Temperature dependent refresh read rate
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.
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 defined time period increases as the current temperature decreases and the defined time period decreases as the current temperature increases.