Granted Patent B2

US 8,644,099 · App. 13/179,466 · Granted Feb 4, 2014

Abstract

Claims (107)

1. A non-transitory machine-readable medium including machine-executable instructions stored thereon, which when executed by a machine or computer cause the machine or computer to perform a method of determining a dwell time in a memory circuit after a shutdown of the memory circuit, the method comprising:

storing a first test block before the shutdown;

storing a second test block after powering on the memory circuit;

performing a first read level sweep of the first test block to determine a first read level voltage with minimum errors, including determining the first read level voltage as a function of a nominal read level voltage and a first estimation parameter;

performing a second read level sweep of the second test block to determine a second read level voltage with minimum errors, including determining the second read level voltage as a function of the nominal read level voltage and a second estimation parameter;

determining a shutdown threshold voltage (V T ) shift as a function of the first read level voltage and the second read level voltage; and

determining a shutdown duration as a function of the shutdown V T shift.

2. The non-transitory machine-readable medium of claim 1 , the method further comprising:

reading a drive temperature after the drive temperature has stabilized;

determining a revised duration as a function of the shutdown duration and the drive temperature and a reference temperature; and

determining the dwell time as a function of a current time and a block time stamp and the revised duration.

3. The non-transitory machine-readable medium of claim 2 , wherein determining the revised duration as a function of the shutdown duration and the drive temperature and the reference temperature includes:

determining a temperature acceleration factor as a function of the drive temperature and the reference temperature; and

determining the revised duration as a function of the shutdown duration and the temperature acceleration factor.

4. The non-transitory machine-readable medium of claim 2 , the method further comprising:

storing a pre-shutdown temperature before the shutdown, wherein determining the dwell time as a function of the current time and the block time stamp and the revised duration includes:

retrieving the pre-shutdown temperature and the block time stamp after the memory circuit is powered on,

determining a temperature acceleration factor as a function of the drive temperature and the pre-shutdown temperature, and

determining the dwell time as a function of the current time, the block time stamp, the revised duration, and the temperature acceleration factor.

5. The non-transitory machine-readable medium of claim 4 , wherein determining the dwell time includes:

determining a temporary duration by subtracting the block time stamp from the current time; and

multiplying the temporary duration by the temperature acceleration factor and then adding the revised duration.

6. The non-transitory machine-readable medium of claim 1 , wherein determining a shutdown duration as a function of the shutdown V T shift includes indexing a lookup table by the shutdown V T shift and a program/erase cycle to retrieve the shutdown duration.

7. The non-transitory machine-readable medium of claim 1 , the method further comprising:

determining the dwell time as a function of a current time and a first block time stamp associated with a memory block and a temperature acceleration factor;

determining an updated block time stamp by subtracting the dwell time from a current time; and

storing the updated block time stamp.

8. The non-transitory machine readable medium of claim 1 , wherein storing the first test block includes:

writing data to a memory block; and

storing an address of the memory block.

9. The non-transitory machine-readable medium of claim 1 , the method further comprising:

determining a temperature acceleration factor as a function of a drive temperature;

determining a current aging time as a function of a current time value and the temperature acceleration factor;

determining an post-shutdown aging time as a function of the current aging time and the shutdown duration;

reading a block time stamp; and

determining the dwell time by subtracting the block time stamp from the post-shutdown aging time.

10. The non-transitory machine-readable medium of claim 1 , the method further comprising:

determining a temperature acceleration factor as a function of a drive temperature;

determining a current aging time as a function of a current time value and the temperature acceleration factor;

receiving a command representative of a write operation; and

on receiving the command, storing the aging time as a block time stamp.

11. A control circuit for determining a dwell time in a memory circuit after a shutdown of the memory circuit, comprising:

a memory interface configured to be operably coupled to the memory circuit; and

a controller, wherein the controller is configured to:

store a first test block before the shutdown;

save a second test block after the memory circuit is powered on;

perform a first read level sweep of the first test block to determine a first read level voltage with minimum errors, including determining the first read level voltage as a function of a nominal read level voltage and a first estimation parameter;

perform a second read level sweep of the second test block to determine a second read level voltage with minimum errors, including determining the second read level voltage as a function of the nominal read level voltage and a second estimation parameter;

calculate a shutdown threshold voltage (V T ) shift as a function of the first read level voltage and the second read level voltage; and

calculate a shutdown duration as a function of the shutdown V T shift.

12. The control circuit of claim 11 , wherein the controller is further configured to:

read a drive temperature after the drive temperature has stabilized;

calculate a revised duration as a function of the shutdown duration and the drive temperature and a reference temperature; and

calculate the dwell time as a function of a current time and a block time stamp and the revised duration.

13. The control circuit of claim 12 , wherein the controller being configured to calculate the revised duration as a function of the shutdown duration and the drive temperature and the reference temperature includes the controller being configured to:

calculate a temperature acceleration factor as a function of the drive temperature and the reference temperature; and

calculate the revised duration as a function of the shutdown duration and the temperature acceleration factor.

14. The control circuit of claim 12 , wherein the controller is further configured to:

store a pre-shutdown temperature before the shutdown, wherein the controller being configured to calculate the dwell time as a function of the current time and the block time stamp and the revised duration includes the controller being configured to:

retrieve the pre-shutdown temperature and the block time stamp after the memory circuit is powered on,

calculate a temperature acceleration factor as a function of the drive temperature and the pre-shutdown temperature, and

calculate the dwell time as a function of the current time, the block time stamp, the revised duration, and the temperature acceleration factor.

15. The control circuit of claim 14 , wherein the controller being configured to calculate the dwell time includes the controller being configured to:

calculate a temporary duration by subtracting the block time stamp from the current time; and

multiply the temporary duration by the temperature acceleration factor and then add the revised duration.

16. The control circuit of claim 11 , wherein the controller being configured to calculate a shutdown duration as a function of the shutdown V T shift includes the controller being configured to index a lookup table by the shutdown V T shift and a program/erase cycle to retrieve the shutdown duration.

17. The control circuit of claim 11 , wherein the controller is further configured to:

calculate the dwell time as a function of a current time and a first block time stamp associated with a memory block and a temperature acceleration factor;

calculate an updated block time stamp by subtracting the dwell time from a current time; and

store the updated block time stamp.

18. The control circuit of claim 11 , wherein the controller being configured to store the first test block includes the controller being configured to:

write data to a memory block; and

store an address of the memory block.

19. The control circuit of claim 11 , wherein the controller is further configured to:

calculate a temperature acceleration factor as a function of a drive temperature;

calculate a current aging time as a function of a current time value and the temperature acceleration factor;

calculate an post-shutdown aging time as a function of the current aging time and the shutdown duration;

read a block time stamp; and

calculate the dwell time by subtracting the block time stamp from the post-shutdown aging time.

20. The control circuit of claim 11 , wherein the controller is further configured to:

calculate a temperature acceleration factor as a function of a drive temperature;

calculate a current aging time as a function of a current time value and the temperature acceleration factor;

receive a command representative of a write operation; and

on receiving the command, store the aging time as a block time stamp.

21. A system for determining a dwell time in a memory circuit after a shutdown of the memory circuit, comprising:

a host interface configured to be operably coupled to a host device, to receive data from the host device, and to send data to the host device;

a temperature sensor;

a storage medium interface operably coupled to a volatile memory;

a memory interface operably coupled to the memory circuit; and

a controller operably coupled to the host interface, wherein the controller is operable to:

store a first test block on the memory circuit before the shutdown;

store a second test block on the memory circuit after the memory circuit is powered on;

perform a first read level sweep of the first test block to determine a first read level voltage with minimum errors, including determining the first read level voltage as a function of a nominal read level voltage and a first estimation parameter;

perform a second read level sweep of the second test block to determine a second read level voltage with minimum errors, including determining the second read level voltage as a function of the nominal read level voltage and a second estimation parameter;

calculate a shutdown V T shift as a function of the first read level voltage and the second read level voltage; and

calculate a shutdown duration as a function of the shutdown V T shift.

22. The system of claim 21 , wherein the controller is further configured to:

store a pre-shutdown temperature received from the temperature sensor before the shutdown;

read from the temperature sensor a drive temperature after the memory circuit is powered on and after the drive temperature has stabilized;

calculate a revised duration as a function of the shutdown duration and the drive temperature and a reference temperature; and

calculate the dwell time as a function of a current time and a block time stamp and the revised duration.

23. The system of claim 21 , wherein the controller is further configured to:

calculate a temperature acceleration factor as a function of a drive temperature;

calculate a current aging time as a function of a current time value and the temperature acceleration factor;

calculate an post-shutdown aging time as a function of the current aging time and the shutdown duration;

read a block time stamp; and

calculate the dwell time by subtracting the block time stamp from the post-shutdown aging time.

Assignments (12)