Temperature dependent refresh read rate

Patent metadata

Field	Value
Publication number	US-12374379-B2
Application number	US-202318358463-A
Country	US
Kind code	B2
Filing date	Jul 25, 2023
Priority date	May 25, 2023
Publication date	Jul 29, 2025
Grant date	Jul 29, 2025

Abstract

Systems and methods for effecting a temperature dependent refresh read rate of a read operation of a block or sub-block of memory cells in a NAND string. The method includes initiating a refresh read cycle, determining a current temperature of the non-volatile memory device, and determining a refresh read rate corresponding to the current temperature. The refresh read is performed. The method further includes implementing a delay of a defined time period after the refresh read is performed, wherein the defined time period is based on the determined refresh read rate. If a new command is received before the delay has ended then the new command is performed, and if the delay has ended without a new command having been received then the method returns to the step of determining the current temperature.

First claim

What is claimed is:

1. A method for performing a refresh read in a non-volatile memory device, comprising:
initiating a refresh read cycle;
determining a current temperature of the non-volatile memory device;
determining a refresh read rate corresponding to the current temperature;
performing the refresh read;
implementing a delay of a defined time period after the refresh read is performed, wherein the defined time period is based on the determined refresh read rate;
when a new command is received before the delay has ended then perform the new command; and
when the delay has ended without a new command having been received then return to the step of determining the current temperature.

2. The method of claim 1 , wherein the step of determining the current temperature includes:
acquiring a temperature code from the non-volatile memory device;
relating the temperature code to a corresponding temperature using a first table stored in a memory of the non-volatile memory device, the first table relating a plurality of temperature codes to respective corresponding temperatures; and
identifying the corresponding temperature as the current temperature.

3. The method of claim 1 , wherein the step of determining the refresh read rate corresponding to the current temperature includes:
acquiring a temperature code from the non-volatile memory device that corresponds to the current temperature;
relating the temperature code to a corresponding refresh read rate using a second table stored in a memory of the non-volatile memory device, the second table relating a plurality of temperature codes to respective corresponding refresh read rates; and
identifying the corresponding refresh read rate as the refresh read rate.

4. The method of claim 1 , wherein the refresh read rate is faster as the current temperature increases and the refresh read rate is slower as the current temperature decreases.

5. The method of claim 1 , wherein the defined time period increases as the current temperature decreases and the defined time period decreases as the current temperature increases.

6. The method of claim 1 , wherein the step of determining a refresh read rate corresponding to the current temperature includes determining a point on a curve that plots a plurality of refresh rates vs. a plurality of corresponding temperatures.

7. The method of claim 1 , wherein the new command is a new read command.

8. A non-volatile memory device performing the method of claim 1 .

9. An apparatus, comprising:
a control circuit, configured to perform a refresh read in a non-volatile memory device, wherein to perform the refresh read, the control circuit is configured to perform the following operations:
initiate a refresh read cycle;
determine a current temperature of the non-volatile memory device;
determine a refresh read rate corresponding to the current temperature;
perform the refresh read;
implement a delay of a defined time period after the refresh read is performed, wherein the defined time period is based on the determined refresh read rate; and
when a new command is received before the delay has ended, perform the new command; and
when the delay has ended without a new command having been received, return to the operation of determining the current temperature.

10. The apparatus of claim 9 , wherein to determine the current temperature of the non-volatile memory device the control circuit is further configured to:
acquire a temperature code from the non-volatile memory device;
relate the temperature code to a corresponding temperature using a first table stored in a memory of the non-volatile memory device, the first table relating a plurality of temperature codes to respective corresponding temperatures; and
identify the corresponding temperature as the current temperature.

11. The apparatus of claim 9 , wherein to determine the refresh read rate corresponding to the current temperature, the control circuit is further configured to:
acquire a temperature code from the non-volatile memory device that corresponds to the current temperature;
relate the temperature code to a corresponding refresh read rate using a second table stored in a memory of the non-volatile memory device, the second table relating a plurality of temperature codes to respective corresponding refresh read rates; and
identify the corresponding refresh read rate as the refresh read rate.

12. The apparatus of claim 9 , wherein the refresh read rate is faster as the current temperature increases and the refresh read rate is slower as the current temperature decreases.

13. The apparatus of claim 9 , wherein the defined time period increases as the current temperature decreases and the defined time period decreases as the current temperature increases.

14. The apparatus of claim 9 , wherein to determine a refresh read rate corresponding to the current temperature, the control circuit is further configured to determine a point on a curve that plots a plurality of refresh rates vs. a plurality of corresponding temperatures.

15. The apparatus of claim 9 , wherein the new command is a new read command.

16. A non-transitory computer-readable storage medium comprising instructions executable by a processor, the instructions programming the processor to perform a refresh read in a non-volatile memory device; wherein to perform the refresh read, the instructions programming the processor to:
initiate a refresh read cycle;
determine a current temperature of the non-volatile memory device;
determine a refresh read rate corresponding to the current temperature;
perform the refresh read;
implement a delay of a defined time period after the refresh read is performed, wherein the defined time period is based on the determined refresh read rate;
when a new command is received before the delay has ended then perform the new command; and
when the delay has ended without a new command having been received then return to the step of determining the current temperature.

17. The non-transitory computer-readable storage medium of claim 16 , wherein the instruction of determining the current temperature includes further programming the processor to:
acquire a temperature code from the non-volatile memory device;
relate the temperature code to a corresponding temperature using a first table stored in a memory of the non-volatile memory device, the first table relating a plurality of temperature codes to respective corresponding temperatures; and
identify the corresponding temperature as the current temperature.

18. The non-transitory computer-readable storage medium of claim 16 wherein the instruction of determining the refresh read rate corresponding to the current temperature includes: further programming the processor to:
acquire a temperature code from the non-volatile memory device that corresponds to the current temperature;
relate the temperature code to a corresponding refresh read rate using a second table stored in a memory of the non-volatile memory device, the second table relating a plurality of temperature codes to respective corresponding refresh read rates; and
identify the corresponding refresh read rate as the refresh read rate.

19. The non-transitory computer-readable storage medium of claim 16 , wherein the refresh read rate is faster as the current temperature increases and the refresh read rate is slower as the current temperature decreases.

20. The non-transitory computer-readable storage medium of claim 16 , wherein the define

Assignees

• Western Digital Tech Inc

Inventors

• Wang Yanzhen
• Ganji Mahdi
• Wang Yanjie

Classifications

• G11C11/40615

  Internal triggering or timing of refresh, e.g. hidden refresh, self refresh, pseudo-SRAMs · CPC title

• G11C11/4076 Primary

  Timing circuits (for regeneration management G11C11/406) · CPC title

• G11C11/40626 Primary

  Temperature related aspects of refresh operations · CPC title