Systems and methods of storing data

• US 9,318,166 B2
• Filed: 12/19/2011
• Issued: 04/19/2016
• Est. Priority Date: 07/22/2011
• Status: Expired due to Fees

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: Sharon, Eran, Alrod, Idan
• Primary Examiner(s): Alphonse, Fritz
• Application Number:
  US13/329,788
• Publication Number:
  US 20130024743A1
• Time in Patent Office: 1,583 Days
• Field of Search: 714/773, 714/755, 714/778, 714/780, 714/763
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1044 with specific ECC/EDC distribution
• CPC Class Codes: G06F 11/1068 in sector programmable memories, e.g. flash disk G06F11/1072 takes precedence
• CPC Class Codes: G06F 11/1072 in multilevel memories
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 11/5642 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 16/10 Programming or data input circuits
• CPC Class Codes: G11C 2211/5641 Multilevel memory having cells with different number of storage levels
• CPC Class Codes: G11C 29/78 using programmable devices
• CPC Class Codes: G11C 7/1006 Data managing, e.g. manipulating data before writing or reading out, data bus switches or control circuits therefor

Abstract

A method of reading data in a data storage device with a controller and a memory includes generating, in the memory, a set of bits corresponding to a particular storage element of the memory. The set of bits indicates a group of threshold voltage intervals. A threshold voltage of the particular storage element corresponds to one of the threshold voltage intervals within the group. At least one threshold voltage interval within the group is separated from another threshold voltage interval within the group by an intervening threshold voltage interval that is not within the group. The method also includes sending the set of bits to the controller. The set of bits includes a first hard bit that corresponds to a value read from the particular storage element and a first soft bit that corresponds to a reliability measure.

Claims

1. A method comprising:

in a data storage device with a controller and a memory, the memory including multiple storage elements, performing;

generating, in the memory, a set of bits corresponding to a particular storage element, wherein the set of bits indicates a group of threshold voltage intervals, wherein a threshold voltage of the particular storage element corresponds to one of the threshold voltage intervals within the group, and wherein at least one threshold voltage interval within the group is separated from another threshold voltage interval within the group by an intervening threshold voltage interval that is not within the group; and

sending the set of bits to the controller, wherein the set of bits includes a first hard bit that corresponds to a value read from the particular storage element and a first soft bit that corresponds to a reliability measure.

2. The method of claim 1, wherein the particular storage element is within a physical page of the memory, wherein the physical page includes a first logical page and a second logical page, and wherein a state of the particular storage element corresponds to multiple hard bits that include the first hard bit corresponding to the first logical page and a second hard bit corresponding to the second logical page.

3. The method of claim 2, wherein the set of bits is generated in response to a request to read the first logical page and wherein the set of bits does not include the second hard bit.

4. The method of claim 1, wherein the controller includes a soft input error correction coding (ECC) decoder and wherein the first hard bit and the first soft bit are provided to the soft input ECC decoder as part of an ECC decode operation of data that is read from the memory.

5. The method of claim 1, wherein the first soft bit indicates whether the threshold voltage is within a center region of any of the threshold voltage intervals of the group of threshold voltage intervals.

6. The method of claim 5, wherein the set of bits is sent to the controller in response to a first request from the controller for first stored data, and further comprising, after sending the set of bits to the controller:

receiving, at the memory, a second request from the controller, the second request for additional information corresponding to the first stored data;

determining, at the memory, a second soft bit corresponding to the particular storage element, wherein the second soft bit indicates whether the threshold voltage is within a second region of any of the voltage intervals of the group of threshold voltage intervals, the second region of each particular voltage interval centered substantially at a midpoint of a cell voltage distribution corresponding to a state and differing from the center region; and

sending the second soft bit value to the controller.

7. The method of claim 1, wherein the memory is configured to provide a same soft bit pattern to indicate reliability during a page-by-page read operation as during a sequential read operation.

8. The method of claim 7, wherein the soft bit pattern is independent of a selected mapping scheme of bits to states.

9. The method of claim 1, wherein the set of bits is descrambled at the memory by applying a descrambler to all hard bits of the set of bits without applying the descrambler to any soft bit of the set of bits.

10. The method of claim 1, wherein the memory includes a flash memory and wherein the particular storage element is a multi-level cell (MLC) of the flash memory.

11. The method of claim 1, wherein generating the set of bits is performed using a single sequence of sensing operations occurring at non-uniform voltage intervals.

12. A data storage device comprising:

a controller; and

a memory including multiple storage elements, wherein the memory is configured to generate a set of bits corresponding to a particular storage element and to send the set of bits to the controller, wherein the set of bits indicates a group of threshold voltage intervals, wherein a threshold voltage of the particular storage element corresponds to one of the threshold voltage intervals within the group, and wherein at least one threshold voltage interval within the group is separated from another threshold voltage interval within the group by an intervening threshold voltage interval that is not within the group,

wherein the set of bits includes a first hard bit that corresponds to a value read from the particular storage element and a first soft bit that corresponds to a reliability measure.

13. The data storage device of claim 12, wherein the particular storage element is within a physical page of the memory, wherein the physical page includes a first logical page and a second logical page, and wherein a state of the particular storage element corresponds to multiple hard bits that include the first hard bit corresponding to the first logical page and a second hard bit corresponding to the second logical page.

14. The data storage device of claim 13, wherein the set of bits is generated in response to a request from the controller to read the first logical page and wherein the set of bits does not include the second hard bit.

15. The data storage device of claim 12, wherein the controller includes a soft input error correction coding (ECC) decoder and wherein the controller is configured to provide the first hard bit and the first soft bit to the soft input ECC decoder as part of an ECC decode operation.

16. The data storage device of claim 12, wherein the first soft bit indicates whether the threshold voltage is within a center region of any of the threshold voltage intervals of the group of threshold voltage intervals.

17. The data storage device of claim 12, wherein the first soft bit indicates whether the threshold voltage is within a center region of a cell voltage distribution of cells being programmed to a state while their final read threshold voltages manifest the cell voltage distribution, and wherein the center region belongs to a threshold voltage interval of the group of voltage intervals.

18. The data storage device of claim 16, wherein the memory is configured to send the first set of bits to the controller in response to a first request from the controller for first stored data, wherein the memory is further configured to determine a second soft bit and to send the second soft bit to the controller in response to receiving a second request from the controller, the second request for additional information corresponding to the first stored data, wherein the second soft bit corresponds to the particular storage element and indicates whether the threshold voltage is within a second region of any of the voltage intervals of the group of threshold voltage intervals, and wherein the second region of each particular voltage interval is centered substantially at a midpoint of the particular voltage interval and differs from the center region.

19. The data storage device of claim 12, wherein the memory is configured to provide a same soft bit pattern to indicate reliability during a page-by-page read operation as during a sequential read operation.

20. The data storage device of claim 19, wherein the soft bit pattern is independent of a selected mapping scheme that maps bits to states of a memory cell.

21. The data storage device of claim 12, wherein the memory includes a descrambler and wherein the memory is configured to apply the descrambler to all hard bits of the set of bits without applying the descrambler to any soft bit of the set of bits.

22. The data storage device of claim 12, wherein the memory includes a flash memory and wherein the particular storage element is a multi-level cell (MLC) of the flash memory.