A method of writing data in a phase change memory includes receiving write data to be written to a selected phase change memory cell in the plurality of phase change memory cells, sensing data stored in the selected phase change memory cell, determining whether or not the sensed data is equal to the write data, and if the sensed data is not equal to the write data, iteratively applying a write current to the selected phase change memory cell, wherein a resistance state of the phase change memory cell is changed by heat corresponding to a level of the write current, and the level of the write current is changed between successive iterative applications.