A writing method, circuit and array

Abstract

The present application provides a writing method, circuit and array, and relates to the field of integrated circuit technology. The writing circuit includes a voltage control module and a Nand-type magnetic storage unit; the Nand-type magnetic storage unit includes a spin-orbit moment layer and a plurality of magnetic tunnel junctions arranged on the spin-orbit moment layer. The voltage control module is used to generate a writing voltage and a control voltage corresponding to a plurality of magnetic tunnel junctions according to a preset storage requirement, and provide the writing voltage to the spin-orbit moment layer, and provide the control voltage to the corresponding magnetic tunnel junction, so that the initialized plurality of magnetic tunnel junctions are flipped according to a preset flipping probability. The present application can control the flipping probability of the magnetic tunnel junction by generating a control voltage corresponding to each magnetic tunnel junction according to the preset storage requirement, so as to accurately realize the selective writing of the Nand-type magnetic storage unit, and further enable the Nand-type magnetic storage unit to be applied to precise storage.

Description

Technical Field

[0001] The present application relates to the technical field of integrated circuits, and in particular to a writing method, circuit and array. Background Art

[0002] With the demand for memory power consumption and writing speed, magnetic random access memory (MRAM) has become one of the promising next-generation memories.

[0003] MRAM written based on spin orbit torque (SOT) has the characteristics of read-write path separation, which can solve the existing problem of device wear and aging when writing data. At the same time, SOT-MRAM has faster writing speed and lower writing power consumption. However, since SOT-MRAM needs to set switch tubes at the write and read ports for read and write control, the integration density of SOT-MRAM is limited. Based on this, the Nand-type SOT-MRAM cell adopts a structure of placing multiple MTJs on the SOT bottom electrode to improve the integration density of SOT-MRAM. At the same time, the structure of multiple MTJs sharing the SOT bottom electrode can save the number of transistors in the write channel, thereby reducing the footprint of a single storage unit.

[0004] Nand-type SOT-MRAM achieves data writing by gating multiple MTJs. The gating of MTJ is mainly based on the spin current in the SOT layer and the voltage controlled magnetic anisotropy (VCMA) voltage. However, the current regulation of the VCMA voltage of multiple MTJs is relatively complicated, making it difficult to achieve selective writing in the Nand-type SOT device array, which in turn makes it difficult for Nand-type SOT devices to be used in precision storage. Summary of the invention

[0005] The present application provides a writing method, a circuit and an array, which are used to provide a technical solution capable of accurately realizing the selective writing of Nand-type magnetic storage cells.

[0006] In a first aspect, the present application provides a write circuit, including a voltage control module and a Nand-type magnetic storage unit; the Nand-type magnetic storage unit includes a spin-orbit moment layer and a plurality of magnetic tunnel junctions arranged on the spin-orbit moment layer.

[0007] The voltage control module is used to generate a write voltage and a control voltage corresponding to multiple magnetic tunnel junctions according to preset storage requirements, and provide the write voltage to the spin-orbit moment layer and the control voltage to the corresponding magnetic tunnel junction, so that the initialized multiple magnetic tunnel junctions are flipped according to the preset flipping probability.

[0008] In one possible implementation, the voltage control module is specifically used to classify multiple magnetic tunnel junctions according to preset storage requirements, and determine the write voltage and the control voltage corresponding to the multiple magnetic tunnel junctions according to the classification results of the multiple magnetic tunnel junctions.

[0009] In a possible implementation, the classification results of the multiple magnetic tunnel junctions include a first storage requirement magnetic tunnel junction and / or a second storage requirement magnetic tunnel junction.

[0010] Under a write voltage and a corresponding control voltage, the first storage requirement magnetic tunnel junction has a first switching probability, and the second storage requirement magnetic tunnel junction has a second switching probability.

[0011] The first flip probability is greater than the second flip probability.

[0012] In a possible implementation, the first storage requirement magnetic tunnel junction is used to store a first type of storage data, and the first storage requirement magnetic tunnel junction is used to store a second type of storage data, and the accuracy of the first type of storage data is greater than the accuracy of the second type of storage data.

[0013] In a possible implementation, the circuit further includes two first switch tubes and a plurality of second switch tubes, the two first switch tubes are respectively connected to two ends of the spin-orbit moment layer, and the plurality of second switch tubes are connected to the tops of the plurality of magnetic tunnel junctions in a one-to-one correspondence;

[0014] The voltage control module includes a first voltage control unit and a plurality of second voltage control units which are arranged in one-to-one correspondence with the plurality of magnetic tunnel junctions.

[0015] The first voltage control unit is used to provide a write voltage to the spin-orbit moment layer through a first switch tube.

[0016] Each second voltage control unit is used to provide a corresponding control voltage to a corresponding magnetic tunnel junction through a corresponding second switch tube.

[0017] In a possible implementation, the circuit further includes two first switch tubes and one second switch tube, the two first switch tubes are respectively connected to two ends of the spin-orbit moment layer, and the second switch tube is connected to the tops of the multiple magnetic tunnel junctions.

[0018] The voltage control module includes a first voltage control unit and a second voltage control unit.

[0019] The first voltage control unit is used to provide a write voltage to the spin-orbit moment layer through a first switch tube.

[0020] The second voltage control unit is used to provide a control voltage to the plurality of magnetic tunnel junctions through the second switch tube.

[0021] In a second aspect, the present application provides a write array, comprising a plurality of write circuits arranged in a matrix as described in any one of the first aspects.

[0022] In a second aspect, the present application provides a writing method, which is applied to a Nand-type magnetic storage unit, wherein the Nand-type magnetic storage unit includes a spin-orbit moment layer and a plurality of magnetic tunnel junctions arranged on the spin-orbit moment layer.

[0023] The write methods include:

[0024] According to preset storage requirements, a plurality of magnetic tunnel junctions are classified into first storage requirement magnetic tunnel junctions and second storage requirement magnetic tunnel junctions.

[0025] According to the classification results of multiple magnetic tunnel junctions, a write voltage and a control voltage corresponding to the multiple magnetic tunnel junctions are determined. Under the write voltage and the corresponding control voltage, the first storage requirement magnetic tunnel junction has a first flipping probability, and the second storage requirement magnetic tunnel junction has a second flipping probability, wherein the first flipping probability is greater than the second flipping probability.

[0026] A write voltage is provided to the spin-orbit moment layer, and a control voltage is provided to the corresponding magnetic tunnel junction, so that the initialized multiple magnetic tunnel junctions are flipped according to a preset flip probability.

[0027] In a possible implementation, determining the write voltage of the Nand-type magnetic storage unit and the control voltages corresponding to the multiple magnetic tunnel junctions according to the classification results of the multiple magnetic tunnel junctions includes:

[0028] Determining a write voltage according to the number of magnetic tunnel junctions with a first storage requirement among the plurality of magnetic tunnel junctions;

[0029] According to the write voltage and the classification result of the magnetic tunnel junction, the control voltage corresponding to the magnetic tunnel junction is determined.

[0030] In a possible implementation, the magnitude of the write voltage is proportional to the number of the first storage requirement magnetic tunnel junctions among the plurality of magnetic tunnel junctions;

[0031] The control voltage of the first storage requirement magnetic tunnel junction is in inverse proportion to the distance between the first storage requirement magnetic tunnel junction and the write voltage terminal of the Nand type magnetic storage unit.

[0032] In the case of adopting the above technical solution, the voltage control module provided by the present application can generate a write voltage and a control voltage corresponding to a plurality of magnetic tunnel junctions according to a preset storage requirement, and provide the write voltage to the spin-orbit moment layer, and provide the control voltage to the corresponding magnetic tunnel junction. At this time, according to the direction in which the write voltage is provided, the voltage at the bottom of the plurality of magnetic tunnel junctions on the spin-orbit moment layer gradually changes, that is, the voltage at the bottom of the plurality of magnetic tunnel junctions is related to its position on the spin-orbit moment layer, based on which the VCMA voltage between the top and the bottom of each magnetic tunnel junction is different, so the flip voltage corresponding to each magnetic tunnel junction is also different, therefore, the present application can control the flip probability of the magnetic tunnel junction according to the control voltage corresponding to each magnetic tunnel junction generated according to the preset storage requirement, so as to accurately realize the selective writing of the Nand-type magnetic storage unit, and then enable the Nand-type magnetic storage unit SOT device to be applied to precise storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0034] Figure 1 A circuit structure diagram of a write circuit provided in an embodiment of the present application;

[0035] Figure 2 A circuit structure diagram of a specific write circuit provided in an embodiment of the present application;

[0036] Figure 3 A circuit structure diagram of another specific write circuit provided in an embodiment of the present application;

[0037] Figure 4 A circuit structure diagram of another writing circuit provided in an embodiment of the present application.

[0038] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0039] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. It is understood that the terms "first", "second", etc. used in the present application can be used to describe various information or data in this article, but these elements are not limited by these terms. These terms are only used to distinguish the first information from another information. For example, without departing from the scope of the present application, the first action information can be referred to as the second action information, and similarly, the second action information can be referred to as the first action information. Both the first action information and the second action information are action information, but they are not the same action information.

[0041] Before describing the technical solution provided by the embodiments of the present application, the following section first describes in detail the background and application scenarios of the technical solution of the present application:

[0042] With the demand for memory power consumption and writing speed, magnetic random access memory (MRAM) has become one of the promising next-generation memories.

[0043] MRAM written based on spin orbit torque (SOT) has the characteristics of read-write path separation, which can solve the existing problem of device wear and aging when writing data. At the same time, SOT-MRAM has faster writing speed and lower writing power consumption. However, since SOT-MRAM needs to set switch tubes at the write and read ports for read and write control, the integration density of SOT-MRAM is limited. Based on this, the Nand-type SOT-MRAM cell adopts a structure of placing multiple MTJs on the SOT bottom electrode to improve the integration density of SOT-MRAM. At the same time, the structure of multiple MTJs sharing the SOT bottom electrode can save the number of transistors in the write channel, thereby reducing the footprint of a single storage unit.

[0044] Nand-type SOT-MRAM achieves data writing by gating multiple MTJs. The gating of MTJ is mainly based on the spin current in the SOT layer and the voltage controlled magnetic anisotropy (VCMA) voltage. However, the current regulation of the VCMA voltage of multiple MTJs is relatively complicated, making it difficult to achieve selective writing in the Nand-type SOT device array, which in turn makes it difficult for Nand-type SOT devices to be used in precision storage.

[0045] The above VCMA can be explained as follows: Based on the electric field effect, by applying voltage between the magnetic material and the insulating layer, the accumulation or depletion of electrons at the interface is changed, thereby affecting the perpendicular magnetic anisotropy of the magnetic material. Specifically, the voltage changes the charge distribution at the interface of the magnetic material, and this change affects the perpendicular magnetic anisotropy energy of the magnetic material. In other words, VCMA uses voltage to adjust the perpendicular magnetic anisotropy of the magnetic material, reduce or increase the energy barrier for the reversal of the free layer magnetic moment, and thus achieve more efficient and low-power control.

[0046] Based on this, the present application provides a technical solution for adjusting the control voltage of MTJs at different positions / areas so that MTJs at different positions / areas are subjected to different longitudinal voltage differences, so that different MTJs have different flipping probabilities, and accurate (higher flipping probability) writing is achieved for MTJs in the required area, and approximate writing (lower flipping probability) is achieved for MTJs in other areas. This technical solution can be used to characterize floating-point numbers and constitute weights in neural networks; it can also be used for approximate storage. And this technical solution can reduce power consumption and area overhead, and reduce the requirements for gating.

[0047] The following section is used to describe in detail the technical solutions provided by the embodiments of the present application.

[0048] First, refer to Figure 1 The embodiment of the present application provides a writing circuit, which includes a voltage control module 20 and a Nand type magnetic storage unit 10. The Nand type magnetic storage unit 10 includes a spin-orbit moment layer 101 and a plurality of magnetic tunnel junctions 102 arranged on the spin-orbit moment layer.

[0049] The above-mentioned voltage control module 20 is used to generate a write voltage and a control voltage corresponding to multiple magnetic tunnel junctions 102 according to preset storage requirements, and provide the write voltage to the spin-orbit moment layer 101, and provide the corresponding control voltage to the magnetic tunnel junction 102, so that the initialized multiple magnetic tunnel junctions 102 can be flipped according to the preset flipping probability.

[0050] It should be understood that the above preset storage requirement can be set according to the actual storage requirement. For example, when the actual storage requirement is to use Nand-type magnetic storage units to store floating point weights, the preset storage requirement can be high-bit precision and low-bit approximation.

[0051] For another example, when the actual storage requirement is to use a Nand-type magnetic storage unit to store pixel data, the preset storage requirement can be determined based on the actual pixel accuracy. The preset storage requirement can be that high-precision pixels correspond to precise storage and low-precision pixels correspond to approximate storage.

[0052] Initializing the multiple magnetic tunnel junctions may include applying an initialization voltage to both ends of the spin-orbit moment layer. After applying the initialization voltage, the entire Nand-type magnetic storage unit may be erased to an initial state, that is, the multiple MTJ states are consistent. For example, the multiple MTJs may be in a low resistance state.

[0053] The voltage control module provided in the embodiment of the present application can generate a write voltage and a control voltage corresponding to a plurality of magnetic tunnel junctions according to a preset storage requirement, and provide the write voltage to the spin-orbit moment layer, and provide the control voltage to the corresponding magnetic tunnel junction. At this time, according to the direction in which the write voltage is provided, the voltage at the bottom of the plurality of magnetic tunnel junctions on the spin-orbit moment layer gradually decreases, that is, the voltage at the bottom of the plurality of magnetic tunnel junctions is related to its position on the spin-orbit moment layer, based on which the VCMA voltage between the top and the bottom of each magnetic tunnel junction is different, so the flip voltage corresponding to each magnetic tunnel junction is also different, therefore, the present application can control the flip probability of the magnetic tunnel junction according to the control voltage corresponding to each magnetic tunnel junction generated according to the preset storage requirement, so as to accurately realize the selective writing of the Nand-type magnetic storage unit, and then enable the Nand-type magnetic storage unit to be applied to precise storage.

[0054] As a specific embodiment, refer to Figure 1 The Nand-type magnetic storage unit 10 comprises a spin-orbit moment layer 101 and eight magnetic tunnel junctions 102 on the spin-orbit moment layer 101. It should be understood that the number of magnetic tunnel junctions 102 may be other, and the embodiment of the present application does not make a special number of magnetic tunnel junctions 102.

[0055] The voltage control module 20 can apply a write voltage to one end (the left side in the figure) of the spin-orbit moment layer 101 , and the other end (the right side in the figure) of the spin-orbit moment layer 101 maintains a low potential.

[0056] The voltage control module 20 may apply a control voltage to each magnetic tunnel junction 102 so that each magnetic tunnel junction has a different flipping probability.

[0057] Optional, see Figure 1Taking writing from a low resistance state to a high resistance state as an example, a write voltage is applied to the self-spin track moment layer 101 from one end of the self-spin track moment layer 101, and a corresponding control voltage is applied to the tops of multiple magnetic tunnel junctions 102 at the same time. The voltage difference between the top and bottom of the magnetic tunnel junction 102 represents the magnitude of the VCMA voltage, and the voltage at the bottom of the MTJ is related to the position. Assuming that the potential at one end of the self-spin track moment layer 101 is a high potential, the other end of the self-spin track moment layer 101 is a low potential, then the potential at the bottom of the MTJ from left to right is from high to low. At this time, the VCMA voltage between the top and bottom of each MTJ can be regulated by regulating the control voltage applied to each magnetic tunnel junction, so that the flipping of each MTJ has a flipping probability that meets the preset storage requirements.

[0058] The above part is used to describe the technical solution provided by the embodiment of the present application in an overall summary manner, and the following part is used to describe in detail how the voltage control module determines the write voltage and the control voltages corresponding to multiple magnetic tunnel junctions.

[0059] Optionally, the voltage control module is specifically used to classify multiple magnetic tunnel junctions according to preset storage requirements, and determine the write voltage and the control voltage corresponding to the multiple magnetic tunnel junctions according to the classification results of the multiple magnetic tunnel junctions.

[0060] It should be understood that the above classification can be used to classify multiple magnetic tunnel junctions into precisely controlled magnetic tunnel junctions and approximately controlled magnetic tunnel junctions, wherein the flip probability of the precisely controlled magnetic tunnel junction is greater, and the flip probability of the approximately controlled magnetic tunnel junction is smaller. In some cases, it can be considered that under the combined effect of the applied control voltage and the write voltage, the precisely controlled magnetic tunnel junction can achieve flipping, while the flip probability of the approximately controlled magnetic tunnel junction is smaller.

[0061] In some examples, the classification result of the plurality of magnetic tunnel junctions may include a first storage requirement magnetic tunnel junction, and / or a second storage requirement magnetic tunnel junction.

[0062] When data is written, under the write voltage and the corresponding control voltage, the first storage requirement magnetic tunnel junction has a first flip probability, and the second storage requirement magnetic tunnel junction has a second flip probability.

[0063] The first flip probability is greater than the second flip probability.

[0064] It is worth noting that the first flip probability in the embodiment of the present application can be close to 100% to achieve precise control of the flipping of the magnetic tunnel junction, while the second flip probability is smaller and can be used to achieve approximate control of the flipping of the magnetic tunnel junction. Based on this, the write circuit provided in the embodiment of the present application can be applied to pixel storage in image processing. When high-precision pixel storage is required, the first storage requirement magnetic tunnel junction can be used for storage. When low-precision pixel storage is required, the second storage requirement magnetic tunnel junction can be used for storage.

[0065] It should be understood that the control voltage corresponding to the magnetic tunnel junction of the first storage requirement needs to be regulated based on the VCMA effect, combined with the position of the magnetic tunnel junction of the first storage requirement in the spin-orbit moment layer, and the write voltage. As for the control voltage corresponding to the magnetic tunnel junction of the second storage requirement, the embodiment of the present application does not need to perform special regulation on it. Based on this, the complexity of voltage regulation by the voltage regulation module can be reduced.

[0066] As an example, see Figure 1 There are 8 MTJs on the SOT. From left to right, the serial numbers can be 0-7. Assuming that MTJ0-3 (four on the left) are magnetic tunnel junctions with the first storage requirement, and MTJ4-7 (four on the right) are magnetic tunnel junctions with the second storage requirement, at this time, it is necessary to regulate the write voltage and the control voltage required by the four MTJs on the left based on the VCMA effect, so that the magnetic tunnel junction with the first storage requirement has the first flip probability. For the four magnetic tunnel junctions with the second storage requirement on the right, when regulating the write voltage, it is not necessary to consider whether it can be flipped, and it is not necessary to regulate its control voltage according to the write voltage, so as to reduce the complexity of the voltage regulation module in regulating the control voltage.

[0067] According to the above description, the flip probability of each magnetic tunnel junction is related to the write voltage and the corresponding control voltage. The control voltage is determined based on the VCMA effect and the write voltage. Therefore, when the write voltage is determined, the control voltage corresponding to the magnetic tunnel junction that needs to be accurately stored can be precisely regulated according to the storage requirements of the magnetic tunnel junction, and the control voltage corresponding to the magnetic tunnel junction that needs to be approximately stored does not need to be regulated.

[0068] Optionally, when all MTJs are first storage demand magnetic tunnel junctions, the corresponding write voltage and the control voltage applied to each magnetic tunnel junction can be obtained through the above principle and the withstand voltage parameter of the Nand type magnetic storage unit.

[0069] The determination of the write voltage can be explained as follows:

[0070] It should be understood that when the write voltage is applied to the spin-orbit moment layer, a spin current will be generated in the spin-orbit moment layer, and when the spin current is applied to the magnetic tunnel junction, it is used to change its magnetization direction to achieve data storage. For a magnetic tunnel junction of a certain structure, the required spin current is certain.

[0071] It should be further understood that the spin current generated by the write voltage needs to change the magnetization direction of the first storage requirement magnetic tunnel junction so that multiple first storage requirement magnetic tunnel junctions can achieve accurate storage during the write process. Based on the above description, the write voltage can be determined according to the structure of the spin-orbit moment layer and the number of first storage requirement magnetic tunnel junctions.

[0072] In one example, the first storage requirement magnetic tunnel junction can be used to store a first type of storage data, and the second storage requirement magnetic tunnel junction can be used to store a second type of storage data, wherein the accuracy of the first type of storage data is greater than the accuracy of the second type of storage data.

[0073] That is to say, the first type of stored data has a higher precision and can be used for weights in neural networks or other values ​​that require high precision. The second type of stored data has a lower precision requirement and can be used to store intermediate calculation results or other data that does not require high precision.

[0074] Based on the above description, this embodiment can flexibly adjust the storage accuracy of multiple magnetic tunnel junctions according to the accuracy requirements of different data to improve the utilization efficiency of the write circuit. It is also possible to improve the overall performance and power consumption efficiency by optimizing the classification results of multiple magnetic tunnel junctions. Therefore, this embodiment can be applied to applications that need to process high-precision and low-precision data at the same time, such as neural networks and machine learning.

[0075] It should be understood that in order to achieve precise control of the writing process of the Nand-type magnetic storage unit, the writing circuit in this embodiment may also adopt the following scheme;

[0076] In some examples, reference Figure 2 The above-mentioned writing circuit may further include two first switch tubes S1 and multiple second switch tubes S2, the two first switch tubes S1 are respectively connected to the two ends of the spin-track moment layer 101, and the multiple second switch tubes S2 are connected to the multiple magnetic tunnel junctions 102 in a one-to-one correspondence.

[0077] The two first switch tubes S1 are respectively connected to the two ends of the spin-orbit moment layer 101, and are used to control the direction and magnitude of the write voltage through the spin-orbit moment layer 101. When the write voltage is applied to the SOT layer, a spin current is generated, and the spin current is applied to the magnetic tunnel junction to change its magnetization direction.

[0078] The plurality of second switch tubes S2 are respectively connected to a plurality of magnetic tunnel junctions 102 for selecting a corresponding magnetic tunnel junction so that, under the action of a corresponding control voltage and a write voltage, the magnetic tunnel junction 102 stores data according to preset storage requirements.

[0079] Based on this, the embodiment of the present application can accurately control the write operation through the combination of the first switch tube and the second switch tube, and select a specific magnetic tunnel junction to achieve a precise write operation.

[0080] Exemplarily, the first switch tube and the second switch tube may be any one of a bipolar transistor (BJT, Bipolar Junction Transistor), a field effect transistor (FET, Field-Effect Transistor), an insulated gate bipolar transistor (IGBT, Insulated Gate Bipolar Transistor), etc., and the embodiments of the present application do not specifically limit this.

[0081] The voltage control module includes a first voltage control unit 201 and a plurality of second voltage control units arranged in one-to-one correspondence with the plurality of magnetic tunnel junctions. The first voltage control unit is used to provide a write voltage to the spin-orbit moment layer through a first switch tube. Each second voltage control unit is used to provide a corresponding control voltage to a corresponding magnetic tunnel junction through a corresponding second switch tube.

[0082] The first voltage control unit and the second voltage control unit may be an adjustable voltage regulator or a DAC (digital-to-analog converter) for providing accurate write voltage and control voltage.

[0083] In this embodiment, the current passing through the SOT layer can be controlled by adjusting the output voltage of the first voltage control unit, thereby generating the required spin current. The storage accuracy of multiple magnetic tunnel junctions can be accurately controlled by adjusting the output voltage of the second voltage control unit, thereby improving the reliability and efficiency of the write operation.

[0084] In summary, the embodiment of the present application utilizes a first voltage control unit and multiple second voltage control units to control the write voltage of the spin-orbit moment layer and the control voltages corresponding to multiple magnetic tunnel junctions, thereby achieving efficient, low-power and precise write operations.

[0085] It should be understood that the write circuit in this example can be applied to application scenarios where each magnetic tunnel junction needs to be precisely controlled, and can also be applied to application scenarios where some magnetic tunnel junctions need to be precisely controlled and other magnetic tunnel junctions need to be approximately controlled.

[0086] It should be further understood that for a magnetic tunnel junction that needs to be precisely controlled, the corresponding second voltage control unit needs to determine the output control voltage in combination with the write voltage output by the first voltage control module and the position of the magnetic tunnel junction on the spin-orbit junction. For a magnetic tunnel junction that is approximately controlled, the corresponding second voltage control unit can provide it with a predetermined reference voltage without the need for complex control operations, thereby reducing the complexity of the operation and saving the time required for writing. In particular, when determining the predetermined reference voltage, there is no need to consider whether the magnetic tunnel junction can be flipped, and only whether the reference voltage will cause damage to the Nand-type magnetic storage unit can be considered.

[0087] In other examples, refer to Figure 3 The above-mentioned writing circuit may further include two first switch tubes S1 and one second switch tube S2 , wherein the two first switch tubes S1 are respectively connected to two ends of the spin-track moment layer 101 , and the second switch tube S2 is connected to the top of the plurality of magnetic tunnel junctions 102 .

[0088] Similarly, the two first switch tubes S1 are connected to the two ends of the SOT layer respectively, and are used to control the direction and magnitude of the write voltage through the SOT layer. When the write voltage is applied to the SOT layer, a spin current will be generated, and this spin current will be applied to the selected magnetic tunnel junction, which can change the magnetization direction of the magnetic tunnel junction.

[0089] The second switch tube S2 is respectively connected to the tops of multiple magnetic tunnel junctions, and is used to provide the same control voltage to the multiple magnetic tunnel junctions, so that the magnetic tunnel junctions store data according to preset storage requirements.

[0090] Exemplarily, the first switch tube S1 and the second switch tube S2 may be any one of a bipolar transistor (BJT, Bipolar Junction Transistor), a field effect transistor (FET, Field-Effect Transistor), an insulated gate bipolar transistor (IGBT, Insulated Gate Bipolar Transistor), etc., and the embodiments of the present application do not specifically limit this.

[0091] It should be understood that, compared with the previous example, this example includes only one second switch tube S2. Since fewer switch tubes are used, the circuit design and control logic can be simplified and the degree of circuit integration can be improved.

[0092] The voltage control module includes a first voltage control unit 201 and a second voltage control unit 202 .

[0093] The first voltage control unit 201 is used to provide a write voltage to the spin-track moment layer 101 through the first switch tube S1.

[0094] The second voltage control unit 202 is used to provide the same control voltage to the multiple magnetic tunnel junctions 102 through the second switch tube S2.

[0095] The first voltage control unit 201 and the second voltage control unit 202 may be an adjustable voltage regulator or a DAC (digital-to-analog converter), which are used to provide accurate write voltage and control voltage respectively.

[0096] In this embodiment, the current passing through the SOT layer can be controlled by adjusting the output voltage of the first voltage control unit, thereby generating the desired spin current. The flip probability of multiple magnetic tunnel junctions is controlled by adjusting the control voltage output by the second voltage control unit. It should be understood that since the multiple magnetic tunnel junctions in the present application use the same control voltage, the flip probability of multiple MTJs gradually decreases according to the direction of the write voltage.

[0097] Based on this, this example can be used in neural network calculations, and each MTJ flip probability can correspond to a different calculation weight, thereby achieving approximate calculations. In this example, multiple MTJs are connected to the same second voltage control unit, multiple MTJs have a common potential, and the flip probabilities of multiple MTJs gradually decrease. Therefore, this example can be specifically applied to approximate calculations of neural networks, requiring scenarios where the flip probabilities of multiple MTJs gradually decrease.

[0098] As a specific example, see Figure 4 , the write circuit can be applied to approximate calculation and storage weights. The Nand-type magnetic storage unit may include 8 magnetic tunnel junctions 102. The four left magnetic tunnel junctions 102 form an HSB unit 11 for storing high-bit data, and the four right magnetic tunnel junctions 102 form an LSB unit 12 for storing low-bit data. The tops of the magnetic tunnel junctions in the HSB unit 11 and the LSB unit 12 are equipotential. When current flows through the SOT bottom electrode, the magnetic tunnel junctions at different positions are subjected to different longitudinal currents, resulting in different flipping probabilities. The control voltage applied to the top of the magnetic tunnel junction is regulated so that the four left magnetic tunnel junctions can achieve precise storage, and the four right magnetic tunnel junctions 102 can achieve precise storage. For example, in the traditional VGG-8 neural network, 8 bits of synaptic weight (≈ a floating point number) are stored in 8 magnetic tunnel junctions of the Nand-type SOT-MRAM, each of which is used to store 1 bit of synaptic weight (≈ 1 bit of the floating point number). The first 4 magnetic tunnel junctions can guarantee the deterministic writing of the stored weights, so the first 4 bits of the synaptic weight (≈ the first N bits of the floating point number) are accurate, and the last 4 magnetic tunnel junctions cannot guarantee the deterministic writing of the stored weights, so the last 4 bits of the synaptic weight are inaccurate.

[0099] In a second aspect, an embodiment of the present application further provides a write array, comprising a plurality of write circuits arranged in a matrix as described in any one of the first aspects.

[0100] It should be understood that since the write array includes the above-mentioned write circuit, the beneficial effects of the write array and the write circuit provided in the embodiment of the first aspect are the same, which will not be repeated here.

[0101] As a specific example, the write array can be applied to approximate storage and may include two of the above-mentioned write circuits, and the Nand-type magnetic storage unit in each write circuit may include 4 magnetic tunnel junctions. One of the Nand-type magnetic storage units is an HSB unit for storing high-bit data, and the other Nand-type magnetic storage unit is an LSB unit for storing low-bit data. The gating and write probability of the HSB unit and the LSB unit can be controlled. Among them, the WER (Write Error Rate) value range of each magnetic tunnel junction in the HSB and LSB can range from 1E-6 to 1E-2. Furthermore, the LSB can be used for accurate storage or for approximate storage. This example can be used to store pixel data.

[0102] In a third aspect, an embodiment of the present application further provides a writing method, including: being applied to a Nand-type magnetic storage unit, wherein the Nand-type magnetic storage unit includes a spin-orbit moment layer and a plurality of magnetic tunnel junctions arranged on the spin-orbit moment layer.

[0103] The write methods include:

[0104] According to preset storage requirements, a plurality of magnetic tunnel junctions are classified into first storage requirement magnetic tunnel junctions and second storage requirement magnetic tunnel junctions.

[0105] It should be understood that the above classification can be used to divide multiple magnetic tunnel junctions into precisely controlled magnetic tunnel junctions and approximately controlled magnetic tunnel junctions, wherein the flip probability of the precisely controlled magnetic tunnel junction is greater, and the flip probability of the approximately controlled magnetic tunnel junction is smaller. In some cases, it can be considered that under the action of the control voltage and the write voltage, the precisely controlled magnetic tunnel junction can be flipped, while the flip probability of the approximately controlled tunnel junction is smaller.

[0106] According to the classification results of multiple magnetic tunnel junctions, a write voltage and a control voltage corresponding to the multiple magnetic tunnel junctions are determined. Under the write voltage and the corresponding control voltage, the first storage requirement magnetic tunnel junction has a first flipping probability, and the second storage requirement magnetic tunnel junction has a second flipping probability, wherein the first flipping probability is greater than the second flipping probability.

[0107] It is worth noting that the first flip probability in the embodiment of the present application is close to 100%, which can achieve precise control, while the second flip probability is small and cannot achieve precise control. Based on this, the write circuit provided in the embodiment of the present application can be applied to pixel storage in image processing. When high-precision pixel storage is required, the first storage requirement magnetic tunnel junction can be used for storage. When low-precision pixel storage is required, the second storage requirement magnetic tunnel junction can be used for storage.

[0108] A write voltage is provided to the spin-orbit moment layer, and a control voltage is provided to the corresponding magnetic tunnel junction, so that the initialized multiple magnetic tunnel junctions are flipped according to a preset flip probability.

[0109] Based on the above description, this embodiment can flexibly adjust the storage accuracy of multiple magnetic tunnel junctions according to the accuracy requirements of different data to improve the utilization efficiency of the write circuit. It is also possible to improve the overall performance and power consumption efficiency by optimizing the classification results of multiple magnetic tunnel junctions. Therefore, this embodiment can be applied to applications that need to process high-precision and low-precision data at the same time, such as neural networks and machine learning.

[0110] In a possible implementation, determining the write voltage of the Nand-type magnetic storage unit and the control voltages corresponding to the multiple magnetic tunnel junctions according to the classification results of the multiple magnetic tunnel junctions includes:

[0111] The write voltage is determined according to the number of first storage requirement magnetic tunnel junctions among the plurality of magnetic tunnel junctions.

[0112] It should be understood that when the write voltage is applied to the spin-orbit moment layer, a spin current is generated in the spin-orbit moment layer, and when the spin current is applied to the magnetic tunnel junction, it is used to change its magnetization direction to achieve data storage. For a magnetic tunnel junction of a certain structure, the required spin current is certain.

[0113] The first storage requirement magnetic tunnel junction corresponds to precise storage, and it is necessary to precisely control the magnetic tunnel junction of this type of storage requirement, so the write voltage can be determined according to the number of the first storage requirement magnetic tunnel junctions. The spin current generated by the write voltage needs to change the magnetization direction of the first storage requirement magnetic tunnel junction, so that during the writing process, multiple first storage requirement magnetic tunnel junctions can achieve accurate storage.

[0114] In one example, the magnitude of the write voltage is proportional to the number of the first storage requirement magnetic tunnel junctions among the plurality of magnetic tunnel junctions.

[0115] It should be further understood that when the number of first storage requirement magnetic tunnel junctions on the spin-orbit moment layer increases, the size of the spin-orbit moment layer will increase along the layout direction of the multiple magnetic tunnel junctions, and accordingly, its resistance will also increase, while the spin current required by the magnetic tunnel junction remains unchanged. Therefore, it is necessary to increase the write voltage to ensure that the current in the spin-orbit moment layer meets the spin current.

[0116] Based on the above description, when the number of magnetic tunnel junctions with the first storage requirement among multiple magnetic tunnel junctions is large, the corresponding write voltage is large, and when the number of magnetic tunnel junctions with the first storage requirement among multiple magnetic tunnel junctions is small, the corresponding write voltage is small.

[0117] The above section describes the determination of the write voltage.

[0118] After the write voltage is determined, the control voltage of each magnetic tunnel junction can be accurately controlled.

[0119] Optionally, a control voltage corresponding to the magnetic tunnel junction is determined according to the write voltage and the classification result of the magnetic tunnel junction.

[0120] It should be understood that the control voltage corresponding to the first storage requirement magnetic tunnel junction can be regulated based on the VCMA effect, combined with the position of the first storage requirement magnetic tunnel junction in the spin-orbit moment layer, and the write voltage. Specifically, based on the write voltage, the lower voltage of the first storage requirement magnetic tunnel junction can be obtained, and then based on the VCMA effect, the control voltage of the first storage requirement magnetic tunnel junction is determined to enable the first storage requirement magnetic tunnel junction to be flipped.

[0121] Based on this, the magnetic tunnel junction required for the first storage can be precisely controlled to achieve precise storage.

[0122] Optionally, the control voltage of the first storage requirement magnetic tunnel junction is inversely proportional to the distance between the first storage requirement magnetic tunnel junction and the write voltage terminal of the Nand-type magnetic storage unit.

[0123] That is to say, the control voltage of the first storage demand magnetic tunnel junction that is farther from the write voltage terminal is smaller than the control voltage of the first storage demand magnetic tunnel junction that is closer to the write voltage terminal. It should be understood that after the write voltage is applied to the write voltage terminal, the current at each position of the spin-orbit moment layer is consistent, but due to the different positions, the voltage at each position of the spin-orbit moment layer gradually decreases with the write voltage terminal as the starting point, that is, with the write voltage terminal as the starting point, the bottom voltage of the first storage demand magnetic tunnel junction gradually decreases, and the control voltage required for each first storage demand magnetic tunnel junction is the same, so according to the distance relative to the write voltage terminal, the control voltage of the first storage demand magnetic tunnel junction also gradually decreases.

[0124] Based on the above description, the embodiment of the present application can generate a write voltage and a control voltage corresponding to a plurality of magnetic tunnel junctions according to a preset storage requirement, and provide the write voltage to the spin-orbit moment layer, and provide the corresponding control voltage to the magnetic tunnel junction. At this time, according to the direction in which the write voltage is provided, the voltage at the bottom of the plurality of magnetic tunnel junctions on the spin-orbit moment layer gradually decreases, and the control voltage required for the plurality of magnetic tunnel junctions is the same. Based on this, the flip voltage corresponding to each magnetic tunnel junction also gradually decreases. Therefore, the embodiment of the present application can accurately control the data storage of the first storage requirement magnetic tunnel junction according to the control voltage corresponding to each first storage requirement magnetic tunnel junction determined according to the preset storage requirement, thereby enabling the Nand-type magnetic storage unit to be applied to precise storage.

[0125] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A writing circuit, characterized in that: It includes a voltage control module and a Nand-type magnetic storage unit; the Nand-type magnetic storage unit includes a spin-orbit moment layer and a plurality of magnetic tunnel junctions arranged on the spin-orbit moment layer; The voltage control module is used for: According to a preset storage requirement, the plurality of magnetic tunnel junctions are classified; the classification result of the plurality of magnetic tunnel junctions includes a first storage requirement magnetic tunnel junction and a second storage requirement magnetic tunnel junction; Determine a write voltage and a control voltage corresponding to the magnetic tunnel junction according to the number of the first storage requirement magnetic tunnel junctions among the plurality of magnetic tunnel junctions and the classification results of the plurality of magnetic tunnel junctions; Providing the write voltage to the spin-orbit moment layer and providing the control voltage to the corresponding magnetic tunnel junction; Under the write voltage and the corresponding control voltage, the first storage requirement magnetic tunnel junction has a first flip probability, and the second storage requirement magnetic tunnel junction has a second flip probability; The first flip probability is greater than the second flip probability.

2. The writing circuit according to claim 1, characterized in that: The first storage requirement magnetic tunnel junction is used to store a first type of storage data, and the first storage requirement magnetic tunnel junction is used to store a second type of storage data. The accuracy of the first type of storage data is greater than the accuracy of the second type of storage data.

3. The writing circuit according to claim 1, characterized in that: The circuit further includes two first switch tubes and a plurality of second switch tubes, wherein the two first switch tubes are respectively connected to two ends of the spin-orbit moment layer, and the plurality of second switch tubes are connected to the tops of the plurality of magnetic tunnel junctions in a one-to-one correspondence; The voltage control module includes a first voltage control unit and a plurality of second voltage control units arranged in one-to-one correspondence with the plurality of magnetic tunnel junctions; The first voltage control unit is used to provide the write voltage to the spin-orbit moment layer through the first switch tube; Each of the second voltage control units is used to provide the corresponding control voltage to the corresponding magnetic tunnel junction through the corresponding second switch tube.

4. The writing circuit according to claim 1, characterized in that: The circuit further includes two first switch tubes and one second switch tube, the two first switch tubes are respectively connected to two ends of the spin-orbit moment layer, and the second switch tube is connected to the tops of the plurality of magnetic tunnel junctions; The voltage control module includes a first voltage control unit and a second voltage control unit; The first voltage control unit is used to provide the write voltage to the spin-orbit moment layer through the first switch tube; The second voltage control unit is used to provide the control voltage to the multiple magnetic tunnel junctions through the second switch tube.

5. A write array, characterized in that: The invention comprises a plurality of write circuits as claimed in any one of claims 1 to 4 arranged in a matrix.

6. A writing method, characterized in that: Applied in a Nand-type magnetic storage unit, the Nand-type magnetic storage unit comprises a spin-orbit moment layer and a plurality of magnetic tunnel junctions arranged on the spin-orbit moment layer; The writing method comprises: According to a preset storage requirement, the plurality of magnetic tunnel junctions are classified, wherein the classification structure of the plurality of magnetic tunnel junctions includes a first storage requirement magnetic tunnel junction and a second storage requirement magnetic tunnel junction; Determine a write voltage and a control voltage corresponding to the magnetic tunnel junction according to the number of the first storage requirement magnetic tunnel junctions among the plurality of magnetic tunnel junctions and the classification results of the plurality of magnetic tunnel junctions; Providing the write voltage to the spin-orbit moment layer and providing the control voltage to the corresponding magnetic tunnel junction; Under the write voltage and the corresponding control voltage, the first storage requirement magnetic tunnel junction has a first flip probability, and the second storage requirement magnetic tunnel junction has a second flip probability, wherein the first flip probability is greater than the second flip probability.

7. The writing method according to claim 6, characterized in that: Determining the write voltage of the Nand-type magnetic storage unit and the control voltages corresponding to the multiple magnetic tunnel junctions according to the number of magnetic tunnel junctions with a first storage requirement among the multiple magnetic tunnel junctions and the classification results of the multiple magnetic tunnel junctions includes: Determining the write voltage according to the number of first storage requirement magnetic tunnel junctions among the plurality of magnetic tunnel junctions; A control voltage corresponding to the magnetic tunnel junction is determined according to the write voltage and the classification result of the magnetic tunnel junction.

8. The writing method according to claim 6, characterized in that: The magnitude of the write voltage is proportional to the number of the first storage requirement magnetic tunnel junctions among the plurality of magnetic tunnel junctions; The control voltage of the first storage requirement magnetic tunnel junction is inversely proportional to the distance between the first storage requirement magnetic tunnel junction and the write voltage terminal of the Nand-type magnetic storage unit.

Images