Patent ID: 8125827
Filing Date: 2012-02-28
Classification: G06F,G11C

Abstract:
1. A method of operating a nonvolatile memory device, the method comprising: storing reference data in a plurality of memory cells; reading the plurality of memory cells using a first read voltage; determining a first number of cells meeting a predetermined criterion in response to the reading of the plurality of memory cells using the first read voltage; reading the plurality of memory cells using a second read voltage differing from the first read voltage by a predetermined voltage difference; determining a second number of cells meeting the predetermined criterion responsive to the reading of the plurality of memory cells using the second read voltage; determining a maximum value of a threshold voltage distribution of the plurality of memory cells responsive to a comparison of the first number of cells and the second number of cells; and modifying a read voltage of the nonvolatile memory device based on the determined maximum value of the threshold voltage distribution.