US Patent 10566061 Calibrating optimal read levels

After a predetermined period of time in a life cycle of a flash memory device, a plurality of reliability values corresponding to a plurality of reads of one or more of the plurality of memory cells are generated; each of the reads using a variation of a predetermined read level voltage. An offset voltage is then identified, offset from the read level voltage. The offset voltage corresponds to a zero crossing point in the range of the reliability values. Once the offset voltage is identified, the read level voltage is set to a calibrated voltage based on the offset voltage.