Refresh architecture and algorithm for non-volatile memories

1. A method of refreshing a memory array in a non-volatile memory device, the method comprising:

entering a system on state;

performing a first refresh operation in the non-volatile memory device after entering the system-on state;

entering a system-off state after the first refresh operation is performed; and

performing a second refresh operation in the non-volatile memory device after entering the system-off state, wherein the first and second memory refresh operations are performed while the non-volatile memory device is powered by a same power unit.

2. The method of claim 1 , wherein:

performing the first refresh operation includes reading a subset of the memory array; and

performing the second refresh operation includes reading every operational cell in the memory array.

3. The method of claim 1 , wherein performing the first refresh operation includes:

reading a subset of the memory array; and

reprogramming cells in the subset of the memory array, such that the cells store data corrected by an error correction encoding algorithm.

4. The method of claim 3 , wherein performing the second refresh operation includes:

reading cells of the memory array against a reference level; and

reprogramming cells that fail the reference level.

5. The method of claim 1 , wherein the second refresh operation is performed repetitively at a frequency based on a temperature of the non-volatile memory device after entering the system-off state.

6. The method of claim 1 , wherein the second refresh operation is performed in response to an increase in temperature when non-volatile memory device enters the system-off state.

7. A method of refreshing a memory array in a non-volatile memory device, the method comprising:

entering a system on state;

performing a first refresh operation in the non-volatile memory device after entering the system-on state;

entering a system-off state after the first refresh operation is performed; and

performing a second refresh operation in the non-volatile memory device after entering the system-off state, wherein the non-volatile memory device receives power from an automobile battery, and entering the system-on state occurs when an automobile ignition is actuated.

8. A method of refreshing a memory array in a non-volatile memory device, the method comprising:

entering a system on state;

performing a first refresh operation in the non-volatile memory device after entering the system-on state;

entering a system-off state after the first refresh operation is performed; and

performing a second refresh operation in the non-volatile memory device after entering the system-off state, wherein the non-volatile memory device receives power from an automobile battery, and entering the system-off state occurs when an automobile ignition is actuated.

9. A method of refreshing a memory array in a non-volatile memory device, the method comprising:

entering a system on state;

performing a first refresh operation in the non-volatile memory device after entering the system-on state;

entering a system-off state after the first refresh operation is performed; and

performing a second refresh operation in the non-volatile memory device after entering the system-off state, wherein the non-volatile memory device receives power from an automobile battery, and wherein:

entering the system-on state occurs when an automobile ignition is actuated an engine on; and

entering the system-off state occurs when the automobile ignition is actuated to turn the engine off.

10. A non-volatile memory device comprising:

a memory array; and

a refresh controller coupled to the memory array, the refresh controller configured to:

control a first refresh operation performed on the memory array after a system-on state is entered; and

control a second refresh operation performed on the memory array after a system-off state is entered, the system-off state occurring after first refresh operation is performed, wherein the first and second memory refresh operations are performed while the non-volatile memory device is powered by a same power unit.

11. The non-volatile memory device of claim 10 , wherein the refresh controller is configured to initiate one of the first and second refresh operations in response to output from a temperature sensor.

12. The non-volatile memory device of claim 10 , wherein the refresh controller is configured to initiate one of the first and second refresh operations in response to output from a refresh timer.

13. A non-volatile memory device comprising:

a memory array; and

a refresh controller coupled to the memory array, the refresh controller configured to:

control a first refresh operation performed on the memory array after a system-on state is entered; and

control a second refresh operation performed on the memory array after a system-off state is entered, the system-off state occurring after first refresh operation is performed, wherein the non-volatile memory device is configured to receive power from an automobile battery, and the refresh controller is configured to initiate the second refresh operation when an automobile ignition is actuated.

14. The non-volatile memory device of claim 10 , wherein the refresh controller is configured to control:

reading of a subset of the memory array during the first refresh operation; and

reprogramming of cells in the subset of the memory array, such that the cells store data corrected by an error correction encoding algorithm.

15. The non-volatile memory device of claim 14 , wherein the refresh controller is configured to control:

reading of cells of the memory array against a reference level during the second refresh operation; and

reprogramming of cells that fail the reference level during the second refresh operation.

16. A system comprising:

a power supply unit configured to couple to an automobile battery;

a memory controller unit coupled to the power supply unit; and

a non-volatile memory device coupled to the memory controller unit, the non-volatile memory device including a memory array, the non-volatile memory device configured to:

perform a first refresh operation on the memory array after the system enters a system-on state; and

perform a second refresh operation on the memory array after the system enters a system-off state, the system off state occurring after the system on state, wherein the first and second memory refresh operations are performed while the non-volatile memory device is powered by a same power unit.

17. The system of claim 16 , wherein the non-volatile memory device is configured to:

read a subset of the memory array during the first refresh operation; and

read every operational cell in the memory array during the second refresh operation.

18. The system of claim 16 , wherein the non-volatile memory device is configured to:

read a subset of the memory array during the first refresh operation; and

reprogram cells in the subset of the memory array, such that the cells store data corrected by an error correction encoding algorithm.

19. The system of claim 18 , wherein the non-volatile memory device is configured to:

read cells of the memory array against a reference level during the second refresh operation; and

reprogram cells that fail the reference level.

20. A system comprising:

a power supply unit configured to couple to an automobile battery;

a memory controller unit coupled to the power supply unit; and

a non-volatile memory device coupled to the memory controller unit, the non-volatile memory device including a memory array, the non-volatile memory device configured to:

perform a first refresh operation on the memory array after the system enters a system-on state; and

perform a second refresh operation on the memory array after the system enters a system-off state, the system off state occurring after the system on state, wherein the non-volatile memory device is configured to perform the second refresh operation in response to an increase in temperature when automobile ignition is actuated to turn an engine off.