating a memory system for use with a host and having a plurality of rewritable memory cells, comprising:

operating the memory system over a first period of time;

maintaining a parameter indicative of the wear of the memory cells during said first period of time;

determining an expected amount of remaining lifetime of the memory system based on the value of said parameter indicative of the wear of the memory cells during said first period of time;

subsequently operating the memory system over a second period of time;

maintaining the parameter indicative of the wear of the memory cells during said second period of time; and

revising the expected amount of remaining lifetime of the memory system based on the value of said parameter indicative of the wear of the memory cells during said second period of time.

32. The method of claim 31, wherein the memory system is detachably connectable to the host.

33. The method of claim 31, wherein the memory system is an embedded memory system.

34. The method of claim 31, wherein said parameter indicative of the wear of the memory cells is the number of rewrites the memory cells undergo during said periods of time.

35. The method of claim 31, wherein said parameter indicative of the wear of the memory cells is the block failure rate during said periods of time.

36. The method of claim 31, wherein said parameter indicative of the wear of the memory cells is an indication of data error during said periods of time.

37. The method of claim 36, wherein said indication of data error are the magnitude and frequency ECC corrections.

38. The method of claim 31, wherein said parameter indicative of the wear of the memory cells are program times during said periods of time.

39. The method of claim 31, wherein said parameter indicative of the wear of the memory cells are erase times during said periods of time.

40. The method of claim 31, wherein the memory cells are physically arranged into a plurality of physical erase structures, the method further comprising monitoring the number of spare erase structures, wherein the expected amount of remaining lifetime of the memory system is additionally based on the number of spare erase structures.

41. The method of claim 31, wherein the memory cells are physically arranged into a plurality of physical erase structures and said parameter indicative of the wear of the memory cells is the number of spare erase structures.

42. The method of claim 31, further comprising:

monitoring the usage pattern of the memory system during said time periods, wherein said

revising the expected amount of remaining lifetime of the memory system is additionally based on said usage pattern.

43. The method of claim 42, wherein said monitoring the usage pattern is performed using a system clock of the memory system.

44. The method of claim 42, wherein the memory system is attached to the host and wherein said monitoring the usage pattern is performed using a clock value from the host.

45. The method of claim 31, further comprising providing a warning if the parameter indicative of the wear of the memory cells reaches a predetermined value.

46. The method of claim 31, wherein the memory system is attached to the host and wherein the expected amount of remaining lifetime of the memory system is additionally based on the host'"'"'s peak write rate to the memory system.

47. The method of claim 31, wherein an indication of the expected amount of remaining lifetime is provided as a percentage of total expected lifetime of the memory system.

48. The method of claim 31, wherein an indication of the expected amount of remaining lifetime is provided in units of real time.

49. The method of claim 48, wherein the revising the expected amount of remaining lifetime includes using a system clock of the memory system to calculate the expected lifetime in units of real time.

50. The method of claim 48, wherein the memory system is attached to the host and wherein the revising of the expected amount of remaining lifetime includes using a clock value from the host to calculate the expected lifetime in units of real time.

51. The method of claim 50, wherein the expected amount of remaining Lifetime of the memory system is provided to the host in response to a command form the host that includes said clock value.

52. The method of claim 31, wherein the revising of the expected amount of remaining lifetime includes providing a warning if the expected amount of remaining lifetime reaches a predetermined value.

53. The method of claim 31, further comprising, in response to the expected amount of remaining lifetime reaching a predetermined value, the memory changes operating behavior.

54. The method of claim 53, wherein in response to the expected amount of remaining lifetime reaching a predetermined value, the memory operates in a read only mode.

55. The method of claim 53, wherein in response to the expected amount of remaining lifetime reaching a predetermined value, the memory changes an operation speed.

56. The method of claim 53, wherein in response to the expected amount of remaining lifetime reaching a predetermined value, the memory changes memory block usage.

57. A method of operating one or more memory devices and a host to which the one or more memory devices are connectable, the method comprising:

attaching a first of the memory devices to the host;

operating the first memory device during a period of time while attached to the host;

while said first memory device is operating, sending from the host to the first memory device a plurality of first current time values;

while said first memory device is operating, maintaining on the first memory device a usage rate for the first memory device; and

determining on the first memory device an indication of remaining life of the first memory device in real time units based on said plurality of first current time values and the usage rate for the first memory device.

58. The method of claim 57, further comprising:

sending the indication of remaining life of the first memory device in real time units to the host.

59. The method of claim 58, wherein the memory device sends the indication of remaining life of the first memory device in real time units to the host in response to a command from the host that also includes the sending of one of said plurality of first current time values.

60. The method of claim 57, further comprising:

during said period of time, detaching from and reattaching to the host of said first memory device.

61. The method of claim 57, further comprising:

during said period of time, attaching a second of the memory devices to the host;

operating the second memory device while attached to the host;

while said second memory device is operating, sending from the host to the second memory device a plurality of second current time values;

while said second memory device is operating, maintaining on the second memory device a usage rate for the second memory device; and

determining on the second memory device an indication of remaining life of the second memory device in real time units based on said plurality of second current time values and the usage rate for the second memory device.

62. The method of claim 57, wherein each of the memory devices has an associated ID by which the memory devices may be distinguished by the host.

63. The method of claim 57, further comprising:

during said period of time, monitoring by the of the usage pattern of said first memory device, wherein said usage pattern influences when the host sends to the first memory device one or more of said first current time values

64. The method of claim 57, wherein said method is supported by a host utility.

65. A method of operating one or more memory devices and a host to which the one or more memory devices are connectable, the method comprising:

attaching a first of the memory devices to the host;

operating the first memory device during a period of time while attached to the host;

while said first memory device is operating, maintaining on the first memory device a wear level for the first memory device;

sending from the first memory device to the host the value of the wear level of the first memory device at a plurality of first current time values; and

determining on the host an indication of remaining life of the first memory device in real time units based on said plurality of first current time values and the wear level values for the first memory device.

66. The method of claim 65, wherein the memory device sends the value of the wear level at the plurality of first current time values to the host in response to a command from the host.

67. The method of claim 65, further comprising:

during said period of time, detaching from and reattaching to the host of said first memory device.

68. The method of claim 65, further comprising:

during said period of time, attaching a second of the memory devices to the host;

operating the second memory device while attached to the host;

while said second memory device is operating, maintaining on the second memory device a wear level for the second memory device;

sending from the second memory device to the host the value of the wear level for the second memory device at a plurality of second current time values; and

determining on the host an indication of remaining life of the second memory device in real time units based on said plurality of second current time values and the wear level values for the second memory device.

69. The method of claim 68, wherein each of the memory devices has an associated ID by which the memory devices may be distinguished by the host.

70. The method of claim 65, wherein said method is supported by a host utility.