Patent ID: 9177660
Filing Date: 2015-11-03
Classification: G06F,G11C

Abstract:
1. A method of operating a memory device having a plurality of memory cells, the method comprising: changing a first read voltage, for determining whether data stored in memory cells is a first voltage state or a second voltage state, to a voltage within a first range and determining the voltage within the first range as a first select read voltage; and changing a second read voltage, for determining whether the data stored in the plurality of memory cells is a third voltage state or a fourth voltage state, to a voltage within a second range which is different from the first range and determining the voltage within the second range as a second select read voltage, wherein the first and second voltage states are different from the third and fourth voltage states, the first voltage state and the second voltage overlap each other, the third voltage state and the fourth voltage state overlap each other, and a difference between a voltage at an intersection of the third and fourth voltage states and the second read voltage is greater than a difference between a voltage at an intersection of the first and second voltage states and the first read voltage.