Patent ID: 9330775
Filing Date: 2016-05-03
CPC Classification: G11C

Claim Text:
1. A method of operating a flash memory, the method comprising: counting the number of memory cells having threshold voltages included in a first adjacent threshold voltage range defined by a first reference read voltage for discriminating between a first pair of threshold voltage distributions adjacently located and a first search read voltage having a first voltage difference with the first reference read voltage; counting the number of memory cells having threshold voltages included in a second adjacent threshold voltage range defined by the first reference read voltage and a second search read voltage having a second voltage difference with the first reference read voltage; and setting a first optimal read voltage based on a count difference between the counted number of the memory cells having the threshold voltages included in the first adjacent threshold voltage range and the counted number of the memory cells having the threshold voltages included in the second adjacent threshold voltage range.