| abstract |
The SSD controller dynamically adjusts the read thresholds in the NVM to reduce errors due to device threshold voltage distribution shifts, thereby improving the performance, reliability, and / or cost of the storage sub-system such as the SSD. The retention drift clock uses one or more reference pages (or ECC units or blocks) of one or more NVM's as read thresholds through time / temperature references, A function of these values is used as a measure of drift. At some initial time, one or more reference pages are programmed and an initial read threshold is measured for each of one or more reference pages. In some embodiments, the read thresholds are all reference pages on the same die; And one or more of all reference pages on the same or more die in the I / O device. |