The read channel of a Flash memory cell degrades after repetitive program anderase (P/E) operations. This degradation is often modeled as a function of thenumber of P/E cycles. In contrast, this paper models the degradation as afunction of the cumulative effect of the charge written and erased from thecell. Based on this modeling approach, this paper dynamically allocates voltageusing lower-voltage write thresholds at the beginning of the device lifetimeand increasing the thresholds as needed to maintain the mutual information ofthe read channel in the face of degradation. The paper introduces the techniquein an idealized setting and then removes ideal assumptions about channelknowledge and available voltage resolution to conclude with a practical schemewith performance close to that of the idealized setting.
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