Granted Patent B2

US 12,306,710 · App. 18/449,491 · Granted May 20, 2025

Inventors: Pradeep Hegde (Bangalore, IN); Akhilesh Yadav (Bangalore, IN); Shivam Mishra (Bangalore, IN)

Assignee: Sandisk Technologies, Inc.

G06F11/10

Abstract

Claims (67)

1. A device, comprising:

a memory interface configured to interface with a non-volatile memory; and

a controller configured to:

select a metablock of the non-volatile memory for programming,

program the metablock, wherein programming the metablock includes assigning the metablock to one of a plurality of thermal region tags (“TRTs”) associated with a respective one of a plurality of thermal regions, and each TRT of the plurality of TRTs is associated with a respective set of read parameters,

perform a periodic TRT update to detect a room temperature data retention (“RTDR”) phenomena associated with the metablock, wherein the periodic TRT update includes:

determining a bit error rate (“BER”) associated with the metablock,

determining a change in the BER from a previously determined BER associated with the metablock,

in response to determining that a temporal threshold associated with a period of time after programming of the metablock has been exceeded, updating a counter based on the change in the BER from the previously determined BER,

determining whether the counter exceeds a count threshold associated with detection of a RTDR phenomena, and

in response to determining that the count threshold associated with the detection of a RTDR phenomena has been exceeded, reassigning the metablock to a different one of the plurality of TRTs associated with a respective different one of the plurality of thermal regions; and

in response to receiving a read request for the metablock from an external electronic device, read the metablock using the respective set of read parameters associated with the TRT to which the metablock is assigned.

2. The device of claim 1 ,

wherein the temporal threshold corresponds to a shift in a cell voltage distribution (“CVD”) of the metablock.

3. The device of claim 2 , wherein, to update the counter based on the change in the BER from the previously determined BER, the controller is further configured to:

determine whether the change in the BER from the previously determined BER exceeds a BER change threshold, and

in response to determining that the change in the BER from the previously determined BER exceeds the BER change threshold, increment the counter.

4. The device of claim 2 , wherein to determine whether the temporal threshold has been exceeded, the controller is further configured to:

determine a function of the change in the BER of the metablock over time,

determine a first derivative of the function,

determine a second derivative of the function, and

determine whether a local maximum of the second derivative has occurred, wherein the local maximum is indicative of the temporal threshold.

5. The device of claim 4 , wherein the function is a function f(x) defined as: f(x)=1/(1+exp (−a*x)), where ‘a’ is a constant indicative of a periodic change in BER of the metablock, and ‘x’ is elapsed time.

6. The device of claim 2 , wherein to determine whether the temporal threshold has been exceeded, the controller is further configured to:

determine an amount of time elapsed since a programming of the metablock, and

determine whether the amount of time elapsed since the programming of the metablock has exceeded the temporal threshold, wherein the temporal threshold is a predetermined value.

7. The device of claim 6 , wherein the temporal threshold is stored in a lookup table (“LUT”).

8. A method performed by a data storage device, the method comprising:

selecting a metablock of a non-volatile memory for programming;

programing the metablock, wherein programming the metablock includes assigning the metablock to one of a plurality of thermal region tags (“TRTs”) associated with a respective one of a plurality of thermal regions, and each TRT of the plurality of TRTs is associated with a respective set of read parameters;

performing a periodic TRT update to detect a room temperature data retention (“RTDR”) phenomena associated with the metablock, wherein performing the periodic TRT update includes:

determining a bit error rate (“BER”) associated with the metablock,

determining a change in the BER from a previously determined BER associated with the metablock,

in response to determining that a temporal threshold associated with a period of time after programming of the metablock has been exceeded, updating a counter based on the change in the BER from the previously determined BER,

determining whether the counter exceeds a count threshold associated with detection of a RTDR phenomena, and

in response to determining that the count threshold associated with the detection of a RTDR phenomena has been exceeded, reassigning the metablock to a different one of the plurality of TRTs associated with a respective different one of the plurality of thermal regions; and

in response to receiving a read request for the metablock from an external electronic device, reading the metablock using the respective set of read parameters associated with a TRT to which the metablock is assigned.

9. The method of claim 8 , wherein

the temporal threshold corresponds to a shift in a cell voltage distribution (“CVD”) of the metablock.

10. The method of claim 9 , wherein updating the counter based on the change in the BER from the previously determined BER includes:

determining whether the change in the BER from the previously determined BER exceeds a BER change threshold, and

in response to determining that the change in the BER from the previously determined BER exceeds the BER change threshold, incrementing the counter.

11. The method of claim 9 , wherein determining whether the temporal threshold has been exceeded includes:

determining a function of the change in the BER of the metablock over time,

determining a first derivative of the function,

determining a second derivative of the function, and

determining whether a local maximum of the second derivative has occurred, wherein the local maximum is indicative of the temporal threshold.

12. The method of claim 11 , wherein the function is a function f(x) defined as: f(x)=1/(1+exp (−a*x)), where ‘a’ is a constant indicative of a periodic change in BER of the metablock, and ‘x’ is elapsed time.

13. The method of claim 9 , wherein determining whether the temporal threshold has been exceeded includes:

determining an amount of time elapsed since a programming of the metablock, and

determining whether the amount of time elapsed since the programming of the metablock has exceeded the temporal threshold, wherein the temporal threshold is a predetermined value.

14. The method of claim 13 , wherein the temporal threshold is stored in a lookup table (“LUT”).

15. An apparatus comprising:

means for selecting a metablock of a non-volatile memory for programming;

means for programing the metablock, wherein programming the metablock includes assigning the metablock to one of a plurality of thermal region tags (“TRTs”) associated with a respective one of a plurality of thermal regions, and each TRT of the plurality of TRTs is associated with a respective set of read parameters;

means for performing a periodic TRT update to detect a room temperature data retention (“RTDR”) phenomena associated with the metablock, wherein performing the periodic TRT update includes:

determining a bit error rate (“BER”) associated with the metablock,

determining a change in the BER from a previously determined BER associated with the metablock,

in response to determining that a temporal threshold associated with a period of time after programming of the metablock has been exceeded, updating a counter based on the change in the BER from the previously determined BER, and

determining whether the counter exceeds a count threshold associated with detection of a RTDR phenomena; and

in response to determining that the count threshold associated with the detection of a RTDR phenomena has been exceeded, reassigning the metablock to a different one of the plurality of TRTs associated with a respective different one of the plurality of thermal regions; and

means for, in response to receiving a read request for the metablock from an external electronic device, reading the metablock using the respective set of read parameters associated with a TRT to which the metablock is assigned.

16. The apparatus of claim 15 , wherein

the temporal threshold corresponds to a shift in a cell voltage distribution (“CVD”) of the metablock.

17. The apparatus of claim 16 , wherein updating the counter based on the change in the BER from the previously determined BER includes:

determining whether the change in the BER from the previously determined BER exceeds a BER change threshold, and

in response to determining that the change in the BER from the previously determined BER exceeds the BER change threshold, incrementing the counter.

Assignments (8)

Continuity (2)

References Cited (12)