1. A method of writing data in a phase change memory cell in a memory, the memory comprising a plurality of phase change memory cells, and the method comprising: 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.