TEMPERATURE ALERT AND LOW RATE REFRESH FOR A NON-VOLATILE MEMORY

• US 20120033519A1
• Filed: 12/30/2008
• Published: 02/09/2012
• Est. Priority Date: 12/30/2008
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Confalonieri, Emanuele, Balluchi, Daniele
• Granted Patent: US 8,762,656 B2
• Time in Patent Office: Days
• US Class Current: 365/222
• CPC Class Codes: G11C 13/0004 comprising amorphous/crystalline phase transition cells
• CPC Class Codes: G11C 13/0033 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
• CPC Class Codes: G11C 7/04 with means for avoiding disturbances due to temperature effects

Abstract

A method and apparatus are described for measuring a temperature within a non-volatile memory, storing, in a register within the non-volatile memory, a temperature alert comprising one or more bits indicating the non-volatile memory has exceeded a threshold temperature for a period of time, determining, by a host, that the temperature alert is active, and in response to the determination that the temperature alert is active, refreshing at least a portion of the non-volatile memory.

Claims

1. An apparatus comprising:

a non-volatile memory including

a temperature sensor to measure a temperature within the non-volatile memory and

a register to store a temperature alert comprising one or more bits indicating the non-volatile memory has exceeded a threshold temperature for a period of time; and

a controller to determine that the temperature alert is active and, in response to determining that the temperature alert is active, refresh at least a portion of the non-volatile memory.

2. The apparatus of claim 1, wherein the temperature alert indicates one of a plurality of levels of urgency for the refresh.

3. The apparatus of claim 1, wherein the refresh of at least a portion of the non-volatile memory is performed at a predetermined level of granularity.

4. The apparatus of claim 3, wherein the predetermined level of granularity is configured by a user.

5. The apparatus of claim 3, wherein the register indicates whether or not each of a plurality of portions of the non-volatile memory needs to be refreshed.

6. The apparatus of claim 1, wherein the non-volatile memory further includes a refresh mask register to indicate whether or not a portion of the non-volatile memory may undergo a refresh.

7. The apparatus of claim 1, wherein an amount of time the temperature exceeds the threshold temperature is tracked in two or more levels of granularity.

8. The apparatus of claim 1, wherein a rate at which the controller refreshes at least a portion of the non-volatile memory increases corresponding to an increase in temperature beyond the threshold temperature.

9. The apparatus of claim 1, wherein the temperature alert is set when an integral of the temperature during a time period when the temperature exceeds a threshold temperature exceeds a threshold value.

10. The apparatus of claim 9, wherein the non-volatile memory maintains a sum of the integral of the temperature during multiple time periods when the temperature exceeds the threshold temperature and the temperature alert is set when the sum of the integrals exceeds the threshold value.

11. A method comprising:

measuring a temperature within a non-volatile memory;

storing, in a register within the non-volatile memory, a temperature alert comprising one or more bits indicating the non-volatile memory has exceeded a threshold temperature for a period of time;

determining, by a controller, that the temperature alert is active; and

in response to the determination that the temperature alert is active, refreshing at least a portion of the non-volatile memory.

12. The method of claim 11, wherein the temperature alert indicates one of a plurality of levels of urgency for the refresh.

13. The method of claim 11, wherein the refresh of at least a portion of the non-volatile memory is performed at a predetermined level of granularity.

14. The method of claim 13, wherein the predetermined level of granularity is configured by a user.

15. The method of claim 13, further comprising:

storing, in a register within the non-volatile memory, a refresh status to indicate whether or not each of a plurality of portions of the non-volatile memory needs to be refreshed.

16. The method of claim 11, further comprising:

storing, in a register within the non-volatile memory, a refresh mask register to indicate whether or not a portion of the non-volatile memory may undergo a refresh.

17. The method of claim 11, wherein an amount of time the temperature exceeds the threshold temperature is tracked in two or more levels of granularity.

18. The method of claim 11, further comprising:

setting the temperature alert to active when an integral of the temperature during a time period when the temperature exceeds a threshold temperature exceeds a threshold value.

19. The method of claim 19, further comprising:

storing, in the non-volatile memory, a sum of the integral of the temperature during multiple time periods when the temperature exceeds the threshold temperature; and

setting the temperature alert to active when the sum of the integrals exceeds the threshold value.

20. An apparatus comprising:

a non-volatile memory including a reference memory cell to indicate memory degradation; and

a controller to determine if the reference memory cell has degraded and, in response to determining that the reference memory cell has degraded, refresh at least a portion of the non-volatile memory.