Patent ID: 7796455

Claim:
A device controlling a phase change storage element, comprising: a current source, providing a write current; a reference phase change storage element, produced next to the phase change storage element; a reference resistor, having a resistance equal to an ideal set mode resistance of the reference phase change storage element; a conduction period controller, comprising a first switch for coupling to the reference resistor or the reference phase change storage element, and controlling a conduction period of the write current to be proportional to the reference resistor or the reference phase change storage element to which the first switch is coupled; and a second switch, coupling the write current to the reference phase change storage element or the phase change storage element, wherein the operation of the device comprises a first operation mode and a second operation mode, and wherein: in the first operation mode, the reference resistor is coupled to the first switch and the second switch forces the write current into the reference phase change storage element, and the conduction period controller controls the conduction period equal to an ideal conduction period of the reference phase change storage element; and in the second operation mode, the reference phase change storage element is coupled to the first switch and the second switch forces the write current into the phase change storage element.