Patent ID: 8159881
Filing Date: 2012-04-17
Classification: G11C,H01L

Abstract:
1. A system comprising: a voltage generator configured to generate K voltages to be applied to memory cells, wherein the K voltages are used to determine a reference voltage used to read the memory cells, where K is an integer greater than 1; a reference voltage setting module configured to selectively set the reference voltage to a value between two adjacent ones of the K voltages or one of the two adjacent ones of the K voltages; a sensing module configured to sense currents through the memory cells when each of the K voltages is applied to the memory cells; and a counting module configured to count, based on the currents, numbers of the memory cells having threshold voltages between pairs of the K voltages, wherein the pairs include adjacent ones of the K voltages, wherein the reference voltage setting module selects one of the pairs having a smallest of the numbers and sets the reference voltage to the value between or equal to one of the two adjacent ones of the K voltages corresponding to the one of the pairs.