Non-volatile SRAM cell
First Claim
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1. A static random access memory (SRAM), comprising:
- a cross coupled pair of inverters, wherein each inverter includes a p-type pull up transistor and an n-type pull down transistor coupled to a first static storage node, wherein gates of each inverter in the pair are coupled to the first static storage node of the other inverter; and
wherein each inverter includes a second non-volatile storage node coupled to the first static storage node, wherein the second storage node comprises a two terminal magnetic tunnel junction (MTJ) device, wherein the MTJ device includes;
a first unpinned ferromagnetic layer coupled to the first storage node such that a polarization of an associated spin value can rotate; and
a second pinned ferromagnetic layer in contact with an anti-ferromagnetic layer coupled to a control line such that a polarization of an associated spin value is fixed in one direction;
wherein the first unpinned ferromagnetic layer and the second pinned ferromagnetic layer are separated by a dielectric.
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Abstract
Methods, devices and systems for non-volatile static random access memory (SRAM) are provided. One method embodiment for operating an SRAM includes transferring data from a pair of static storage nodes of the SRAM to a pair of non-volatile storage nodes when the SRAM is placed in a standby mode. The method further includes transferring data from the pair of non-volatile storage nodes to the pair of static storage nodes when the SRAM exits the standby mode.
34 Citations
16 Claims
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1. A static random access memory (SRAM), comprising:
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a cross coupled pair of inverters, wherein each inverter includes a p-type pull up transistor and an n-type pull down transistor coupled to a first static storage node, wherein gates of each inverter in the pair are coupled to the first static storage node of the other inverter; and wherein each inverter includes a second non-volatile storage node coupled to the first static storage node, wherein the second storage node comprises a two terminal magnetic tunnel junction (MTJ) device, wherein the MTJ device includes; a first unpinned ferromagnetic layer coupled to the first storage node such that a polarization of an associated spin value can rotate; and a second pinned ferromagnetic layer in contact with an anti-ferromagnetic layer coupled to a control line such that a polarization of an associated spin value is fixed in one direction; wherein the first unpinned ferromagnetic layer and the second pinned ferromagnetic layer are separated by a dielectric. - View Dependent Claims (2)
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3. A method for operating a static random access memory (SRAM), comprising:
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transferring data from a pair of static storage nodes of the SRAM to a pair of non-volatile storage nodes when the SRAM is placed in a standby mode;
wherein the pair of non-volatile storage nodes comprise a pair of two terminal magnetic tunnel junction (MTJ) devices, and wherein the MTJ devices include;a first unpinned ferromagnetic layer coupled to the first storage node such that a polarization of an associated spin value can rotate; and a second pinned ferromagnetic layer in contact with an anti-ferromagnetic layer coupled to a control line such that a polarization of an associated spin value is fixed in one direction; wherein the first unpinned ferromagnetic layer and the second pinned ferromagnetic layer are separated by a dielectric; and transferring data from the pair of non-volatile storage nodes to the pair of static storage nodes when the SRAM exits the standby mode; wherein transferring data includes changing a potential applied to the pair of non-volatile storage nodes between a first potential and a second potential using a control circuit coupled by a control line to the pair of non-volatile storage nodes. - View Dependent Claims (4)
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5. A method for operating a static random access memory (SRAM), comprising:
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applying a first potential to a pair of non-volatile storage nodes coupled to a pair of static storage nodes of the SRAM in order to store data from the pair of static storage nodes to the pair of non-volatile storage nodes;
wherein the pair of non-volatile storages nodes comprise a pair of two terminal magnetic tunnel junction (MTJ) devices, and wherein the MJT devices include;a first unpinned ferromagnetic layer coupled to the first storage node such that a polarization of an associated spin value can rotate; and a second pinned ferromagnetic layer in contact with an anti-ferromagnetic layer coupled to a control line such that a polarization of an associated spin value is fixed in one direction; wherein the first unpinned ferromagnetic layer and the second pinned ferromagnetic layer are separated by a dielectric; applying a second potential to the pair of non-volatile storage nodes to return data from the pair of non-volatile storage nodes to the pair of static storage nodes; and applying a third potential to reset the pair of non-volatile storage nodes. - View Dependent Claims (6, 7, 8)
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9. A method for forming a memory, comprising:
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cross coupling a pair of inverters to form a static random access memory (SRAM) cell, each inverter including a p-type pull up transistor and an n-type pull down transistor coupled to a static storage node, wherein gates of each inverter in the pair are coupled to the static storage node of the other inverter; and connecting a pair of non-volatile storage nodes to a pair of static storage nodes by forming the pair of non-volatile storage nodes above a layer in which the static storage nodes of the SRAM are formed to conserve SRAM cell area;
wherein the pair of non-volatile storage nodes comprise a pair of two terminal magnetic tunnel junction (MTJ) devices, and wherein the MTJ devices include;a first unpinned ferromagnetic layer coupled to the first storage node such that a polarization of an associated spin value can rotate; and a second pinned ferromagnetic layer in contact with an anti-ferromagnetic layer coupled to a control line such that a polarization of an associated spin value is fixed in one direction; wherein the first unpinned ferromagnetic layer and the second pinned ferromagnetic layer are separated by a dielectric. - View Dependent Claims (10, 11, 12, 13)
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14. A method for operating a static random access memory (SRAM), comprising:
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transferring data from a pair of static storage nodes of the SRAM to a pair of non-volatile storage nodes when the SRAM is placed in a standby mode by coupling a ground to the pair of non-volatile storage nodes;
wherein the pair of non-volatile storage nodes comprise a pair of two terminal magnetic tunnel junction (MTJ) devices, and wherein the MTJ devices include;a first unpinned ferromagnetic layer coupled to the first storage node such that a polarization of an associated spin value can rotate; and a second pinned ferromagnetic layer in contact with an anti-ferromagnetic layer coupled to a control line such that a polarization of an associated spin value is fixed in one direction; wherein the first unpinned ferromagnetic layer and the second pinned ferromagnetic layer are separated by a dielectric; and transferring data from the pair of non-volatile storage nodes to the pair of static storage nodes when the SRAM exits the standby mode by coupling a first positive potential to the pair of non-volatile storage nodes. - View Dependent Claims (15, 16)
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Specification