Patent ID: 7675772
Filing Date: 2010-03-09
Classification: G11C

Abstract:
1. A method for operating a memory device, comprising: programming a number of memory cells to one of a number of different threshold voltage (Vt) levels, each level corresponding to a program state; programming a number of reference cells to a Vt level at least as great as an uppermost Vt level of the number of different Vt levels; performing a read operation on the number of reference cells and determining an amount of the number of reference cells which conduct current upon application of a particular read reference voltage to a row select line to which the number of reference cells are coupled; and determining a number of read reference voltages used to determine a particular program state of the memory cell based on the read operation performed on the reference cell; and adjusting at least two of the number of read reference voltages based on the determined amount of the number of reference cells which conduct current upon application of the particular read reference voltage.