FLASH CHANNEL PARAMETER MANAGEMENT WITH READ SCRUB

• US 20140095110A1
• Filed: 10/01/2012
• Published: 04/03/2014
• Est. Priority Date: 10/01/2012
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: LSI Corporation (Broadcom, Inc.)
• Inventors: Chen, Zhengang, Haratsch, Erich F.
• Granted Patent: US 9,847,139 B2
• Time in Patent Office: Days
• US Class Current: 702/179
• CPC Class Codes: G11C 16/00 Erasable programmable read-only memories G11C14/00 takes precedence
• CPC Class Codes: G11C 2029/0409 Online test
• CPC Class Codes: G11C 29/021 in voltage or current generators
• CPC Class Codes: G11C 29/028 with adaption or trimming of parameters

Abstract

An apparatus having a first circuit and a second circuit is disclosed. The first circuit may be configured to generate statistics of a region of a memory circuit as part of a read scrub of the region. The region may have multiple units of data. The memory circuit may be configured to store the data in a nonvolatile condition. The second circuit is generally configured to (i) track one or more parameters of the region based on the statistics, (ii) determine when one or more of the statistics of one or more outliers of the units in the region exceeds a corresponding threshold and (iii) track the parameters of the outlier units separately from the parameters of the region in response to exceeding the corresponding threshold. The parameters generally control one or more reference voltages used to read the data from the region.

Claims

1. An apparatus comprising:

a first circuit configured to generate a plurality of statistics of a region of a memory circuit as part of a read scrub of said region, wherein (i) said region comprises a plurality of units of data and (ii) said memory circuit is configured to store said data in a nonvolatile condition; and

a second circuit configured to (i) track one or more parameters of said region based on said statistics, (ii) determine when one or more of said statistics of one or more outliers of said units in said region exceeds a corresponding threshold and (iii) track said parameters of said outlier units separately from said parameters of said region in response to exceeding said corresponding threshold, wherein said parameters control one or more reference voltages used to read said data from said region.

2. The apparatus according to claim 1, wherein (i) said memory circuit comprises a flash memory, (ii) said memory circuit is configured to store said data by adjusting a plurality of respective charge states in a plurality of memory cells, (iii) each of said respective charge states corresponds to one of a plurality of threshold voltages and (iv) said parameters of said region track (a) a drift of a plurality of mean voltages among said threshold voltages in said region and (b) a respective spread of said threshold voltages about said mean voltages in said region.

3. The apparatus according to claim 1, wherein (i) said region spans a plurality of die that form said memory circuit and (ii) each of said units comprises a block of memory cells.

4. The apparatus according to claim 3, wherein one or more of said blocks in said region store redundancy information configured to recover from a failure of one or more of said blocks in said region.

5. The apparatus according to claim 1, wherein said second circuit is further configured to remove said statistics of said outlier units from said statistics of said region.

6. The apparatus according to claim 1, wherein said corresponding threshold comprises a displacement of a first mean voltage of a plurality of threshold voltages in said outlier units relative to a second mean voltage of said threshold voltages in said region.

7. The apparatus according to claim 1, wherein said corresponding threshold comprises a spread of a plurality of threshold voltages in said outlier units.

8. The apparatus according to claim 1, wherein said corresponding threshold comprises an error rate in reading from said outlier units.

9. The apparatus according to claim 1, wherein said corresponding threshold comprises an read disturb count in said outlier units.

10. The apparatus according to claim 1, wherein said apparatus is implemented as one or more integrated circuits.

11. A method for channel parameter management with read scrub, comprising the steps of:

(A) generating a plurality of statistics of a region of a memory circuit as part of said read scrub of said region, wherein (i) said region comprises a plurality of units of data and (ii) said memory circuit is configured to store said data in a nonvolatile condition;

(B) tracking one or more parameters of said region based on said statistics, wherein said parameters control one or more reference voltages used to read said data from said region;

(C) determining when one or more of said statistics of one or more outliers of said units in said region exceeds a corresponding threshold; and

(D) tracking said parameters of said outlier units separately from said parameters of said region in response to exceeding said corresponding threshold.

12. The method according to claim 11, wherein (i) said memory circuit comprises a flash memory, (ii) said memory circuit is configured to store said data by adjusting a plurality of respective charge states in a plurality of memory cells, (iii) each of said respective charge states corresponds to one of a plurality of threshold voltages and (iv) said parameters of said region track (a) a drift of a plurality of mean voltages among said threshold voltages in said region and (b) a respective spread of said threshold voltages about said mean voltages in said region.

13. The method according to claim 11, wherein (i) said region spans a plurality of die that form said memory circuit and (ii) each of said units comprises a block of memory cells.

14. The method according to claim 13, wherein one or more of said blocks in said region store redundancy information configured to recover from a failure of one or more of said blocks in said region.

15. The method according to claim 11, further comprising the step of:

removing said statistics of said outlier units from said statistics of said region.

16. The method according to claim 11, wherein said corresponding threshold comprises a displacement of a first mean voltage of a plurality of threshold voltages in said outlier units relative to a second mean voltage of said threshold voltages in said region.

17. The method according to claim 11, wherein said corresponding threshold comprises a spread of a plurality of threshold voltages in said outlier units.

18. The method according to claim 11, wherein said corresponding threshold comprises an error rate in reading from said outlier units.

19. The method according to claim 11, wherein said corresponding threshold comprises an read disturb count in said outlier units.

20. An apparatus comprising:

means for generating a plurality of statistics of a region of a memory circuit as part of a read scrub of said region, wherein (i) said region comprises a plurality of units of data and (ii) said memory circuit is configured to store said data in a nonvolatile condition;

means for tracking one or more parameters of said region based on said statistics, wherein said parameters control one or more reference voltages used to read said data from said region;

means for determining when one or more of said statistics of one or more outliers of said units in said region exceeds a corresponding threshold; and

means for tracking said parameters of said outlier units separately from said parameters of said region in response to exceeding said corresponding threshold.