Wordline-to-wordline stress configuration
A method and system for performing wordline-to-wordline stress routines on a storage device is disclosed. Stress routines may be performed to reduce state widening in multi-level memory cells in the storage device. However, data retention problems may result if the stress routines are performed too often. In order to perform the stress routines at the proper times, a stress control variable is used. The stress control variable may be indicative of age of the storage device (such as the number of erase cycles performed on a memory block in the storage device). The stress control variable is input to a look-up table (or other logical construct), with the output of the look-up table indicating whether to perform the wordline-to-wordline stress routine. In this way, the stress routines may be performed to reduce state widening while reducing the ill effects of data retention.
1. A method for determining whether to perform a stress routine in a storage device, the method comprising:
accessing a stress control variable, the stress control variable indicative of use or reliability of at least a part of the storage device;
determining whether to perform the stress routine, wherein determining whether to perform the stress routine is varied based on the stress control variable; and
if it is determined to perform the stress routine, performing the stress routine.
2. The method of claim 1 , wherein a frequency of performing the stress routine when the stress control variable indicates less use of the storage device is lower than a frequency of performing the stress routine when the stress control variable indicates greater use of the storage device.
3. The method of claim 1 , wherein the stress routine comprises a wordline-to-wordline stress routine.
4. The method of claim 3 , wherein the stress control variable is indicative of a leakage current from wordline-to-wordline.
5. The method of claim 1 , wherein determining whether to perform the stress routine is based on a logical construct correlating the stress control variable with the determination whether to perform the stress routine.
6. The method of claim 1 , wherein the stress control variable is indicative of a number of erase cycles performed on one or more blocks during at least a part of operation of the storage device.
7. The method of claim 6 , wherein determining whether to perform the stress routine comprises:
determining to perform the stress routine every “X” erase cycles, where “X” is an integer.
8. The method of claim 6 , wherein the closer the number of erase cycles is to a rated number of erase cycles for the storage device, the less likely the stress routine is performed.
9. The method of claim 1 , wherein the stress control variable is indicative of an amount of leakage current between different wordlines.
10. The method of claim 9 , wherein the stress control variable indicating a higher amount of leakage current results in the stress routine being more likely performed than the stress control variable indicating a lower amount of leakage current.
11. A method for determining whether to perform a stress routine in a storage device, the method comprising:
accessing a stress control variable, the stress control variable indicative of at least one dynamic aspect of the storage device;
determining whether to perform the stress routine, wherein determining whether to perform the stress routine is varied based on the stress control variable; and
if it is determined to perform the stress routine, performing the stress routine,
wherein the stress control variable is indicative of a number of erase cycles performed on at least one block in the storage device.
12. A storage device comprising:
a memory; and
a controller in communication with the memory, the controller configured to:
access a stress control variable, the stress control variable indicative of use or reliability of at least a part of the storage device;
determine whether to perform the stress routine, wherein determining whether to perform the stress routine is varied based on the stress control variable; and
if it is determined to perform the stress routine, perform the stress routine.
13. The storage device of claim 12 , wherein the controller is configured to determine whether to perform the stress routine when the stress control variable indicates less use of the storage device at a lower frequency than determining whether to perform the stress routine when the stress control variable indicates greater use of the storage device.
14. The storage device of claim 12 , wherein the stress control variable is indicative of a number of erase cycles performed on at least one block in the storage device.
15. The storage device of claim 12 , wherein the stress routine comprises a wordline-to-wordline stress routine.
16. The storage device of claim 15 , wherein the stress control variable is indicative of a leakage current from wordline-to-wordline.
17. The storage device of claim 12 , wherein the controller is configured to determine whether to perform the stress routine based on a logical construct correlating the stress control variable with the determination whether to perform the stress routine.
18. The storage device of claim 12 , wherein the stress control variable is indicative of a number of erase cycles performed on one or more blocks during at least a part of operation of the storage device.
19. The storage device of claim 18 , wherein the controller is configured to determine whether to perform the stress routine by:
determining to perform the stress routine every “X” erase cycles, where “X” is an integer.
20. The storage device of claim 18 , wherein the closer the number of erase cycles is to a rated number of erase cycles for the storage device, the controller is less likely to perform the stress routine.
21. The storage device of claim 12 , wherein the stress control variable is indicative of an amount of leakage current between different wordlines.
22. The storage device of claim 21 , wherein the stress control variable indicating a higher amount of leakage current results in controller being more likely to perform the stress routine than the stress control variable indicating a lower amount of leakage current.