US Patent 7787281 Writing circuit for a phase change memory

A phase change memory writing circuit is provided. The circuit comprises a writing path and a fast write control unit. The writing path further comprises a current driving unit, a first switch device and a phase change memory cell. The current driving unit is coupled to a high voltage source and outputs a driving current. The first switch device is controlled by a first control signal. The fast write control unit is coupled to the writing path to provide a writing voltage to the writing path. When the first switch device is turned off, the fast write control unit outputs the writing voltage to the writing path. When the first switch device is turned on, the fast write control unit stops outputting the writing voltage to the writing path.