Reading soft bits simultaneously

摘要

Methods and devices for simultaneously verifying or reading multiple states in non-volatile storage are disclosed. Methods and devices for efficiently reducing or eliminating cross-coupling effects in non-volatile storage are disclosed. Methods and devices for efficiently performing reads at a number of voltages to search for the threshold voltage of a memory cell are disclosed. Memory cells on different NAND strings that are read at the same time may be tested for different threshold voltage levels. Memory cells may be tested for different threshold voltages by applying different gate-to-source voltages to memory cells being tested for different threshold voltages. Memory cells may be tested for different threshold voltages by applying different drain to source voltages to the memory cells. Different amounts of compensation for cross-coupling affects may be applied to memory cells on different NAND strings that are read or programmed at the same time. A binary search may be performed.

主权项

1. A method for operating non-volatile storage that includes a plurality of NAND strings of non-volatile storage elements that are programmed to “n+1” data states, the method comprising:
performing “n” sense operations at “n” reference voltages to determine whether the threshold voltage of each non-volatile storage element in a subset of the non-volatile storage elements is greater or less than each of the “n” reference voltages; and performing an additional sense operation for each of the “n” sense operations, each of the additional sense operations includes simultaneously sensing a first group of non-volatile storage elements in the subset that have a threshold voltage greater than the “nth” reference voltage at a first offset voltage from the “nth” reference voltage while sensing a second group of non-volatile storage elements in the subset that have a threshold voltage less than the “nth” reference voltage at a second offset voltage from the “nth” reference voltage.