Data storage device and method for inferring a read threshold using a time tag determination
A data storage device has an inference engine that can infer a read threshold based on a non-linear function of inputs that reflect current memory and data conditions. The read threshold can be used in reading a wordline in the memory. Using a machine-learning-based approach to infer a read threshold can provide significant improvement in read threshold accuracy, which can reduce bit error rate and also improve latency, throughput, power consumption, and quality of service.
1. In a data storage device comprising a memory, a method comprising:
using firmware in the data storage device to infer a read threshold to use in reading a wordline in the memory, wherein the read threshold is inferred:
prior to the data storage device receiving a read command from a host that causes the wordline to be read;
only during a time and temperature update; and
based only on one or more inputs available during the time and temperature update, wherein a wordline number of the wordline is not one of the one or more inputs; and
in response to receiving the read command from the host:
looking up the wordline number in a pre-calibrated wordline zoning table comprising a plurality of predefined correction values associated with a respective plurality of wordline numbers;
modifying the inferred read threshold based on a correction value associated with the wordline number in the pre-calibrated wordline zoning table; and
using the modified inferred read threshold to read the wordline.
2. The method of claim 1 , wherein the read threshold is inferred by using machine learning in a background and a static table in a foreground.
3. The method of claim 2 , wherein the machine learning is trained to take into account future static tables in the foreground.
4. The method of claim 1 , wherein the one or more inputs comprises programming temperature.
5. The method of claim 1 , wherein the one or more inputs comprises elapsed time since a prior time tag and temperature update.
6. The method of claim 1 , wherein the one or more inputs comprises bit error rate (BER) information.
7. The method of claim 1 , further comprising updating the read threshold periodically.
8. A data storage device comprising:
a memory; and
a processor configured to execute firmware to:
infer a read threshold to use to read a wordline in the memory, wherein the read threshold is inferred:
prior to the data storage device receiving a read command from a host that causes the wordline to be read;
only during a time and temperature update; and
based only on one or more inputs available during the time and temperature update, wherein a wordline number of the wordline is not one of the one or more inputs; and
in response to receiving the read command from the host:
look up the wordline number in a pre-calibrated wordline zoning table comprising a plurality of predefined correction values associated with a respective plurality of wordline numbers;
modify the inferred read threshold based on a correction value associated with the wordline number in the pre-calibrated wordline zoning table; and
use the modified inferred read threshold to read the wordline.
9. The data storage device of claim 8 , wherein the one or more inputs comprise programming temperature.
10. The data storage device of claim 8 , wherein the one or more inputs comprise elapsed time since a prior time tag and temperature update.
11. The data storage device of claim 8 , wherein the one or more inputs comprise bit error rate (BER) information.
12. The data storage device of claim 8 , wherein the processor is further configured to periodically infer read thresholds.
13. The data storage device of claim 12 , wherein the read thresholds are inferred when a time tag threshold has changed.
14. The data storage device of claim 12 , wherein the read thresholds are inferred when a temperature has changed.
15. The data storage device of claim 8 , wherein the memory comprises a three-dimensional memory.
16. A data storage device comprising:
a memory; and
means for:
using firmware in the data storage device to infer a read threshold to use in reading a wordline in the memory, wherein the read threshold is inferred:
prior to the data storage device receiving a read command from a host that causes the wordline to be read;
only during a time and temperature update; and
based only on one or more inputs available during the time and temperature update, wherein a wordline number of the wordline is not one of the one or more inputs; and
in response to receiving the read command from the host:
looking up the wordline number in a pre-calibrated wordline zoning table comprising a plurality of predefined correction values associated with a respective plurality of wordline numbers;
modifying the inferred read threshold based on a correction value associated with the wordline number in the pre-calibrated wordline zoning table; and
using the modified inferred read threshold to read the wordline.
17. The data storage device of claim 12 , wherein the read thresholds are inferred when a program-erase-cycle (PEC) count has changed.