Analog data similarity search memory device and operating method thereof

Abstract

An analog data similarity search memory device and an operating method thereof are disclosed. The disclosed analog data similarity search memory device comprises: a data storage block which stores an analog input voltage and which is connected to a first terminal of a data line; and a matching block which is connected to a second terminal of the data line, and which includes a match line for outputting an analog matching distance value corresponding to the voltage difference between the analog input voltage and an analog search voltage applied through a search line, wherein the voltage difference between the analog input voltage and the analog search voltage can be generated through the data line.

Description

Analog data similarity search memory element and its operation method

[0001] The present invention relates to a content-addressable memory (CAM), and more particularly, to an analog data similarity search memory element and a method for driving the same.

[0002] Content Addressable Memory (CAM) is a special type of computer memory used in certain high-speed search applications. It is also called associative memory or associative storage. It compares input search data to a stored data table and returns the address of the matching data. CAM is used in network devices such as routers, switches, and cache memory to speed up forwarding information base and routing table manipulation. Ternary Content-Addressable Memory (TCAM) is an extension of CAM. While CAM can store only two values ​​(0 and 1), TCAM can store three values: 0, 1, and "don't care." In addition, the TCAM is composed of a plurality of TCAM cells, and each TCAM cell is connected to a search line and a match line, and a search value input through the search line is compared with a data value stored in the cell, and a binary signal such as a match or a mismatch is output through the match line.

[0003] Meanwhile, in fields such as statistics, data mining, and machine learning, distance functions are commonly used to quantify the similarity between data sets. In particular, machine learning utilizes various distance functions, such as cosine distance, Hamming distance, and Euclidean distance, to measure the distance and similarity between data vectors.

[0004] Conventional deep learning applications emulate the Hamming distance in hardware using CAM or TCAM, performing parallel distance calculations and nearest neighbor search. However, the binary data vector-based Hamming distance calculation is difficult to apply to backpropagation, a differentiation-based neural network training method. Backpropagation calculates the gradient (differentiation) of input values ​​relative to output values ​​from the output layer and propagates it to the input layer.

[0005] That is, in the case of conventional CAM and TCAM, since binary digital data indicating only match / mismatch is output through the match line, it is difficult to measure the similarity between vectors for nearest neighbor search, and it is difficult to apply the function of the distance function using CAM or TCAM that can be applied to backpropagation, a differentiation-based neural network training method.

[0006] In addition, conventional SRAM (Static RAM)-based TCAMs require 16 MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), which increases cost and limits mass production and large-scale array fabrication due to the large cell size.

[0007] In addition, distance calculations between vectors with real values ​​are required for deep learning applications, but in the case of conventional CAM or TCAM, distance calculations between vectors with real values ​​are impossible because binary values ​​(1, 0) are stored / retrieved / output.

[0008] Although conventional analog CAMs have a limited range of real numbers to which the input analog values ​​match, only a limited range of real numbers can be compared, and the value output through the match line is a binary value that indicates whether or not an analog value exists within the range. Therefore, the Hamming distance using conventional analog CAMs cannot be differentiated because it calculates the distance between discrete vectors. Therefore, it is difficult to apply the distance output through the match line to the loss function for training a neural network. In order to use the Hamming distance calculated using conventional TCAMs in a one-shot learning algorithm, the vector of real numbers output from the neural network must be binarized, which requires an additional block, and loss due to binarization inevitably occurs.

[0009] Therefore, there is a need for research on analog input data similarity search elements that have a distance function that can measure the similarity between vectors for nearest neighbor search, reduce the area size, and can be applied to backpropagation, a neural network training method based on distance calculation between real-valued vectors.

[0010] The technical problem to be achieved by the present invention is to provide an analog input data similarity search element having a distance function capable of measuring the similarity between vectors for nearest neighbor search, reducing the area size, and providing a real output value applicable to backpropagation, which is a neural network training method based on a distance operation between real-valued vectors.

[0011] In addition, a technical problem to be achieved by the present invention is to provide an operating method of the above-described analog data similarity search memory element.

[0012] The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be understood by those skilled in the art from the description below.

[0013] According to one embodiment of the present invention, an analog data similarity search memory element may be provided, including a data storage block that stores an analog input voltage and is connected to a first terminal of a data line; and a matching block that is connected to a second terminal of the data line and includes a match line that outputs an analog matching distance value corresponding to a voltage difference between the analog input voltage and an analog search voltage applied through a search line, wherein a voltage difference between the analog input voltage and the analog search voltage is generated through the data line.

[0014] In one embodiment, the matching block may be comprised of a first transistor having a first dual gate and a second transistor having a second dual gate, and the data storage block may be comprised of a capacitor including a first terminal defined as a first terminal of the data line and a second terminal connected to ground, and a third transistor connected to the first terminal of the capacitor and supplying the analog input voltage to the capacitor. The data storage block may further include a fourth transistor connected to the first terminal of the capacitor and supplying a reference voltage to the capacitor, and outputting an off current (I) based on the reference voltage. off) may have an IV curve of a transistor constituting the matching block offset to a zero point. A first gate terminal of the first transistor and a third gate terminal of the second transistor connected to the first gate terminal may be connected to a first terminal of the capacitor to form the data line, and a second gate terminal of the first transistor and a fourth gate terminal of the second transistor may be coupled to the search line. A first drain terminal of the first transistor and a second drain terminal of the second transistor connected to the first drain terminal may form the match line and may be connected to ground. A first source terminal of the first transistor and a second source terminal of the second transistor connected to the first source terminal may be connected to a supply voltage source, and a voltage supplied from the supply voltage source may cancel out a difference between a first threshold voltage of the first transistor and a second threshold voltage of the second transistor. The first transistor may be a PMOS (P-type MOSFET) transistor, the second transistor may be an NMOS (N-type MOSFET) transistor, and the third transistor and the fourth transistor may be IGZO (InGaZnO) transistors. The analog matching distance value may increase as the difference between the analog input voltage and the analog search voltage increases, and may decrease as the difference between the analog input voltage and the analog search voltage decreases.

[0015] In another embodiment, the matching block may be composed of a first transistor and a second transistor, and the data storage block may be composed of a capacitor having a capacitance corresponding to the analog input voltage and including a first terminal defined as a first terminal of the data line and a second terminal coupled to the search line, and a third transistor connected to the first terminal of the capacitor and supplying the analog input voltage to the capacitor. The data storage block may further include a fourth transistor connected to the first terminal of the capacitor and supplying a reference voltage to the capacitor, and outputting an off current (I) based on the reference voltage. off ) may have an IV curve of a transistor constituting the matching block offset to a zero point. A first gate terminal of the first transistor and a second gate terminal of the second transistor connected to the first gate terminal are connected to a first terminal of the capacitor to form the data line, and a first drain terminal of the first transistor and a second drain terminal of the second transistor connected to the first drain terminal form the match line and may be connected to ground. A first source terminal of the first transistor and a second source terminal of the second transistor connected to the first source terminal are connected to a supply voltage source, and a voltage supplied from the supply voltage source may offset a difference between a first threshold voltage of the first transistor and a second threshold voltage of the second transistor. The first transistor may be a PMOS (P-type MOSFET) transistor, the second transistor may be an NMOS (N-type MOSFET) transistor, and the third transistor and the fourth transistor may be IGZO (InGaZnO) transistors.

[0016] In another embodiment, the matching block may include a first transistor and a second transistor, the data storage block may include a first sub-data storage block connected to the first transistor and a second sub-data storage block connected to the second transistor, the first sub-data block may include a first capacitor including a first terminal defined as a first terminal of a first data line and a second terminal coupled to the search line, and a third transistor connected to the first terminal of the first capacitor and supplying the first analog input voltage to the first capacitor, and the second sub-data block may include a second capacitor including a first terminal defined as a first terminal of a second data line and a second terminal coupled to the search line, and a fourth transistor connected to the first terminal of the second capacitor and supplying the second analog input voltage to the second capacitor. The first data storage block is connected to a first terminal of the first capacitor and further includes a fifth transistor for supplying a reference voltage to the first capacitor, and the second data storage block is connected to a first terminal of the second capacitor and further includes a sixth transistor for supplying the reference voltage to the second capacitor, and a reference analog matching distance value (I) output based on the reference voltage off) can be used to offset the IV curve of the transistors constituting the matching block from zero. The first gate terminal of the first transistor is connected to the first terminal of the first capacitor to form the first data line, the third gate terminal of the second transistor is connected to the first terminal of the second capacitor to form the second data line, and the first drain terminal of the first transistor and the second drain terminal of the second transistor connected to the first drain terminal form the match line and can be connected to ground. The first source terminal of the first transistor and the second source terminal of the second transistor connected to the first source terminal are connected to a supply voltage source, and a voltage supplied from the supply voltage source can cancel out a difference between a first threshold voltage of the first transistor and a second threshold voltage of the second transistor. The first transistor and the second transistor may be NMOS (N-type MOSFET) transistors, and the third transistor, the fourth transistor, the fifth transistor, and the sixth transistor may be IGZO (InGaZnO) transistors. The analog matching distance value may be backpropagated and used to update the analog input voltage of the data storage block.

[0017] According to another embodiment of the present invention, a semiconductor memory device comprising an array of analog data similarity search memory elements may be provided.

[0018] According to another embodiment of the present invention, there is provided an operating method of an analog data similarity search memory device, including a data storage block connected to a first terminal of a data line; and a matching block connected to a search line and a match line and connected to a second terminal of the data line, the operating method comprising: storing an analog input voltage corresponding to a real value of a corresponding feature point in the data storage block; receiving an analog search voltage through the search line; and outputting an analog matching distance value corresponding to a voltage difference between the analog input voltage and the analog search voltage through the match line, wherein a voltage difference between the analog input voltage and the analog search voltage occurs through the data line. The operating method may further include a step of performing a zero offset of an IV curve of a transistor constituting the matching block or a step of updating an analog input voltage of the data storage block by backpropagating the analog matching distance value.

[0019] According to embodiments of the present invention, in performing a matching distance operation between stored data and search data in an analog data similarity search memory element, an input value is converted into a voltage and applied to a data line (DL) and a search line (SL), thereby outputting a distance between consecutive input values ​​(voltages) in the form of a differentiable current, and a current is output through the match line (ML) by the difference between the stored data value and the search data value, thereby enabling comparison between real numbers, and the resulting value can be applied to a distance function to increase learning accuracy.

[0020] In addition, by implementing an analog data similarity search memory element using up to four transistors, the size of the element can be reduced, and the area can be minimized when implementing an array of elements, making it easy to mass-produce.

[0021] In addition, by using capacitors in the data storage block to store analog values ​​in the elements, data can be stored in a more detailed manner than before.

[0022] According to one embodiment of the present invention, a method of operating an analog data similarity search memory device having the advantages described above can be provided.

[0023] However, the effects of the present invention are not limited to the above effects, and can be expanded in various ways without departing from the technical spirit and scope of the present invention.

[0024] FIG. 1 is a drawing for explaining the operation concept of a semiconductor memory device according to one embodiment of the present invention.

[0025] FIG. 2a and FIG. 2b are circuit diagrams showing an analog data similarity search memory element according to one embodiment of the present invention, and FIG. 2c is a graph showing an output value of a matching distance according to a voltage difference between a data line and a search line of the analog data similarity search memory element of FIG. 2a and FIG. 2b.

[0026] FIG. 3 is a diagram showing a change in threshold voltage according to a voltage supplied to a search line in an analog data similarity search memory device according to one embodiment of the present invention.

[0027] FIG. 4 is an IV characteristic graph for explaining a method of offsetting the threshold voltage difference between an NMOS transistor and a PMOS transistor of an analog data similarity search memory device according to one embodiment of the present invention.

[0028] FIG. 5 is an IV characteristic graph for explaining the operating principle of a matching block of an analog data similarity search memory device according to one embodiment of the present invention.

[0029] FIG. 6a and FIG. 6b are circuit diagrams for an analog data similarity search memory element according to another embodiment of the present invention, and FIG. 6c is an IV characteristic graph of the analog data similarity search memory element of FIG. 6a and FIG. 5b.

[0030] FIG. 7 is a drawing explaining the operating principle of zero-offsetting the IV characteristic graph of an analog data similarity search memory device according to one embodiment of the present invention.

[0031] FIG. 8 is a circuit diagram of a semiconductor memory device composed of an NХM array of analog data similarity search memory elements according to one embodiment of the present invention.

[0032] FIG. 9a and FIG. 9b are flowcharts for explaining an operation method of an analog data similarity search memory device according to one embodiment of the present invention.

[0033] FIG. 10 is a circuit diagram for an analog data similarity search memory element according to another embodiment of the present invention.

[0034] FIG. 11a and FIG. 11b are IV characteristic graphs of an analog data similarity search memory element according to another embodiment of the present invention.

[0035] FIG. 12 is a circuit diagram of a semiconductor memory device composed of an NХM array of analog data similarity search memory elements according to another embodiment of the present invention.

[0036] FIG. 13a and FIG. 13b are drawings explaining the operating principle of zero-offsetting the IV characteristic graph of an analog data similarity search memory device according to one embodiment of the present invention.

[0037] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0038] The embodiments of the present invention described below are provided to more clearly explain the present invention to a person having ordinary skill in the art, and the scope of the present invention is not limited by the following embodiments, and the following embodiments can be modified in various other forms.

[0039] The terminology used herein is used to describe particular embodiments and is not intended to limit the present invention. The singular forms used herein may include the plural forms unless the context clearly dictates otherwise. In addition, the terms "comprise" and / or "comprising" used herein specify the presence of a stated feature, step, number, operation, element, element, and / or group thereof, but do not exclude the presence or addition of one or more other features, steps, numbers, operations, elements, elements, and / or groups thereof. In addition, the term "connected" used herein not only means that certain elements are directly connected, but also includes a concept that indirectly connects elements by interposing another element between them.

[0040] In addition, when it is said in this specification that a certain element is located "on" another element, this includes not only cases where a certain element is in contact with another element, but also cases where another element exists between the two elements. The term "and / or" as used in this specification includes any one of the listed items and any and all combinations of one or more of them. In addition, terms of degree such as "about", "substantially", etc. as used in this specification are used to mean a range of or close to the numerical value or degree, taking into account inherent manufacturing and material tolerances, and are used to prevent infringers from unfairly using the disclosure that mentions exact or absolute numbers provided to help the understanding of this specification.

[0041] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The sizes and thicknesses of areas or parts illustrated in the attached drawings may be somewhat exaggerated for clarity and convenience of explanation. Like reference numbers designate like components throughout the detailed description.

[0042] FIG. 1 is a drawing for explaining the operation concept of a semiconductor memory device according to one embodiment of the present invention.

[0043] Referring to Fig. 1, a processor, such as a central processing unit (CPU) or a graphic processing unit (GPU), can extract feature points expressed as real-valued vectors from training images (P1) by executing a driving program or an application program (P3). Specifically, training images may be provided as input values ​​to a convolutional neural network (CNN) model (P2), and real-valued vectors of the corresponding training images may be output as output values. N-way can be defined as a learning set consisting of integer N classes, and n-shot can be defined as the number of samples that each class has. For example, in FIG. 1, a first real number vector may be determined for a training image (☆), a second real number vector may be determined for a training image (□), a third real number vector may be determined for a training image (○), a fourth real number vector may be determined for a training image (◇), and a fifth real number vector may be determined for a training image (△). The processor may generate D-dimensional real number vectors representing feature points of the training images. The number of training images may be, without limitation, 5 or more.

[0044] Thereafter, the real number vector obtained through training can be stored and updated in a semiconductor memory device (200, 300) having M x N cells of the present invention. In the case of a conventional digital CAM or multi-CAM (multibit CAM), it is difficult to store an analog type real number vector in a cell (corresponding to an analog data similarity search memory element to be described later), so the real number vector is quantized and stored in the cell. However, in the present invention, when storing a real number vector in an array of a semiconductor memory device (200, 300), it can be programmed using a voltage corresponding to each analog value. A detailed operation description of the semiconductor memory device (200, 300) will be described later.

[0045] When the extracted real vector value corresponding to the query image is provided as a search value to a semiconductor memory device (200, 300) trained through a processor such as a CPU or GPU, the semiconductor memory device (200, 300) performs a search and outputs an image (☆) very similar to the real vector value of the query image, which is the basic role of a neuromorphic semiconductor.

[0046] However, in the case of conventional CAMs, the distance value for judging similarity is output as a binary value, so it is difficult to apply it to training a CNN that performs feature extraction. The semiconductor memory device (200, 300) composed of an array of analog data similarity search memory elements (10, 10', 20, 20', 30) according to the present invention receives an analog input value and outputs an analog distance value (current), so it can be applied to the error function of the CNN and used for CNN training.

[0047] FIG. 2a and FIG. 2b are circuit diagrams for an analog data similarity search memory element (10, 10') according to one embodiment of the present invention, and FIG. 2c is a graph showing an output value of a matching distance according to a voltage difference between a data line and a search line of the analog data similarity search memory element (10, 10') of FIG. 2a and FIG. 2b.

[0048] Referring to Fig. 2a, the analog data similarity search memory element (10) may be composed of a matching block (11) and a data storage block (12). When performing a matching distance operation between data stored in the data storage block (12) and search data input through the matching block (11), the analog data similarity search memory element (10) may output the distance between consecutive input data (or voltage) in the form of a differentiable current.

[0049] Specifically, the analog data similarity search memory element (10) is an analog input voltage (V D_P ) and a data storage block (12) connected to the first terminal of the data line (DL) and connected to the second terminal of the data line (DL), and an analog search voltage (V SL ) and the search line (SL) receiving the analog input voltage (V D_P ) and analog search voltage (V SL ) voltage difference (V) D_P - V SL ) may include a matching block (11) including a match line (ML) that outputs an analog matching distance value corresponding to the analog input voltage (V D_P ) may be a voltage corresponding to a value of one of the real vectors representing the feature points of the aforementioned training image. Analog search voltage (V SL ) may be a voltage corresponding to a value of one of the real vectors representing the feature points of the query image.

[0050] Analog input voltage (V) via data line (DL)D_P ) and analog search voltage (V SL ) voltage difference (V) D_P - V SL ) may occur. Here, the analog input voltage (V D_P ) is the analog search voltage (V SL ) is a voltage corresponding to a real value of one of the real vectors of the training image obtained through the training process of Fig. 1 before being input, and can be stored in the capacitor (C1) described later. Afterwards, an analog search voltage (V) is input through the search line (SL). SL ) is entered, the voltage difference (V) on the data line (DL) D_P - V SL ) occurs. Specifically, the matching block (11) may be composed of a first transistor (TR1) having a first dual gate (G1, G2) and a second transistor (TR2) having a second dual gate (G3, G4). In addition, the data storage block (12) may be configured to receive an analog input voltage (V D_P ) and a capacitor (C1) including a first terminal (T1) defined as the first terminal of the data line (DL1) and a second terminal (T2) connected to the ground, and connected to the first terminal (T1) of the capacitor (C1) and an analog input voltage (V) applied to the capacitor (C1) D_P ) is connected to the first terminal of the third transistor (TR3) and the capacitor (C1) that supplies the reference voltage, and may include a fourth transistor (TR4) that supplies the reference voltage to the capacitor (C1). The off current (I) output based on the reference voltage, which will be described later in FIG. 7 off ) can be used to offset the IV curve of the transistors constituting the matching block (11) to zero. The off current (I off ) sets the voltage stored in the capacitor (C1) to a reference voltage of 0 V, and then the analog search voltage (V SL ) is 0 V, the flowing drain current (I D )am.

[0051] In addition, the first gate terminal (G1) of the first transistor (TR1) of the matching block (11) and the third gate terminal (G3) of the second transistor (TR2) connected to the first gate terminal (G1) may be connected to the first terminal (T1) of the capacitor (C1) to form a data line (DL). The second gate terminal (G2) of the first transistor (TR1) and the fourth gate terminal (G4) of the second transistor (TR2) may be connected to a search line (SL). The first drain terminal (D1) of the first transistor (TR1) and the second drain terminal (D2) of the second transistor (TR2) connected to the first drain terminal (D1) may form a match line (ML), which may be connected to the second terminal (T2) of the capacitor (C1) or ground. And the second source terminal (S2) of the second transistor (TR2), which is connected to the first source terminal (S1) and the first source terminal (S2) of the first transistor (TR1), can be connected to a supply voltage source. The second gate terminal (G2) of the first transistor (TR1) and the fourth gate terminal (G4) of the second transistor (TR2) correspond to back gates, and the first gate terminal (G1) of the first transistor (TR1) and the third gate terminal (G3) of the second transistor (TR2) correspond to top gates. Alternatively, the second gate terminal (G2) and the fourth gate terminal (G4) can be top gates, and the first gate terminal (G1) and the third gate terminal (G3) can be back gates.

[0052] The above supply voltage source is the supply voltage (V dd ) Referring to FIG. 4, which will be described later, the first threshold voltage (V) of the first transistor (TR1) th-pmos ) and the second threshold voltage (V) of the second transistor (TR2) th-nmos ) can be the voltage difference. The first threshold voltage (V) of the first transistor (TR1) th-pmos ) and the second threshold voltage (V) of the second transistor (TR2)th-nmos ) is the voltage supplied to the source terminals of the first transistor (TR1) and the second transistor (TR2), and is the first threshold voltage (V) of the first transistor (TR1). th-pmos ) and the second threshold voltage (V) of the second transistor (TR2) th-nmos ) can be offset to produce a symmetrical IV characteristic graph. Without limitation, the first transistor (TR1) may be a PMOS (P-type MOSFET) transistor, the second transistor (TR2) may be an NMOS (N-type MOSFET) transistor, and the third transistor (TR3) and the fourth transistor (TR4) may be IGZO (InGaZnO) transistors. In addition, the analog matching distance value output through the match line (ML) may be a voltage difference (V D_P - V SL ) corresponding to the current (I D ), as a voltage difference (V D_P - V SL ) is larger, the current (I D ) increases, and the voltage difference (V D_P - V SL ) is smaller, the current (I D ) becomes smaller.

[0053] One of the important roles of the data storage block (12) is to store the desired voltage value in the capacitor (C1) for a long time, and to store the desired V in all unit cells in the array, for example, the analog data similarity search memory element (10), until searching is performed. cap (=V D_P ) value is maintained. Also, V is applied to the capacitor (C1) as the desired voltage value. cap (=V D_P ) is stored accurately without a separate write / verify process. The voltage value stored in the capacitor (C1) is V cap (=V D_P) to be maintained for a long time, since V=Q / C, the capacitance must be increased or the charge loss must be reduced. In the former case, since there is a limit to increasing the plate area of ​​the capacitor (C1), the overall charge loss must be reduced. For this purpose, it is desirable to use an IGZO-based transistor with low leakage current. Since the IGZO transistor has a leakage current that is 3 to 6 orders lower than that of a general transistor, it can guarantee a long retention time of the stored voltage.

[0054] Since it is not easy to program general resistor-based memory devices with exact values, a verification process must be performed for each write. As the number of programming steps increases, the time required increases exponentially, so it is necessary to minimize the write / verify process. Therefore, to achieve this, the desired voltage (V) must be applied to the capacitor (C1) connected to the data line (DL). D_P ) is applied and the transistor (TR3) connected to the capacitor (C1) is turned on for a sufficient time, so that the capacitor (C1) receives the desired DL value (V cap = V D_P ) can be saved.

[0055] In the case of Fig. 2a, the first terminal (T1) of the capacitor (C1) is grounded through the fourth transistor (TR4) of the data storage block (12), and the analog input voltage (V) is applied through the third transistor (TR3). D_P) in a capacitor (C1), the analog data similarity search memory element (10) of Fig. 2a can be utilized in a structure in which the voltage application cannot be quickly and flexibly changed. Optionally, in a structure in which the voltage application can be quickly changed, as in Fig. 2b, only the third transistor (TR3) is used to apply the analog input voltage (V) to the drain terminal of the third transistor (TR3). D_P ) can also be grounded to provide power.

[0056] In addition, when a zero offset is not required for the IV curve of the transistor constituting the matching block (11) as in FIG. 7, which will be described later, the data storage block (12) may not include the fourth transistor (TR4) as in FIG. 2b. A detailed description of FIG. 2b may refer to the description of FIG. 2a, excluding the fourth transistor (TR4) of the data storage block (12), unless otherwise contradictory.

[0057] Referring again to Figures 2a and 2b, an analog input voltage (V) corresponding to data is applied to store information in a capacitor ((C1) connected to a data line (DL). D_P ) can be supplied. At this time, the second terminal (T2) of the capacitor (C1) is fixed to ground and the first terminal (T1) of the capacitor (C1) is supplied with an analog input voltage (V D_P ) is charged, so V cap = V D_P Become, V cap The voltage can be supplied as the gate voltage of the first transistor (TR1) and the second transistor (TR2) of the matching block (11). Here, the search line (SL) is connected to the back gate (BG) of the first transistor (TR1) and the second transistor (TR2) constituting the matching block (11), and, as in the graph of Fig. 3, the source voltage (V) of the first transistor (TR1) or / and the second transistor (TR2) SB ) and back gate voltage (VG ) the threshold voltage of the first transistor (TR1) and the second transistor (TR2) may decrease or increase depending on the voltage difference between the source voltage (V SB ) is grounded, the search voltage applied through the search line (SL), i.e., the back gate voltage (V G ) the IV curve moves as shown in Fig. 2c. Therefore, when the voltages supplied to the search line (SL) and the data line (DL) match, a matching state is achieved, and when the search line (SL) is higher than the voltage of the data line (DL), a current (I) flows through the first transistor (TR1). D ) flows, and conversely, when the search line (SL) is lower than the voltage of the data line (DL), current (I) flows through the second transistor (TR2). D ) flows, and the flowing current (I D ) can be used to determine the degree of mismatch.

[0058] FIG. 2c is a graph showing the output value of the matching distance according to the voltage difference between the data line and the search line of the analog data similarity search memory element (10) according to one embodiment of the present invention.

[0059] Referring to FIG. 2c, the analog data similarity search memory element (10) is based on a total of six threshold voltages, and any one of 0 V, 0.2 V, 0.4 V, 0.6 V, 0.8 V, and 1.0 V is used as the analog input voltage (V D_P ) can be stored in the capacitor (C1). One of 0V, 0.2V, 0.4V, 0.6V, 0.8V, and 1.0V is selected as the analog search voltage (V) through the search line (SL). SL ) can be provided.

[0060] An analog search voltage (V) supplied to at least one of the second gate terminal (G2) of the first transistor (TR1) and the fourth gate terminal (G4) of the second transistor (TR2), which is defined as the back gate (BG) SL ) and the analog input voltage (V) formed on the data line (DL) D_P ) depending on the matching distance or drain current (I D ) shows the output. For example, a voltage of 0.6 V is applied through the search line (SL), and the analog input voltage (V) supplied to the data line (DL) D_P ) is 0.8 V, the drain current (I ) corresponding to a voltage difference of 0.2 V (0.8 V - 0.6 V) D ) flows to the match line (ML) through the drain terminal (D2) of the second transistor (TR2), which is an NMOS transistor. Conversely, a voltage of 0.6 V is applied through the search line (SL), and the analog input voltage (V ) formed on the data line (DL) D_P ) is 0.4 V, the drain current (I ) corresponding to the voltage difference - 0.2 V (0.4 V - 0.6 V) D ) flows to the match line (ML) through the drain terminal (D1) of the first transistor (TR1), which is a PMOS transistor. That is, V D_P > V SL When the gate voltage becomes positive, drain current is generated in the NMOS transistor, and V D_P < V SL In this case, the gate voltage becomes negative, which can generate drain current in the PMOS transistor.

[0061] The basic operating principle of the analog data similarity search memory element (10) as shown in Fig. 3 described later is to change the body bias of the transistors (TR1, TR2) to the reverse gate voltage (V BG ) to adjust the threshold voltage (V th ) and change the voltage (V) of the capacitor (C1) cap ) of the transistor's gate (VG ) is applied to the drain current (I) of the transistor (TR1 or TR2) by the voltage difference. D ) will flow. V cap = V gs > V th In this case, the NMOS transistor (TR2) operates and current flows, and V cap = V gs < V th When the PMOS transistor (TR1) is turned on, current flows. The threshold voltage (V th ) and V gs As the difference is small, i.e., as much as the matching degree, the voltage (V) supplied to the source terminal of the transistor (TR1 or TR2) dd ) causes less current to flow from ML.

[0062] Figure 3 illustrates a voltage (V) supplied to the reverse bias in an analog data similarity search memory element according to one embodiment of the present invention. SB ) is a diagram showing the change in threshold voltage.

[0063] Referring to Figure 3, the nmos transistor (TR2) is negatively reverse biased (+V SB ) increases, the threshold voltage (V T ) is increasing, and the positive reverse bias (-V SB ) increases, the threshold voltage (V T ) becomes smaller. Conversely, the pmos transistor (TR1) is negatively reverse biased (+V SB ) increases, the threshold voltage (V T ) is smaller, and the positive reverse bias (-V SB ) increases, the threshold voltage (V T ) can grow.

[0064] As mentioned above, if the characteristics of the pmos transistor (TR1) and nmos transistor (TR2) are ideal, the IV characteristic graph shown in Fig. 2c shows the voltage (V) of the data line (DL) G or V D_P or Vcap ) and the voltage (V) of the search line (SL) SL ) match, the current (I) flowing through the matching line (ML) D ) is O. However, in reality, since the characteristics of the pmos transistor (TR1) and nmos transistor (TR2) are different, the voltage (V) of the data line (DL) cap ) and the voltage (V) of the search line (SL) SL ) match, the off current (I) is transmitted to some extent through the matching line (ML) as in (a) of Fig. 7. off ) can flow. Therefore, the output drain current of the analog data similarity search memory element (10) is turned off as the current (I off ) needs to be offset.

[0065] FIG. 4 is an IV characteristic graph for explaining a method of offsetting the threshold voltage difference between an NMOS transistor and a PMOS transistor of an analog data similarity search memory device according to one embodiment of the present invention.

[0066] Referring to Figure 4, in the case of the PMOS transistor (TR1), the source is generally grounded (GND) and a negative voltage is supplied to the drain, so V gs = -V g Therefore, an IV characteristic graph with a threshold voltage like ① can be obtained.

[0067] In case ②, the supply voltage (V) is applied to the source of the PMOS transistor (TR1). dd ) and ground the drain (GND), the voltage (V) supplied to the source is positive compared to η. dd ) can be obtained by shifting the red IV characteristic graph. Therefore, the threshold voltage (V) of the NMOS transistor (TR2) th-nmos ) and the threshold voltage (V) of the PMOS transistor (TR1) th-pmos ) as the difference between the supply voltage (V) and the source of the PMOS transistor (TR1). dd) is applied, the IV characteristic graphs of the NMOS transistor (TR2) and PMOS transistor (TR1) appear in a symmetrical manner.

[0068] In addition, in order for the PMOS transistor (TR1) and the NMOS transistor (TR2) to obtain symmetrical IV characteristic graphs, it is necessary to design the channel width of the PMOS transistor (TR1), which uses holes with low mobility as carriers, to be larger than that of the NMOS transistor (TR2).

[0069] FIG. 5 is an IV characteristic graph for explaining the operating principle of a matching block of an analog data similarity search memory device according to one embodiment of the present invention.

[0070] Referring to Fig. 5, if three pieces of information, -1, 0, and 1, are provided to the data line (DL) and the search line (SL), without limitation, the drain current (I) corresponding to the matching distance D ) flows. There is a negative back bias, i.e. a positive V on the search line (SL). SB If SL = 1, then the search line (SL) is negative -V. SB When SL = -1 is applied, it is assumed that SL = -1. Here, at the point where the IV characteristic graphs of the pmos transistor (TR1) and nmos transistor (TR2) intersect (DL(-1), DL(0), DL(1)) at each SL(-1), SL(0), SL(1), the drain current (I D ) can be 0. In this case, if DL(-1, 0, 1) and SL(-1, 0, 1) match, the drain current (I D) can be O. If SL(1) and DL(O), some current will flow through the pmos transistor (TR1), and if DL(-1), twice the current of DL(O) will flow. Conversely, if SL(-1) and DL(1), the most current will flow through the nmos transistor (TR2). Finally, if SL(0) and DL(1), the pmos transistor (TR1) is off and only the nmos transistor (TR2) is on, and conversely, if DL(-1), the pmos transistor (TR1) is on and the nmos transistor (TR2) is off. Ultimately, if the distance for determining similarity matches, the same current will flow through each different transistor. If an FD-SOI device is used instead of a conventional bulk CMOS transistor, a lower leakage current and threshold voltage (V) due to reverse bias can be achieved. t ) allows for a wider range of changes, enabling the production of devices that can be applied to a wider range of situations.

[0071] In another embodiment, the positions of the drain terminal (D1) and the source terminal (S1) of the first transistor (TR1) in FIGS. 2a and 2b are changed so that the drain terminal (D1) is connected to the supply voltage source (V dd ) and the source terminal (S1) can be connected to the match line (ML). Similarly, the positions of the drain terminal (D2) and the source terminal (S2) of the second transistor (TR2) are changed so that the drain terminal (D2) is connected to the supply voltage source (V dd ) and the source terminal (S2) can be connected to the match line (ML).

[0072] As described above, the analog data similarity search memory element (10) is comprised of fewer elements compared to a conventional 16T CMOS TCAM, thereby reducing the overall area. In addition, a differentiable analog output value (current) is generated through distance calculation between consecutive real numbers (voltages).

[0073] In FIG. 2a and FIG. 2b, the search line (SL) and the back gate (BG) of the first transistor (TR1) and the second transistor (TR2) having a dual gate structure are connected, and the analog search voltage (V) supplied through the back gate (BG) SL ) and data line (DL) are provided with analog input voltage (V D_P ) depending on the voltage difference between them, the drain current (I D ) is output, but as shown in FIG. 6a and FIG. 6b to be described later, the second terminal (T2) of the capacitor (C1) is connected to the search line (SL), and the analog input voltage (V) supplied to the first terminal (T1) of the capacitor (C1) D_P ) and the analog search voltage (V) supplied to the second terminal (T2) of the capacitor (C1). SL ) can be transmitted to the gate terminals of the first transistor (TR1) and the second transistor (TR2) having a single-gate structure.

[0074] FIG. 6a and FIG. 6b are circuit diagrams for an analog data similarity search memory element (20, 20') according to another embodiment of the present invention, and FIG. 6c is an IV characteristic graph of the analog data similarity search memory element (20, 20') of FIG. 6a and FIG. 6b.

[0075] Referring to FIG. 6a, the analog data similarity search memory element (20) may be composed of a matching block (21) including a first transistor (TR1) and a second transistor (TR2) having a single gate structure, and a data storage block (22) including a third transistor (TR3), a fourth transistor (TR4), and a capacitor (C1).

[0076] The first gate terminal (G1) of the first transistor (TR1) of the matching block (21) and the second gate terminal (G2) of the second transistor (TR2) connected to the first gate terminal (G1) may be connected to the first terminal (T1) of the capacitor (C1) to form a data line (DL). The first drain terminal (D1) of the first transistor (TR1) and the second drain terminal (D2) of the second transistor (TR2) connected to the first drain terminal (D1) may form a match line (ML) and may be connected to the ground. In addition, the first source terminal (S1) of the first transistor (TR1) and the second source terminal (S2) of the second transistor (TR2) connected to the first source terminal (S2) may be connected to a supply voltage source (V dd ) can be connected. In addition, the data storage block (22) can be connected to an analog input voltage (V D_P ) and a capacitor (C1) including a first terminal (T1) defined as a first terminal of a data line (DL) and a second terminal (T2) coupled to a search line (SL), and connected to the first terminal (T1) of the capacitor (C1) and an analog input voltage (V) applied to the capacitor (C1) D_P ) is connected to the first terminal of the third transistor (TR3) and the capacitor (C1), and may include a fourth transistor (TR4) that supplies a reference voltage to the capacitor (C1).

[0077] Except that the first transistor (TR1) and the second transistor (TR2) in FIG. 6a have a single-gate structure and the search line (SL) is coupled to the second terminal (T2) of the capacitor (C1), the matching block (21) and the data storage block (22) are similar in configuration to the matching block (11) and the data storage block (12) of FIG. 2a, so that a detailed description of the matching block (21) and the data storage block (22) may refer to the detailed description of the matching block (11) and the data storage block (12) of FIG. 2a, unless otherwise contradictory.

[0078] Meanwhile, in Fig. 2a, the analog search voltage (V) supplied through the back gate (BG) of the transistor (TR1, TR2) SL ) and the analog input voltage (V) of the capacitor (C1) supplied through the top gate connected to the data line (DL). D_P ) depending on the voltage difference between them, the drain current (I D ) is output, whereas in Fig. 6a, the first transistor (TR1) and the second transistor (TR2) have a single-gate structure, and the search line (SL) is coupled to the second terminal (T2) of the capacitor (C1), so that the analog input voltage (V) supplied to the first terminal (T1) of the capacitor (C1) D_P ) and the analog search voltage (V) supplied to the second terminal (T2) of the capacitor (C1). SL ) depending on the voltage difference between them, the drain current (I D ) and Fig. 6a has a difference from the method of generating the voltage difference of Fig. 2a.

[0079] The analog data similarity search memory element (20') of FIG. 6b may, like FIG. 2b, omit the fourth transistor (TR4) constituting the analog data similarity search memory element (20) of FIG. 6a.

[0080] FIG. 6c is an IV characteristic graph of an analog data similarity search memory element (20, 20') according to one embodiment of the present invention.

[0081] Referring to Fig. 6c, the IV characteristic graph on the right (red) is represented by the second transistor (TR2), which is an NMOS transistor, and the IV characteristic graph on the left (blue) is represented by the first transistor (TR1), which is a PMOS transistor. The x-axis represents the analog input voltage (V D-P ) and analog search voltage (V SL ) voltage difference (V) between cap = V D_P - V SL) and the y-axis represents the drain current (I) flowing to the match line (ML) through the drain terminal of the first transistor (TR1) or the second transistor (TR2) depending on the voltage difference. D ) is the voltage difference (V cap ) increases, the drain current (I D ) becomes larger and smaller, the drain current (I D ) becomes smaller. Ideally, the voltage difference (V cap = V D_P - V SL ) is 0, the drain current (I D ) can be 0.

[0082] FIG. 7 is a drawing explaining the operating principle of zero-offsetting the IV characteristic graph of an analog data similarity search memory element (20, 20') according to one embodiment of the present invention.

[0083] Referring to Figure 7, the voltage (V) of the data line (BL) D_P ) and the voltage (V) of the search line (SL) SL ) match, the off current (I) is transmitted through the matching line (ML). off ) can flow (a). When there is one analog data similarity search memory element (20, 20'), the off current (I off ) flows, but there is no problem, but each analog data similarity search memory element (10 or 20) of the semiconductor memory device (200) composed of the NХM array of the analog data similarity search memory element (10) of FIG. 8 described later has an off current (I off ) may appear differently, it may be necessary to zero-offset the IV characteristic graph of the analog data similarity search memory element (10, 20) as in (b).

[0084] In order to zero-offset the IV characteristic graph of the data similarity search memory element, the fourth transistor (TR4) of the aforementioned data storage block (12, 22) can be used. Specifically, first, the fourth transistor (TR4) is turned on so that 0 V is applied to the first terminal (T1) of the capacitor (C1). Then, the fourth transistor (TR4) is turned off so that the first terminal (T1) of the capacitor (C1) is fixed to 0 V, and then I off By subtracting the current, the IV characteristic graph of the data similarity search memory element (10, 20) can be offset to zero.

[0085] FIG. 8 is a circuit diagram of a semiconductor memory device (200) configured with an MХN array of analog data similarity search memory elements according to an embodiment of the present invention. The circuit diagram and detailed description of each analog data similarity search memory element (10) may refer to FIG. 2A and FIG. 2B described above. Referring to FIG. 8, the semiconductor memory device (200) may be configured with an NХM array of analog data similarity search memory elements (10). The N analog data similarity search memory elements (10) in the first row may store and update real vector values ​​representing feature points of a first training image. That is, the N real values ​​are defined as a vector string, and the N real values ​​are each stored in the analog data similarity search memory element (10). Similarly, the N analog data similarity search memory elements (10) in the second row may store and update real vector values ​​representing feature points of a second training image. The N analog data similarity search memory elements (10) of the Mth row can store and update real vector values ​​representing feature points of the Nth training image.

[0086] In an array environment having MХN analog data similarity search memory elements (10), data line (DL) updates are sequentially programmed row by row. When a 1ХN-dimensional real number vector extracted by completing training on a specific image in a CNN is programmed in the first row, each V D_P The real vector value can be programmed by applying voltage. At this time, the voltage of the first column to be programmed (V G_P ) is applied, the remaining columns are not programmed. If the same voltage is applied to each search line (SL) and data line (DL), the difference in distance between the search line (SL) and the data line (DL) is 0 V, so the current value coming out through the ADC can be almost 0. If it is not zero (0), the V of the corresponding column D_P The problem can be solved by adding a write / verify process that converges to '0' while changing the value. When updating a data line (DL), sequentially program a total of m rows, read the distance, and then update the V of all columns before updating the data. G_E You can reset the data by turning it on.

[0087] In addition, the read operation is performed simultaneously in all analog data similarity search memory elements (10) in parallel. When the data storage block (12) of all analog data similarity search memory elements is updated, the real vector values ​​extracted from the 1ХN-dimensional query image are stored in each SL1 to SL n Voltage is applied simultaneously until V dd As shown in the aforementioned Fig. 4, the threshold voltage (V) of the nmos transistor and the pmos transistor th) can be set to a value equal to the difference. After the parallel read operation, the voltage difference between the data line (DL) and the search line (SL) is read in each analog data similarity search memory element (10), so that the sum of the distance values ​​(currents) output from n analog data similarity search memory elements (10) for each row is provided to the ADC. The distance values ​​output from each row can be read in a total of m ADCs, and the value with the smallest distance can be determined as the matching image. At this time, unlike conventional TCAMs, the distance can be calculated in the form of an analog value, so that the distance value can be used for backpropagation when applied to a loss function.

[0088] In Fig. 8, the analog data similarity search memory element (10) can be replaced with an analog data similarity search memory element (10', 20, 20').

[0089] FIG. 9a and FIG. 9b are flowcharts for explaining an operation method of an analog data similarity search memory device according to one embodiment of the present invention.

[0090] Referring to FIG. 9A, an operation method of an analog data similarity search memory device including a data storage block connected to a first terminal of a data line; and a matching block connected to a search line and a match line and connected to a second terminal of the data line may include a step (S900) of performing a zero offset of a transistor IV curve constituting the matching block as shown in FIG. 7; a step (S902) of storing an analog input voltage corresponding to a real value of a corresponding feature point in the data storage block; a step (S904) of receiving an analog search voltage through a search line; and a step (S908) of outputting an analog matching distance value corresponding to a voltage difference between the analog input voltage and the analog search voltage through the match line. A voltage difference between the analog input voltage and the analog search voltage may be generated through the data line. Optionally, a step of updating the analog input voltage of the data storage block by backpropagating the analog matching distance value may be further included. Since the above analog matching distance value is expressed in the form of a differentiable current that represents the distance between consecutive input data (or voltage), it is easy to utilize it for backpropagation, unlike conventional techniques.

[0091] Meanwhile, the step (S900) of performing the zero offset of the constituent transistor IV curve may be processed in parallel with other steps, and may be performed after the step (S908) of outputting the analog matching distance value through the match line, as shown in FIG. 9b. Unless otherwise contradictory, a detailed description of FIG. 9b may refer to the description of FIG. 9a.

[0092] As described above, the present invention relates to a CMOS-based similarity memory having an IV characteristic graph that mimics the implementation of the Euclidean distance function, thereby enabling parallel distance calculations between data vectors. Furthermore, since the memory performs distance calculations between data vectors composed of continuous values ​​rather than binary values, it can be utilized as a differentiable computing hardware resource, and thus can be applied in situ to the training of neural networks, thereby improving computing efficiency.

[0093] FIG. 10 is a circuit diagram for an analog data similarity search memory element (30) according to another embodiment of the present invention.

[0094] Referring to Fig. 10, the analog data similarity search memory element (30) may be composed of a matching block (31) and a data storage block (32). The analog data similarity search memory element (30) may output the distance between consecutive input data (or voltage) in the form of a differentiable current by performing a matching distance operation between data stored in the data storage block (32) and search data input through the matching block (31).

[0095] The matching block (31) may be composed of a first transistor (TR1) and a second transistor (TR2). The data storage block (32) may include a first sub-data storage block (DSB1) connected to the first transistor (TR1) and a second data storage block (DSB2) connected to the second transistor (TR2). The first sub-data block (DSB1) may receive a first analog input voltage (V D-P) and a first capacitor (C1) having a first terminal (T1) defined as a first terminal of a first data line (DL1) and a second terminal (T2) coupled to a search line (SL), and connected to the first terminal (T1) of the first capacitor (C1) and a first analog input voltage (V) applied to the first capacitor (C1) D-P ) may include a third transistor (TR3) that supplies a second analog input voltage (-V D_P ) and a second capacitor (C2) including a first terminal (T1) defined as a first terminal of a second data line (DL2) and a second terminal (T2) coupled to a search line (SL), and connected to the first terminal (T1) of the second capacitor (C2) and a second analog input voltage (-V) applied to the second capacitor (C2) D_P ) may include a fourth transistor (TR4) that supplies the signal.

[0096] Optionally, the first data storage block (DSB1) may further include a fifth transistor (TR5) connected to a first terminal (T1) of a first capacitor (C1) and supplying a reference voltage (e.g., 0V) to the first capacitor (C1). Similarly, the second data storage block (DSB2) may further include a sixth transistor (TR6) connected to a first terminal (T1) of a second capacitor (C2) and supplying the reference voltage (e.g., 0V) to the second capacitor. In the aforementioned FIG. 7, an off current (I) output based on the reference voltage off ) can be used to offset the IV curve of the transistors constituting the above matching block from zero.

[0097] In addition, the first gate terminal (G1) of the first transistor (TR1) may be connected to the first terminal (T1) of the first capacitor (C1) to form a first data line (DL1), and the second gate terminal (G2) of the second transistor (TR2) may be connected to the first terminal (T1) of the second capacitor (C2) to form a second data line (DL2). In addition, the first drain terminal (D1) of the first transistor (TR1) and the second drain terminal (D2) of the second transistor (TR2) connected to the first drain terminal (D1) may form a match line (ML) and may be connected to the ground. The first source terminal (S1) of the first transistor (TR1) and the second source terminal (S2) of the second transistor (TR2) connected to the first source terminal (S2) may be connected to a supply voltage source (V dd ) can be connected. Without limitation, the first transistor (TR1) and the second transistor (TR2) can both be NMOS (N-type MOSFET) transistors, and the third transistor (TR3), the fourth transistor (TR4), the fifth transistor (TR5), and the sixth transistor (TR6) can be IGZO (InGaZnO) transistors.

[0098] In FIGS. 6a and 6b, the matching block (21) is configured with a PMOS (P-type MOSFET) transistor and an NMOS (N-type MOSFET) transistor, but in FIG. 10, the matching block (31) is configured with two NMOS (N-type MOSFET) transistors.

[0099] As described above, the analog matching distance value output from the matching block (21, 31) can be backpropagated to update the analog input voltage stored in the data storage block (22, 32).

[0100] FIG. 11a and FIG. 11b are IV characteristic graphs of an analog data similarity search memory element (30) according to another embodiment of the present invention.

[0101] Referring to Fig. 11a, as an IV characteristic graph of the first transistor (TR1), the analog input voltage (V) stored in the data storage block (32) CAP or V D_P ) is applied through the search line (SL) coupled to the second terminal (T2) of the capacitor (C1, C2) and the analog search voltage (V SL ) is greater than V, the first transistor (TR1) operates, and the first transistor (TR1) is V CAP - V SL The drain current (I) is equal to the voltage difference D ) can be supplied as a match line (ML).

[0102] Referring to Fig. 11b, as an IV characteristic graph of the second transistor (TR2), an analog search voltage (V) applied through a search line (SL) coupled with the second terminal (T2) of the capacitor (C1, C2) SL ) is the analog input voltage (V) stored in the data storage block (22). CAP or V D_P ) is greater than V, the second transistor (TR2) operates, and the second transistor (TR2) is V SL - V CAP The drain current (I) is equal to the voltage difference D ) can be supplied as a match line (ML).

[0103] Fig. 12 is a circuit diagram of a semiconductor memory device (300) composed of an NХM array of analog data similarity search memory elements (20) according to another embodiment of the present invention. The circuit diagram and detailed description of each analog data similarity search memory element (30) may be referred to the aforementioned Fig. 10.

[0104] Referring to FIG. 12, a semiconductor memory device (300) may be configured with analog data similarity search memory elements (30) of an NХM array. The N analog data similarity search memory elements (30) of the first row may store and update real vector values ​​representing feature points of a first training image. That is, the N real values ​​are defined as a vector sequence, and the N real values ​​are each stored in the analog data similarity search memory elements (30). Similarly, the N analog data similarity search memory elements (30) of the second row may store and update real vector values ​​representing feature points of a second training image. The N analog data similarity search memory elements (30) of the M-th row may store and update real vector values ​​representing feature points of an N-th training image. Word lines (WL0 to WL m ) is connected to the transistors (TR3, TR4) of the data storage block (22) of the analog data similarity search memory element (20), so that an analog input voltage corresponding to a feature point of a training image can be applied to the data storage block (32). Bit lines (BL0 to BL n ) is connected to a search line (SL) coupled with a second terminal (T2) of a capacitor (C1, C2), so that an analog search voltage is applied to the second terminal (T2) of the capacitor (C1, C2).

[0105] FIG. 13a and FIG. 13b are drawings explaining the operating principle of zero-offsetting the IV characteristic graph of an analog data similarity search memory device according to one embodiment of the present invention.

[0106] Referring to Fig. 13a, depending on the device characteristics, the first transistor (TR1) and the second transistor (TR2) have a negative threshold voltage (V TH ) can have. At this time, as mentioned above in Fig. 7, the off current (I) is applied to the analog data similarity search memory element (20). off) may occur, and a positive off current (I off ) may appear.

[0107] Referring to Fig. 13b, depending on the characteristics of the element (30), the first transistor (TR1) and the second transistor (TR2) have a positive threshold voltage (V TH ) can have. At this time, as mentioned above in Fig. 7, the off current (I) is applied to the analog data similarity search memory element (30). off ) may occur, and negative off current (I off ) may appear. Off current (I off ) is the drain current (I) that flows when a reference voltage (0 V) is applied to the capacitors (C1, C2) of the data storage block (22) and then 0 V is applied to the transistors (TR1, TR2) of the match block (ML). D ) is the value.

[0108] In an environment that takes into account the zero offset of the IV characteristic graph of the analog data similarity search memory element (30), the matching distance of the semiconductor memory device (300) composed of the NХM array of the analog data similarity search memory element (30) of FIG. 12 can be expressed as in [Mathematical Formula 1] below.

[0109] [Mathematical Formula 1]

[0110]

[0111] Here, I sum(WLn) The drain current (I) output from N analog data similarity search memory elements (20) connected to the word line (WLn) D ) is the sum of, and I off is the off current determined based on the reference voltage, Vcap is the analog input voltage stored in the capacitors (C1, C2) of the data storage block (22), and V SL is the analog search voltage applied through the search line (SL), and V this the threshold voltage of the transistor, and K is a constant value.

[0112] In this specification, preferred embodiments of the present invention have been disclosed, and although specific terms have been used, they have been used in a general sense only to easily explain the technical contents of the present invention and to help the understanding of the invention, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of ​​the present invention can be implemented in addition to the embodiments disclosed herein. Those skilled in the art will appreciate that the analog data similarity search memory element and the operating method thereof, and the semiconductor memory device comprising an array of analog data similarity search memory elements in the embodiments described with reference to FIGS. 1 to 13b can be variously substituted, changed, and modified without departing from the technical idea of ​​the present invention. As a specific example, in the above-described embodiments, the transistors of the matching block (11) are PMOS and NMOS transistors and the transistors of the data storage device (12) include IGZO transistors. However, instead of PMOS and NMOS transistors, ferroelectric transistors may be used, and instead of IGZO transistors, resistive RAM (RRAM) or phase change RAM (PRA) may be used. Therefore, the scope of the invention should not be defined by the described embodiments, but should be defined by the technical ideas described in the claims.

[0113] [Explanation of symbols]

[0114] 10, 20, 30: Analog data similarity search memory element

[0115] 11, 21, 31: Matching blocks

[0116] 12, 22, 32: Data storage blocks

[0117] 200, 300: Semiconductor memory devices

[0118] The present invention relates to an analog data similarity search memory device and an operating method thereof, and has industrial applicability.

Claims

1. A data storage block that stores an analog input voltage and is connected to the first terminal of the data line; and A matching block is connected to the second terminal of the data line and includes a match line that outputs an analog matching distance value corresponding to the voltage difference between the analog input voltage and the analog search voltage applied through the search line. An analog data similarity search memory element in which a voltage difference between the analog input voltage and the analog search voltage occurs through the data line.

2. In paragraph 1, The above matching block is composed of a first transistor having a first dual gate and a second transistor having a second dual gate, An analog data similarity search memory element, wherein the data storage block comprises a capacitor having a first terminal defined as a first terminal of the data line and a second terminal connected to ground, and a third transistor connected to the first terminal of the capacitor and supplying the analog input voltage to the capacitor.

3. In paragraph 2, The above data storage block is further comprising a fourth transistor connected to the first terminal of the capacitor and supplying a reference voltage to the capacitor; Off current (I) output based on the above reference voltage off ) An analog data similarity search memory element in which the IV curves of the transistors constituting the above matching block are zero-offset.

4. In paragraph 2, The first gate terminal of the first transistor and the third gate terminal of the second transistor connected to the first gate terminal are connected to the first terminal of the capacitor to form the data line, An analog data similarity search memory element in which the second gate terminal of the first transistor and the fourth gate terminal of the second transistor are connected to the search line.

5. In paragraph 2, An analog data similarity search memory element in which a first drain terminal of the first transistor and a second drain terminal of the second transistor connected to the first drain terminal form the match line and are connected to ground.

6. In paragraph 2, The first source terminal of the first transistor and the second source terminal of the second transistor connected to the first source terminal are connected to a supply voltage source, An analog data similarity search memory element in which the voltage supplied from the supply voltage source cancels out the difference between the first threshold voltage of the first transistor and the second threshold voltage of the second transistor.

7. In paragraph 2 or 3, An analog data similarity search memory element in which the first transistor is a PMOS (P-type MOSFET) transistor, the second transistor is an NMOS (N-type MOSFET) transistor, and the third transistor and the fourth transistor are IGZO (InGaZnO) transistors.

8. In paragraph 1, An analog data similarity search memory element in which the analog matching distance value increases as the difference between the analog input voltage and the analog search voltage increases, and decreases as the difference between the analog input voltage and the analog search voltage decreases.

9. In paragraph 1, The above matching block is composed of a first transistor and a second transistor, An analog data similarity search memory element, wherein the data storage block comprises a capacitor having a capacitance corresponding to the analog input voltage and including a first terminal defined as a first terminal of the data line and a second terminal coupled to the search line, and a third transistor connected to the first terminal of the capacitor and supplying the analog input voltage to the capacitor.

10. In paragraph 9, The above data storage block is further comprising a fourth transistor connected to the first terminal of the capacitor and supplying a reference voltage to the capacitor; Off current (I) output based on the above reference voltage off ) according to which the IV curve of the transistor constituting the above matching block is an analog data similarity search memory element with a zero offset.

11. In paragraph 9, The first gate terminal of the first transistor and the second gate terminal of the second transistor connected to the first gate terminal are connected to the first terminal of the capacitor to form the data line, An analog data similarity search memory element in which a first drain terminal of the first transistor and a second drain terminal of the second transistor connected to the first drain terminal form the match line and are connected to ground.

12. In paragraph 9, The first source terminal of the first transistor and the second source terminal of the second transistor connected to the first source terminal are connected to a supply voltage source, An analog data similarity search memory element in which the voltage supplied from the supply voltage source cancels out the difference between the first threshold voltage of the first transistor and the second threshold voltage of the second transistor.

13. In paragraph 9 or 10, An analog data similarity search memory element in which the first transistor is a PMOS (P-type MOSFET) transistor, the second transistor is an NMOS (N-type MOSFET) transistor, and the third transistor and the fourth transistor are IGZO (InGaZnO) transistors.

14. In paragraph 1, The above matching block is composed of a first transistor and a second transistor, The data storage block includes a first sub-data storage block connected to the first transistor and a second sub-data storage block connected to the second transistor, The first sub-data block includes a first capacitor having a first terminal defined as a first terminal of a first data line and a second terminal coupled to the search line, and a third transistor connected to the first terminal of the first capacitor and supplying the first analog input voltage to the first capacitor, An analog data similarity search memory element, wherein the second sub-data block comprises a second capacitor including a first terminal defined as a first terminal of a second data line and a second terminal coupled to the search line, and a fourth transistor connected to the first terminal of the second capacitor and supplying the second analog input voltage to the second capacitor.

15. In paragraph 14, The first data storage block is connected to the first terminal of the first capacitor and further includes a fifth transistor for supplying a reference voltage to the first capacitor, The second data storage block is connected to the first terminal of the second capacitor and further includes a sixth transistor for supplying the reference voltage to the second capacitor, The reference analog matching distance value (I) output based on the above reference voltage off ) An analog data similarity search memory element in which the IV curves of the transistors constituting the above matching block are zero-offset.

16. In paragraph 14, The first gate terminal of the first transistor is connected to the first terminal of the first capacitor to form the first data line, and the third gate terminal of the second transistor is connected to the first terminal of the second capacitor to form the second data line. An analog data similarity search memory element in which a first drain terminal of the first transistor and a second drain terminal of the second transistor connected to the first drain terminal form the match line and are connected to ground.

17. In paragraph 14, The first source terminal of the first transistor and the second source terminal of the second transistor connected to the first source terminal are connected to a supply voltage source, An analog data similarity search memory element in which the voltage supplied from the supply voltage source cancels out the difference between the first threshold voltage of the first transistor and the second threshold voltage of the second transistor.

18. In paragraph 14 or 15, An analog data similarity search memory element wherein the first transistor and the second transistor are NMOS (N-type MOSFET) transistors, and the third transistor, the fourth transistor, the fifth transistor, and the sixth transistor are IGZO (InGaZnO) transistors.

19. In paragraph 1, An analog data similarity search memory element in which the above analog matching distance value is backpropagated and used to update the analog input voltage of the data storage block.

20. A semiconductor memory device comprising an array of analog data similarity search memory elements as described in claim 1.

21. A method of operating an analog data similarity search memory device, comprising: a data storage block connected to a first terminal of a data line; and a matching block connected to a search line and a match line and connected to a second terminal of the data line; A step of storing an analog input voltage corresponding to a real value of the corresponding feature point in the above data storage block; A step of receiving an analog search voltage through a search line; and A step of outputting an analog matching distance value corresponding to a voltage difference between the analog input voltage and the analog search voltage through a match line, An operating method of an analog data similarity search memory element in which a voltage difference between the analog input voltage and the analog search voltage occurs through the data line.

22. In paragraph 21, An operating method of an analog data similarity search memory device further comprising a step of performing a zero offset of a transistor IV curve constituting the above matching block.

23. In paragraph 21, An operating method of an analog data similarity search memory device, further comprising a step of updating an analog input voltage of the data storage block by backpropagating the analog matching distance value.

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