| 摘要 |
PURPOSE: An optimized threshold search in analog memory cells is provided to evaluate readout performance multiple sets of read thresholds while actually reading the memory cells using only a small subset of these sets. CONSTITUTION: A method for setting thresholds for reading analog memory cells comprises: storing data in a group of analog memory cells; reading the memory cells in the group using first read thresholds, to produce first readout results (70); re-reading the memory cells in the group using second read thresholds, to produce second readout results (74); defining third read thresholds, which comprise at least one of the first read thresholds and at least one of the second read thresholds; evaluating readout performance of the first, second and third read thresholds based on the first and second readout results; and selecting the first, second or third read thresholds based on the evaluated readout performance, and performing data recovery using the selected read thresholds. [Reference numerals] (70) Read the memory cells in the group using first read thresholds; (74) Re-read the memory cells in the group using second read thresholds; (78) Read the memory cells in the group using sub thresholds; (82) Compose the read result of hybrid combination of first and second read thresholds based on the sub thresholds without re-read the memory cells; (86) Select optimal read thresholds
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