Resistance variable memory apparatus

1. A resistance variable memory apparatus comprising:

a resistance variable element for storing data based on a change in an electric resistance;

an electric pulse application device including a first output terminal and a second output terminal, the electric pulse application device being configured to output an electric pulse between the first output terminal and the second output terminal;

a reference node;

a series current path for electrically connecting the first output terminal to the reference node;

a resistance change current path including the resistance variable element and electrically connecting the reference node to the second output terminal via the resistance variable element;

a parallel current path for electrically connecting the reference node to the second output terminal in parallel with the resistance change current path;

a series resistance setting unit for setting a resistance value of the series current path; and

a parallel resistance setting unit for setting a resistance value of the parallel current path;

wherein the resistance variable element has a characteristic in which the resistance variable element in a low-resistance state switches to a high-resistance state, a resistance value of which is higher than a resistance value of the low-resistance state, when a node potential which is a potential of the reference node based on the second output terminal as a reference is larger in absolute value than a first voltage level, and the resistance variable element in the high-resistance state switches from the high-resistance state to the low-resistance state when the node potential is larger in absolute value than a second voltage level which has a polarity identical to a polarity of the first voltage level and is larger in absolute value than the first voltage level; and

wherein the series resistance setting unit is configured to set a resistance value of the series current path and the parallel resistance setting unit is configured to set a resistance value of the parallel current path such that:

a resistance value of the series current path, a resistance value of the parallel current path, a resistance value of the resistance change current path in a state where the resistance variable element is in the high-resistance state, and a resistance value of the resistance change current path in a state where the resistance variable element is in the low-resistance state,

become resistance values at which the node potential is not smaller in absolute value than the first voltage level when the resistance variable element is in the low-resistance state and the electric pulse application device outputs a first electric pulse;

become resistance values at which the node potential is not smaller in absolute value than the second voltage level when the resistance variable element is in the high-resistance state and the electric pulse application device outputs a second electric pulse;

become resistance values at which the node potential is not larger in absolute value than the second voltage level in a state where the electric pulse application device is outputting the first electric pulse after the resistance variable element has switched to the high-resistance state when the resistance variable element is in the low-resistance state and the electric pulse application device outputs the first electric pulse; and

become resistance values at which the node potential is not larger in absolute value than the first voltage level in a state where the electric pulse application device is outputting the second electric pulse after the resistance variable element has switched to the low-resistance state when the resistance variable element is in the high-resistance state and the electric pulse application device outputs the second electric pulse.

2. The resistance variable memory apparatus according to claim 1 ,

wherein when a resistance value of the series current path which occurs when the resistance variable element is switched from the low-resistance state to the high-resistance state is expressed as Rsl,

a resistance value of the series current path which occurs when the resistance variable element is switched from the high-resistance state to the low-resistance state is expressed as Rsh,

a resistance value of the parallel current path which occurs when the resistance variable element is switched from the low-resistance state to the high-resistance state is expressed as Rpl,

a resistance value of the parallel current path which occurs when the resistance variable element is switched from the high-resistance state to the low-resistance state is expressed as Rph,

a resistance value of the resistance change current path which occurs in a state where the resistance variable element is in the low-resistance state is expressed as Rrl,

a resistance value of the resistance change current path which occurs in a state where the resistance variable element is in the high-resistance state is expressed as Rrh,

an absolute value of a potential of the first output terminal based on the second output terminal as a reference which occurs when the first electric pulse is output is expressed as V 1 ,

an absolute value of a potential of the first output terminal based on the second output terminal as a reference which occurs when the second electric pulse is output is expressed as V 2 ,

an absolute value of the first voltage level is expressed as Vlh, and

an absolute value of the second voltage level is expressed as Vhl, formulae (1) to (4) expressed below are satisfied:

V

⁢

⁢

1

×

Rpl

-

Vlh

×

Rpl

Vlh

+

Vlh

×

Rpl

Rrl

≥

Rsl

(

1

)

V

⁢

⁢

1

×

Rpl

-

Vhl

×

Rpl

Vhl

+

Vhl

×

Rpl

Rrh

<

Rsl

(

2

)

V

⁢

⁢

2

×

Rph

-

Vhl

×

Rph

Vhl

+

Vhl

×

Rph

Rrh

≥

Rsh

(

3

)

V

⁢

⁢

2

×

Rph

-

Vlh

×

Rph

Vlh

+

Vlh

×

Rph

Rrl

<

Rsh

.

(

4

)

3. The resistance variable memory apparatus according to claim 1 , wherein the series resistance setting unit is configured to selectively turn on switches of a plurality of current paths which are provided on the series current path in parallel with each other, to set the resistance value of the series current path, the plurality of current paths each including a fixed resistance element and a switch; and

the parallel resistance setting unit is configured to selectively turn on switches of a plurality of current paths which are provided on the series current path in parallel with each other, to set the resistance value of the parallel current path, the plurality of current paths each including a fixed resistance element and a switch.

4. The resistance variable memory apparatus according to claim 1 , wherein the series resistance setting unit is configured to selectively turn on transistors included in a plurality of current paths which are provided on the series current path in parallel with each other, to set the resistance value of the series current path, the transistors having different ON-resistances; and

the parallel resistance setting unit is configured to selectively turn on transistors included in a plurality of current paths which are provided on the series current path in parallel with each other, to set the resistance value of the parallel current path, the transistors having different ON-resistances.

5. The resistance variable memory apparatus according to claim 1 , further comprising:

a controller;

wherein the controller is configured to control the series resistance setting unit and the parallel resistance setting unit based on a signal externally input, to set the resistance value of the series current path and the resistance value of the parallel current path, when the electric pulse application device outputs an electric pulse.

6. A write once resistance variable memory apparatus comprising:

a resistance variable element for storing data based on a change in an electric resistance;

an electric pulse application device including a first output terminal and a second output terminal, the electric pulse application device being configured to output an electric pulse between the first output terminal and the second output terminal;

a reference node;

a series current path for electrically connecting the first output terminal to the reference node;

a resistance change current path including the resistance variable element and electrically connecting the reference node to the second output terminal via the resistance variable element; and

a parallel current path for electrically connecting the reference node to the second output terminal in parallel with the resistance change current path;

wherein the resistance variable element has a characteristic in which the resistance variable element in a low-resistance state switches to a high-resistance state, a resistance value of which is higher than a resistance value of the low-resistance state, when a node potential which is a potential of the reference node based on the second output terminal as a reference is larger in absolute value than a first voltage level, and the resistance variable element in the high-resistance state switches from the high-resistance state to the low-resistance state when the node potential is larger in absolute value than a second voltage level which has a polarity identical to a polarity of the first voltage level and is larger in absolute value than the first voltage level;

wherein a resistance value of the series current path, a resistance value of the parallel current path, a resistance value of the resistance change current path in a state where the resistance variable element is in the high-resistance state, and a resistance value of the resistance change current path in a state where the resistance variable element is in the low-resistance state,

become resistance values at which the node potential is not smaller in absolute value than the first voltage level when the resistance variable element is in the low-resistance state and the electric pulse application device outputs a first electric pulse; and

become resistance values at which the node potential is not larger in absolute value than the second voltage level in a state where the electric pulse application device is outputting the first electric pulse after the resistance variable element has switched to the high-resistance state when the resistance variable element is in the low-resistance state and the electric pulse application device outputs the first electric pulse.

7. A write once resistance variable memory apparatus comprising:

a resistance variable element for storing data based on a change in an electric resistance;

an electric pulse application device including a first output terminal and a second output terminal, the electric pulse application device being configured to output an electric pulse between the first output terminal and the second output terminal;

a reference node,

a series current path for electrically connecting the first output terminal to the reference node;

a resistance change current path including the resistance variable element and electrically connecting the reference node to the second output terminal via the resistance variable element; and

a parallel current path for electrically connecting the reference node to the second output terminal in parallel with the resistance change current path;

wherein the resistance variable element has a characteristic in which the resistance variable element in a low-resistance state switches to a high-resistance state, a resistance value of which is higher than a resistance value of the low-resistance state, when a node potential which is a potential of the reference node based on the second output terminal as a reference is larger in absolute value than a first voltage level, and the resistance variable element in the high-resistance state switches from the high-resistance state to the low-resistance state when the node potential is larger in absolute value than a second voltage level which has a polarity identical to a polarity of the first voltage level and is larger in absolute value than the first voltage level;

wherein a resistance value of the series current path, a resistance value of the parallel current path, a resistance value of the resistance change current path in a state where the resistance variable element is in the high-resistance state, and a resistance value of the resistance change current path in a state where the resistance variable element is in the low-resistance state,

become resistance values at which the node potential is not smaller in absolute value than the second voltage level when the resistance variable element is in the high-resistance state and the electric pulse application device outputs a second electric pulse; and

become resistance values at which the node potential is not larger in absolute value than the first voltage level in a state where the electric pulse application device is outputting the second electric pulse after the resistance variable element has switched to the low-resistance state when the resistance variable element is in the high-resistance state and the electric pulse application device outputs the second electric pulse.

8. A write once resistance variable memory apparatus comprising:

a resistance variable element including a first resistance terminal and a second resistance terminal, the resistance variable element being configured to store data based on a change in an electric resistance between the first resistance terminal and the second resistance terminal;

an electric pulse application device including a first output terminal and a second output terminal, the electric pulse application device being configured to output an electric pulse between the first output terminal and the second output terminal;

a series current path for electrically connecting the first output terminal to the first resistance terminal; and

a resistance change current path including the resistance variable element and electrically connecting the first resistance terminal to the second output terminal via the resistance variable element;

wherein the resistance variable element has a characteristic in which the resistance variable element in a high-resistance state switches to a low-resistance state, a resistance value of which is lower than a resistance value of the high-resistance state, when a potential at a predetermined point on the series current path based on the second output terminal as a reference is larger in absolute value than a third voltage level, and the resistance variable element in the low-resistance state switches from the low-resistance state to the high-resistance state when the potential is larger in absolute value than a fourth voltage level which has a polarity identical to a polarity of the third voltage level and is smaller in absolute value than the third voltage level; and wherein

when a resistance value of the series current path is expressed as Rs,

a resistance value of the resistance change current path in a state where the resistance variable element is in the low-resistance state is expressed as Rrl,

a resistance value of the resistance change current path in a state where the resistance variable element is in the high-resistance state is expressed as Rrh,

an absolute value of a potential of the first output terminal based on the second output terminal as a reference which occurs when a third electric pulse is output, is expressed as V 3 ,

an absolute value of the third voltage level is expressed as Vhl′, and

an absolute value of the fourth voltage level is expressed as Vlh′, a formula (7) and a formula (8) expressed below are satisfied:

(

V

⁢

⁢

3

-

Vhl

′

)

×

Rrh

′

Vhl

′

≥

Rs

(

7

)

(

V

⁢

⁢

3

-

Vlh

′

)

×

Rrl

′

Vlh

′

<

Rs

.

(

8

)