Cell sensing circuit for phase change memory and methods thereof

A method for sensing a phase change memory, comprising:

• providing a sensing circuit having a sense amplifier, and two identical stable currents respectively received by a reference cell and a target cell of the phase change memory;
• establishing a cell voltage of the target cell and a reference voltage of the reference cell respectively via the two identical stable currents;
• and
• using the sense amplifier to determine a logic state of the target cell based on a voltage difference between the reference voltage and the cell voltage.

A method for sensing a phase change memory having a multi-level cell with plural cells, comprising:

• providing plural reference states;
• setting up all the plural cells as unmarked;
• and
• sensing and comparing the unmarked plural cells with a specific one of the plural reference states from a lowest value of the plural reference states to a highest value of the plural reference states to obtain plural cell signals to determine respective logic states of the plural cells.