Compensation loop for read voltage adaptation
View Patent ↗The disclosure is directed to a system and method for nominal read voltage variations of a flash device. N reads are performed, each at a selected voltage offset from an initial read voltage. An N bit digital pattern associated with the selected voltage offsets is generated for the N reads. The N bit digital pattern generated by the N reads is mapped to a signed representation. A voltage adjustment based upon the signed representation is applied to at least partially compensate for a variation of the nominal read voltage to reduce bit error rate of the flash device.
1. A system for compensating nominal voltage variations of a flash device, comprising:
a flash device configured to execute N reads, each of the N reads having a selected voltage offset from an initial nominal read voltage, the N reads generating an N bit digital pattern associated with the selected voltage offsets;
a mapping module configured to receive the N bit digital pattern generated by the N reads, the mapping module further configured to map the N bit digital pattern to a signed representation; and
a voltage compensator configured to provide a voltage adjustment based upon the signed representation to at least partially compensate for a variation of the nominal read voltage.
2. The system of claim 1 , wherein the flash device includes a flash analog-to-digital converter configured to generate the N bit digital pattern associated with the N reads.
3. The system of claim 1 , wherein the system is configured to compensate for nominal voltage variations after a selected number of memory cycles occur or after a read failure occurs.
4. The system of claim 1 , further comprising:
an adaptation loop configured to receive the signed representation from the mapping module, the adaptation loop further configured to adaptively provide one or more numerical adjustments based upon the magnitude and sign of the signed representation, wherein the voltage adjustment is determined utilizing the one or more numerical adjustments from the adaptation loop.
5. A system for compensating nominal voltage variations of a flash device, comprising:
a flash device configured to execute N reads, each of the N reads having a selected voltage offset from an initial nominal read voltage, the N reads generating an N bit digital pattern associated with the selected voltage offsets;
a mapping module configured to receive the N bit digital pattern generated by the N reads, the mapping module further configured to map the N bit digital pattern to a signed representation;
an adaptation loop configured to receive the signed representation from the mapping module, the adaptation loop further configured to adaptively provide one or more numerical adjustments based upon the magnitude and sign of the signed representation;
a voltage compensator configured to provide a voltage adjustment based upon the one or more numerical adjustments from the adaptation loop to at least partially compensate for a variation of the nominal read voltage; and
a calculation module configured to determine a log-likelihood ratio based upon an adjusted nominal read voltage.
6. The system of claim 5 , wherein the log-likelihood ratio (LLR) is determined in accordance with the following equation:
LLR= K ( y )* y,
where y is the adjusted read voltage, and K(y) is a constant based upon y.
7. The system of claim 6 , wherein
K(y)=Kp when y is not less than zero, and
K(y)=Kn when y is less than zero,
where Kp and Kn are selected constants.
8. The system of claim 7 , wherein Kp and Kn are determined utilizing a distribution of values for y.
9. The system of claim 5 , wherein the system is configured to compensate for nominal voltage variations after a read failure occurs.
10. The system of claim 5 , wherein the flash device includes a flash analog-to-digital converter configured to generate the N bit digital pattern associated with the N reads.
11. The system of claim 5 , wherein the signed representation includes a three bit signed binary representation.
12. The system of claim 5 , wherein the system includes at least a portion of a read-retry pathway.
13. A method of compensating nominal voltage variations of a flash device, comprising:
executing N reads, each of the N reads having a selected voltage offset from an initial nominal read voltage;
generating an N bit digital pattern associated with the selected voltage offsets;
mapping the N bit digital pattern to a signed representation; and
providing a voltage adjustment based upon the signed representation to at least partially compensate for a variation of the nominal read voltage.
14. The method of claim 13 , further comprising:
adaptively providing one or more numerical adjustments based upon the magnitude and sign of the signed representation, wherein the voltage adjustment is determined utilizing the one or more numerical adjustments.
15. The method of claim 13 , further comprising:
detecting at least one of a selected number of memory cycles or a read failure.
16. The method of claim 13 , wherein the N bit digital pattern is an output from a flash analog-to-digital converter.
17. The method of claim 13 , further comprising:
determining a log-likelihood ratio based upon an adjusted nominal read voltage.
18. The method of claim 17 , wherein the log-likelihood ratio (LLR) is determined in accordance with the following equation:
LLR= K ( y )* y,
where y is the adjusted read voltage, and K(y) is a constant based upon y.
19. The method of claim 18 , wherein
K(y)=Kp when y is not less than zero, and
K(y)=Kn when y is less than zero,
where Kp and Kn are selected constants.
20. The method of claim 19 , wherein Kp and Kn are determined utilizing a distribution of values for y.