Flash channel parameter management with read scrub
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.
1. An apparatus comprising:
a memory configured to store data; and
a controller configured to
process a plurality of input/output requests to read/write to/from the memory,
generate a plurality of statistics of a plurality of units in a region of the memory as part of a read scrub of the region, wherein the statistics comprise at least one of a total number of bits having a first logical value before a correction made during the read scrub, a total number of bits having the first logical value after the correction, or a total number of bits changed from a second logical value to the first logical value by the correction,
track a plurality of channel parameters that characterize the region based on the plurality of statistics, wherein the plurality of channel parameters comprise a plurality of mean threshold voltages of the units in the region and a plurality of standard deviations from the mean threshold voltages, and
when one or more of the statistics exceeds a corresponding threshold,
separate one or more outlier units from the plurality of units in the region,
separate one or more outlier statistics from the plurality of statistics of the region,
track a plurality of outlier channel parameters that characterize the one or more outlier units based on the one or more outlier statistics, wherein the plurality of outlier channel parameters comprise the mean threshold voltages and the standard deviations from the mean threshold voltages of the one or more outlier units, and the plurality of outlier channel parameters are tracked separately from the tracking of the plurality of channel parameters that characterize the region, and
control one or more reference voltages in the memory based on the plurality of outlier channel parameters when reading the data a plurality of times from the one or more outlier units and based on the plurality of channel parameters that characterize the region when reading the data a plurality of times from the units of the region other than the one or more outlier units.
2. The apparatus according to claim 1 , wherein the region spans a plurality of die that form the memory, and each of the plurality of units in the region comprises a block having a plurality of memory cells.
3. The apparatus according to claim 2 , wherein one or more of the blocks in the region are designated to store redundancy information configured to recover from a failure of one or more of the blocks in the region.
4. The apparatus according to claim 1 , wherein the controller is further configured to separate the one or more outlier statistics of the one or more outlier units from the plurality of statistics of the region while tracking the plurality of channel parameters that characterize the region.
5. The apparatus according to claim 1 , wherein the corresponding threshold comprises a threshold voltage displacement relative to the mean threshold voltages in the region.
6. The apparatus according to claim 1 , wherein the corresponding threshold comprises a threshold voltage spread relative to the standard deviations in the region.
7. The apparatus according to claim 1 , wherein the corresponding threshold comprises a read error rate threshold.
8. The apparatus according to claim 1 , wherein the corresponding threshold comprises a read disturb count threshold.
9. The apparatus according to claim 1 , wherein the memory and the controller are part of a solid-state drive.
10. A method for channel parameter management with read scrub, comprising the steps of:
generating a plurality of statistics of a plurality of units in a region of a memory as part of the read scrub of the region, wherein the statistics comprise at least one of a total number of bits having a first logical value before a correction made during the read scrub, a total number of bits having the first logical value after the correction, or a total number of bits changed from a second logical value to the first logical value by the correction;
tracking a plurality of channel parameters that characterize the region based on the plurality of statistics, wherein the plurality of channel parameters comprise a plurality of mean threshold voltages of the units in the region and a plurality of standard deviations from the mean threshold voltages; and
when one or more of the statistics exceeds a corresponding threshold,
separating one or more outlier units from the plurality of units in the region,
separating one or more outlier statistics from the plurality of statistics of the region,
tracking a plurality of outlier channel parameters that characterize the one or more outlier units based on the one or more outlier statistics, wherein the plurality of outlier channel parameters comprise the mean threshold voltages and the standard deviations from the mean threshold voltages of the one or more outlier units, and the plurality of outlier channel parameters are tracked separately from the tracking of the plurality of channel parameters that characterize the region, and
controlling with a circuit one or more reference voltages in the memory based on the plurality of outlier channel parameters when reading data a plurality of times from the one or more outlier units and based on the plurality of channel parameters that characterize the region when reading the data a plurality of times from the units of the region other than the one or more outlier units.
11. The method according to claim 10 , wherein the region spans a plurality of die that form the memory, and each of the plurality of units in the region comprises a block having a plurality of memory cells.
12. The method according to claim 11 , wherein one or more of the blocks in the region are designated to store redundancy information configured to recover from a failure of one or more of the blocks in the region.
13. The method according to claim 10 , further comprising the step of:
separating the one or more outlier statistics of the one or more outlier units from the plurality of statistics of the region while tracking the plurality of channel parameters that characterize the region.
14. The method according to claim 10 , wherein the corresponding threshold comprises a threshold voltage displacement relative to the mean threshold voltages in the region.
15. The method according to claim 10 , wherein the corresponding threshold comprises a threshold voltage spread relative to the standard deviations in the region.
16. The method according to claim 10 , wherein the corresponding threshold comprises a read error rate threshold.
17. The method according to claim 10 , wherein the corresponding threshold comprises a read disturb count threshold.
18. The method according to claim 10 , wherein the steps are performed in a solid-state drive.
19. An apparatus comprising:
an interface configured to process a plurality of read/write operations to/from a memory; and
a control circuit configured to
generate a plurality of statistics of a plurality of units in a region of the memory as part of a read scrub of the region, wherein the statistics comprise at least one of a total number of bits having a first logical value before a correction made during the read scrub, a total number of bits having the first logical value after the correction, or a total number of bits changed from a second logical value to the first logical value by the correction,
track a plurality of channel parameters that characterize the region based on the plurality of statistics, wherein the plurality of channel parameters comprise a plurality of mean threshold voltages of the units in the region and a plurality of standard deviations from the mean threshold voltages, and
when one or more of the statistics exceeds a corresponding threshold,
separate one or more outlier units from the plurality of units in the region,
separate one or more outlier statistics from the plurality of statistics of the region,
track a plurality of outlier channel parameters that characterize the one or more outlier units based on the one or more outlier statistics, wherein the plurality of outlier channel parameters comprise the mean threshold voltages and the standard deviations from the mean threshold voltages of the one or more outlier units, and the outlier channel parameters are tracked separately from the tracking of the plurality of channel parameters that characterize the region, and
control one or more reference voltages in the memory based on the plurality of outlier channel parameters when reading data a plurality of times from the one or more outlier units and based on the plurality of channel parameters that characterize the region when reading the data a plurality of times from the units of the region other than the one or more outlier units.
20. The apparatus according to claim 19 , wherein the interface and the control circuit are part of a solid-state drive controller.