Device controlling phase change storage element and method thereof

1. 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.

2. The device as claimed in claim 1 , wherein the conduction period controller further comprises:

an oscillator, comprising a plurality of inverters that are coupled in series to generate an oscillating signal;

a counter, counting the oscillations of the oscillating signal and setting the conduction period inversely proportional to the counting result; and

a driving current generator, generating a driving current for the inverters and making the driving current inversely proportional to the reference resistor or the reference phase change storage element to which the first switch is coupled.

3. The device as claimed in claim 2 , wherein the driving current generator comprises:

a transistor, generating the driving current, and coupled in series with the reference resistor or the reference phase change storage element to which the first switch is coupled; and

a bias source, coupled to the gate of the transistor.

4. The device as claimed in claim 2 , wherein the driving current generator comprises:

a voltage division resistor, coupled in series with the reference resistor or the reference phase change storage element to which the first switch is coupled to generate a divided voltage;

a bias source, providing a voltage drop for the voltage division resistor and the reference resistor or the reference phase change storage element to which the first switch is coupled; and

a transistor, generating the write current, and having a gate controlled by the divided voltage.

5. A device controlling a phase change storage element, comprising:

a current source, providing a write current to be conducted to a reference phase change element in a first mode and to be conducted to the phase change storage element in a second mode;

the 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; and

a conduction period controller, coupled 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 conduction period controller is coupled;

wherein:

in the first operation mode, the reference resistor is coupled to the conduction period controller and the write current is forced 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 conduction period controller and the write current is forced into the phase change storage element.

6. The device as claimed in claim 5 , wherein the conduction period controller further comprises:

an oscillator, comprising a plurality of inverters that are coupled in series to generate an oscillating signal;

a counter, counting the oscillations of the oscillating signal and setting the conduction period inversely proportional to the counting result; and

a driving current generator, generating a driving current for the inverters and making the driving current inversely proportional to the reference resistor or the reference phase change storage element to which the conduction period controller is coupled.

7. The device as claimed in claim 6 , wherein the driving current generator comprises:

a transistor, generating the driving current, and coupled in series with the reference resistor or the reference phase change storage element to which the conduction period controller is coupled; and

a bias source, coupled to the gate of the transistor.

8. The device as claimed in claim 6 , wherein the driving current generator comprises:

a voltage division resistor, coupled in series with the reference resistor or the reference phase change storage element to which the conduction period controller is coupled to generate a divided voltage;

a bias source, providing a voltage drop for the voltage division resistor and the reference resistor or the reference phase change storage element to which the conduction period controller is coupled; and

a transistor, generating the write current, and having a gate controlled by the divided voltage.