360 degree magnetic angle sensor

Abstract

The present invention provides a 360-degree magnetic angle sensor, which includes: an anisotropic magnetoresistive sensor, which generates a first signal representing a magnetic angle based on a magnetic field in a sensing plane, and the first signal has an angular range of 180 degrees; a Hall sensor, which generates a second signal representing a magnetic angle based on a magnetic field in the sensing plane, and the second signal has an angular range of 360 degrees; a signal processing circuit, which is electrically connected to the anisotropic magnetoresistive sensor and the Hall sensor, and which determines the interval to which the magnetic angle belongs based on the second signal, and the interval to which the magnetic angle belongs is 0 to 180 degrees or 180 to 360 degrees, and generates a third signal representing the magnetic angle in combination with the interval to which the magnetic angle belongs and the first signal, and the third signal has an angular range of 360 degrees. Compared with the prior art, the present invention can not only realize high-precision angle measurement within a 360-degree range, but also reduce volume and cost.

Description

[Technical field]

[0001] The present invention relates to the field of magnetic field sensors, and in particular to a sensor for measuring angles through a magnetic field. [Background technology]

[0002] At present, anisotropic magnetoresistance (AMR) technology is widely used in magnetic field sensors, and the manufacturing process is also mature. The resistance value of AMR depends on the angle between the current and the magnetization direction. In the measurement of magnetic angle, a double Wheatstone bridge mode is adopted, in which one bridge outputs a sine signal and the other outputs a cosine signal. The specific angle value can be obtained by the inverse tangent. For the AMR angle sensor, its magnetic layer always works in a magnetization saturation state. In this state, it can be considered that the direction of the externally applied magnetic field is basically consistent with the magnetization direction of the magnetic resistance strip. Since the output of the AMR angle sensor changes with the magnetic field angle as the relationship between sin2θ and cos2θ, the angle period that AMR can measure is only 180 degrees, and the scope of application is also greatly limited.

[0003] There are many 360-degree magnetic angle sensors based on other principles, such as the Hall effect, giant magnetoresistance (GMR) effect, and tunnel magnetoresistance (TMR) effect. The accuracy of the angle sensor based on the Hall effect is lower than that of the AMR due to the signal-to-noise ratio of the Hall effect itself. The accuracy of the angle sensor based on the giant magnetoresistance (GMR) effect and the tunnel magnetoresistance (TMR) effect is higher than that of the Hall effect, but lower than that of the AMR. The reason is that for the AMR angle sensor, there is only one magnetic layer, and its accuracy error mainly comes from the influence of the shape anisotropy field and magnetocrystalline anisotropy field of the layer. For GMR and TMR, the core structure contains two magnetic layers, namely the free layer and the pinned layer, and their resistance depends on the angle between the magnetization directions of the free layer and the pinned layer. In addition to the shape anisotropy field and magnetocrystalline anisotropy field in the free layer, the error source also includes that under the action of the external magnetic field, the free layer changes with the external magnetic field by θ1, and the magnetization direction of the pinned layer also changes by a small angle θ2, and this θ2 error will be superimposed on the original error. In addition, the static magnetointeraction between the free layer and the pinned layer will also affect the accuracy. These factors combined will reduce the final accuracy of the sensor.

[0004] Therefore, it is necessary to propose a technical solution to overcome the above problems. [Summary of the invention]

[0005] One of the purposes of the present invention is to provide a 360-degree magnetic angle sensor, which can not only achieve high-precision angle measurement within a 360-degree range, but also reduce volume and cost.

[0006] According to one aspect of the present invention, the present invention provides a 360-degree magnetic angle sensor, which includes: an anisotropic magnetoresistive sensor, which generates a first signal representing a magnetic angle based on a magnetic field in a sensing plane, and the first signal has an angular range of 180 degrees; a Hall sensor, which generates a second signal representing a magnetic angle based on the magnetic field in the sensing plane, and the second signal has an angular range of 360 degrees; a signal processing circuit, which is electrically connected to the anisotropic magnetoresistive sensor and the Hall sensor, and which determines the interval of the magnetic angle based on the second signal, and the interval is 0 to 180 degrees or 180 to 360 degrees, and generates a third signal representing the magnetic angle in combination with the interval of the magnetic angle and the first signal, and the third signal has an angular range of 360 degrees.

[0007] Furthermore, the anisotropic magnetoresistive sensor, the Hall sensor and the signal processing circuit are integrated into a single chip.

[0008] Furthermore, the single chip includes a substrate, and a first structure layer and a second structure layer stacked on the substrate, the Hall sensor and the signal processing circuit are arranged in the first structure layer; the anisotropic magnetoresistive sensor is arranged in the second structure layer.

[0009] Furthermore, the first structural layer is located on the substrate; and the second structural layer is located above the first structural layer.

[0010] Furthermore, the single chip also includes an isolation layer and a third structural layer, the isolation layer is located between the first structural layer and the second structural layer, and via metal passes through the isolation layer to electrically connect the anisotropic magnetoresistance sensor and the signal processing circuit; the third structural layer is located above the second structural layer, and the third structural layer includes an anisotropic magnetoresistance sensor protection layer and electrodes thereon, and the electrodes are connected to the signal processing circuit through via metal.

[0011] Furthermore, the substrate 101 is made of single crystal silicon in a standard CMOS process; the Hall sensor and the dedicated integrated circuit in the second structural layer are manufactured on a single crystal silicon substrate using a standard CMOS process; the isolation layer is composed of silicon nitride and silicon dioxide; the via metal is made of Al and Cu materials; and the isolation layer is polished chemically to reduce the roughness of its upper surface.

[0012] Further, the sensing plane is parallel to the single chip plane; or the sensing plane is parallel to the plane occupied by the Wheatstone bridge in the anisotropic magnetoresistive sensor.

[0013] Furthermore, the anisotropic magnetoresistance sensor includes two groups of Wheatstone bridges, wherein the first group of Wheatstone bridges and the second group of Wheatstone bridges are arranged at an angle of 45 degrees, and the output of each Wheatstone bridge constitutes a first signal output by the anisotropic magnetoresistance sensor; the Hall sensor is a vertical Hall sensor, which includes at least two vertical Hall devices, and the output of each vertical Hall device constitutes a second signal output by the Hall sensor.

[0014] Furthermore, the Hall sensor includes two vertical Hall devices, wherein the current direction of one vertical Hall device forms an angle of 90 degrees with the current direction of the other vertical Hall device.

[0015] Furthermore, the vertical Hall device includes: p-type silicon; n-type silicon extending from the upper surface of the p-type silicon into the p-type silicon to form a potential well; and an electrode located on the upper surface of the n-type silicon.

[0016] Furthermore, the electrode located on the upper surface of the n-type silicon includes a power supply terminal VDD, two ground terminals, and a first output terminal and V+ and a second output terminal V-, wherein the power supply terminal VDD is located in the middle, and the first output terminal V+ and the second output terminal V- are located on both sides of the power supply terminal VDD; the two ground terminals are located on both sides of the power supply terminal VDD.

[0017] Compared with the prior art, the 360-degree magnetic angle sensor in the present invention includes an anisotropic magnetoresistive sensor, a Hall sensor and a signal processing circuit integrated in a single chip. Among them, the Hall sensor uses a vertical Hall sensor to sense the magnetic field parallel to the chip plane (or chip surface); the signal processing circuit determines the interval of the magnetic angle (angle or external magnetic field angle) from 0 to 180 degrees or 180 to 360 degrees based on the output of the vertical Hall sensor, and a more accurate angle is obtained by combining the output of the AMR sensor with the interval of the magnetic angle to obtain a high-precision magnetic angle of 0 to 360 degrees.

Brief Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0019] Figure 1 is a longitudinal cross-sectional schematic diagram of a single-chip 360-degree magnetic angle sensor in one embodiment of the present invention;

[0020] Figure 2 for Figure 1 A schematic longitudinal cross-sectional view of a vertical Hall device in a vertical Hall sensor in one embodiment is shown;

[0021] Figure 3 In one embodiment Figure 1 Schematic diagram of the equivalent bridge of the AMR sensor shown;

[0022] FIG. 4( a ) is a graph showing the relationship between the outputs of two groups of vertical Hall devices in a vertical Hall sensor of the present invention and the external magnetic field angle in one embodiment;

[0023] FIG. 4( b ) is a graph showing the relationship between the outputs of two groups of Wheatstone bridges of the AMR sensor of the present invention and the external magnetic field angle in one embodiment. [Specific implementation method]

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] The term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments. Unless otherwise specified, the words "connected", "connected", and "connected" herein that indicate electrical connection all refer to direct or indirect electrical connection.

[0026] Please refer to Figure 1 As shown, it is a longitudinal cross-sectional schematic diagram of a single-chip 360-degree magnetic angle sensor in one embodiment of the present invention. Figure 1 The single-chip 360-degree magnetic angle sensor shown includes a Hall sensor, an anisotropic magnetoresistance (AMR) sensor and a signal processing circuit formed on the same silicon substrate (or semiconductor substrate) 101. The anisotropic magnetoresistance sensor generates a first signal representing the magnetic angle based on the magnetic field in the sensing plane, and the first signal has an angular range of 180 degrees; the Hall sensor generates a second signal representing the magnetic angle based on the magnetic field in the sensing plane, and the second signal has an angular range of 360 degrees; the signal processing circuit is electrically connected to the anisotropic magnetoresistance sensor and the Hall sensor, and determines the interval to which the magnetic angle belongs based on the second signal, and the interval to which the magnetic angle belongs is 0 to 180 degrees or 180 to 360 degrees, and generates a third signal representing the magnetic angle in combination with the interval to which the magnetic angle belongs and the first signal, and the third signal has an angular range of 360 degrees.

[0027] The Hall sensor and the signal processing circuit are arranged in the first structure layer 102, the AMR sensor is arranged in the second structure layer 104, and the first structure layer 102 and the second structure layer 104 are stacked on the silicon substrate 101. The first structure layer 102 provided with the Hall sensor and the signal processing circuit is located on the substrate 101; the second structure layer 104 provided with the AMR sensor is located above the first structure layer 101, and the signal processing circuit and the AMR sensor are electrically connected through a via metal (not shown). In one embodiment, the substrate 101 can be made of single crystal silicon in a standard CMOS process; the Hall sensor and the dedicated integrated circuit in the second structure layer 102 are made on the single crystal silicon substrate 101 using a standard CMOS process.

[0028] exist Figure 1 In the illustrated embodiment, the single-chip 360-degree magnetic angle sensor further includes an isolation layer 103 and a third structure layer 105. The isolation layer 103 is located between the first structure layer 102 and the second structure layer 104; the third structure layer 105 is located above the second structure layer 104. The isolation layer 103 is provided with a through hole (not shown) that runs through its thickness, and a via metal (not shown) passes through the through hole (or the via metal passes through the isolation layer) to electrically connect the AMR sensor and the signal processing circuit. The isolation layer 103 can be composed of materials such as silicon nitride and silicon dioxide, and the via metal can be made of materials such as Al and Cu. The roughness of the upper surface of the isolation layer 103 is small enough, and the roughness can be reduced by methods such as chemical mechanical polishing. The third structure layer 105 includes an AMR sensor protection layer and electrodes thereon, and the electrodes are connected to the signal processing circuit through via metals, and the output signal of the signal circuit is transmitted to the electrodes of the third structure layer 105 through the via metals.

[0029] Figure 1 The angle sensor shown is completely integrated into a single chip, and the final package body adopts wafer-level packaging, and can also adopt plastic packaging.

[0030] The Hall sensor disposed in the second structure layer 104 is a vertical Hall sensor, and its sensing plane is parallel to the single chip plane (or single chip surface).

[0031] Figure 1 The vertical Hall sensor shown includes at least two or other even number of vertical Hall devices, and the output of each vertical Hall device constitutes the second signal output by the vertical Hall sensor indicating the magnetic angle. Figure 2 As shown, it is Figure 1 FIG. 1 is a schematic longitudinal cross-sectional view of a vertical Hall device in a vertical Hall sensor in an embodiment. Figure 2A Cartesian coordinate system is defined in which the x-axis extends from left to right, the z-axis extends from bottom to top, the y-axis extends away from the viewer into the page, and the z-axis satisfies the right-hand rule with the x-axis and the y-axis.

[0032] Figure 2 The vertical Hall device shown includes an n-well 202 (eg, a potential well n+Si composed of n-type silicon) extending downward from the upper surface of a p-type substrate 201 (eg, p-type silicon p-Si) into the p-type substrate 201 , and a port group 206 located above the n-well 202 .

[0033] Figure 2 The main structure of the vertical Hall device shown is an n-well 202, and the periphery is a p-type substrate 201. When working, the current only flows in the n-well 202 in the central area. A reverse-biased PN junction is formed at the Si interface between the p-type substrate 201 and the n-well 202 to prevent leakage current.

[0034] The port group 206 includes five ports arranged at intervals from each other, namely, a power supply terminal VDD, a first ground terminal GND1, a second ground terminal GND2, a positive signal terminal V+, and a negative signal terminal V-. The five ports are arranged in sequence at intervals to form a straight line along the x-axis. The power supply terminal VDD is located in the middle, and the positive signal terminal V+ and the negative signal terminal V- are located on both sides of the power supply terminal VDD; the first ground terminal GND1 and the second ground terminal GND2 are located on the outside of the positive signal terminal V+ and the negative signal terminal V-. The positions of the power supply terminal VDD and the ground terminals GND1 and GND2 can also be interchanged.

[0035] The following introduction Figure 2 The working principle of the vertical Hall device shown.

[0036] The output terminals of the vertical Hall device are the positive signal terminal V+ and the negative signal terminal V-. The current enters the n-well 202 from the power supply terminal VDD. When an external magnetic field in the direction 205 (i.e., perpendicular to the paper and inward, in the coordinate y direction) is applied, due to the Lorentz force, the electrons in the current 203 flowing to the left will gather toward the negative signal terminal V-, and the electrons in the current 204 flowing to the right will gather in the direction away from the positive signal terminal V+. Therefore, a potential difference is generated between the positive signal terminal V+ and the negative signal terminal V-, and the potential difference is proportional to the external magnetic field.

[0037] In one embodiment, the vertical Hall sensor includes two vertical Hall devices, and the current direction of one vertical Hall device is at an angle of 90 degrees to the current direction of the other vertical Hall device. Please refer to FIG4(a), which is a graph showing the relationship between the output of the two vertical Hall devices in the vertical Hall sensor of the present invention and the external magnetic field angle in one embodiment, wherein the output of one vertical Hall device changes with the external magnetic field angle of sinθ, specifically as shown in FIG4(a) 403, and the output of the other vertical Hall device changes with the external magnetic field angle of cosθ, specifically as shown in FIG4(a) 404, and the magnetic angle of the 360-degree period is calculated by inverse tangent or an equivalent method.

[0038] See also Figure 3 As shown, in one embodiment Figure 1 Schematic diagram of the equivalent bridge of the AMR sensor shown. Figure 3 A rectangular coordinate system is defined in which the x-axis extends from left to right and the y-axis extends from bottom to top. Figure 3 The illustrated AMR sensor includes a first Wheatstone bridge 104 a and a second Wheatstone bridge 104 b .

[0039] The first Wheatstone bridge 104a includes resistor elements (or bridge arm resistors) R11, R12, R13 and R14, wherein the resistor R11 is connected between the power supply terminal VDD1 and the signal negative terminal V1-; the resistor R12 is connected between the signal negative terminal V1- and the ground terminal GND1; the resistor R13 is connected between the signal positive terminal V1+ and the ground terminal GND1; the resistor R14 is connected between the power supply terminal VDD1 and the signal positive terminal V1+; the output terminals of the first Wheatstone bridge 104a are the signal positive terminal V1+ and the signal negative terminal V1-. The second Wheatstone bridge 104b includes resistor elements R21, R22, R23 and R24, wherein the resistor R21 is connected between the power supply terminal VDD2 and the signal negative terminal V2-; the resistor R22 is connected between the signal negative terminal V2- and the ground terminal GND2; the resistor R23 is connected between the signal positive terminal V2+ and the ground terminal GND2; the resistor R24 ​​is connected between the power supply terminal VDD2 and the signal positive terminal V2+; the output terminals of the second Wheatstone bridge 104b are the signal positive terminal V2+ and the signal negative terminal V2-.

[0040] Figure 3The first Wheatstone bridge 104a and the second Wheatstone bridge 104b are shown to form an angle of 45 degrees, that is, the direction of each resistor element in the second Wheatstone bridge 104b is offset by 45 degrees from the direction of the corresponding resistor element in the first Wheatstone bridge 104a. For example, the resistor elements R11, R12, R13 and R14 in the first Wheatstone bridge 104a are offset by 45 degrees relative to the resistor elements R21, R22, R23 and R24 in the second Wheatstone bridge 104b. The AMR resistance is only related to the angle between the magnetization direction of the magnetic layer and the current, and the angular period is 180 degrees. When the direction of the applied magnetic field H is θ with the x-axis direction, the bridge arm resistance R14 in the first Wheatstone bridge 104a is equal to R ⊥ +(R ║ -R ⊥ )cos 2 θ,R11=R ⊥ +(R ║ -R ⊥ )sin 2 θ, R11 = R13, R12 = R14, where R ⊥ is the resistance of the bridge arm when the magnetization direction is perpendicular to the current direction, R ║ is the resistance of the bridge arm when the magnetization direction is parallel to the current direction. The output of the first Wheatstone bridge 104a is: V 1+ -V 1- =(R13-R12) / (R11+R12)=AMR / (2+AMR)cos2θ·V DD1 , where AMR is the anisotropic magnetoresistance ratio, and AMR = (R ║ -R ⊥ ) / R ⊥ Similarly, the output of the second Wheatstone bridge 104b is: V 2+ -V 2- =(R23-R22) / (R21+R22)=AMR / (2+AMR)sin2θ·V DD2 , the two bridge power supply voltages are V DD1 and V DD2 The output corresponding to the first Wheatstone bridge 104a is shown as 402 in FIG. 4(b), and the output corresponding to the second Wheatstone bridge 104b is shown as 401 in FIG. 4(b). Please refer to FIG. 4(b), which is a graph showing the relationship between the output of the two groups of Wheatstone bridges in the AMR sensor of the present invention and the external magnetic field angle in one embodiment.

[0041] It should be noted that Figure 1The AMR sensor in the AMR sensor is composed of at least two groups of Wheatstone bridges, and the output of each Wheatstone bridge constitutes a first signal representing a magnetic angle output by the AMR sensor; the sensing plane is parallel to a plane occupied by the Wheatstone bridges in the AMR sensor.

[0042] The second structural layer 104 is also provided with all the dedicated integrated circuits (i.e., signal processing circuits) of the single-chip 360-degree magnetic angle sensor. The signal processing circuit determines whether the magnetic angle is in the range of 0 to 180 or 180 to 360 degrees based on the output signal of the Hall sensor; the signal processing circuit outputs a magnetic angle in the range of 0-360 degrees based on the output signal of the AMR sensor and the interval to which the magnetic field angle belongs. In one embodiment, the processing circuit includes a circuit module for implementing amplification and filtering of Hall / AMR sensor signals, a circuit module for calculating specific angle values ​​of amplified and filtered sine and cosine signals, a circuit module for determining whether the magnetic field angle is in the range of 0 to 180 or 180 to 360 degrees, a circuit module for outputting a high-precision angle in the range of 360 degrees in combination with the Hall and AMR signals, and other necessary circuit modules.

[0043] In summary, the single-chip 360-degree magnetic angle sensor in the present invention combines an AMR sensor and a vertical Hall device, which can not only combine the high precision of the AMR sensor, but also measure a 360-degree period, and only needs to apply an in-plane magnetic field (a magnetic field parallel to the plane of the single chip) to distinguish the angle. In addition, the single-chip 360-degree magnetic angle sensor in the present invention is integrated into a single chip, which can not only achieve high-precision angle measurement within a 360-degree range, but also reduce the volume, cost and angle error caused by packaging.

[0044] In the present invention, words such as “connect”, “connected”, “connected”, “connected”, etc. indicating electrical connection, if not otherwise specified, indicate direct or indirect electrical connection.

[0045] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the content disclosed in the present invention should be included in the protection scope recorded in the claims.

Claims

1. A 360-degree magnetic angle sensor, characterized in that: It includes: an anisotropic magnetoresistive sensor that generates a first signal representing a magnetic angle based on a magnetic field in a sensing plane, the first signal having an angular range of 180 degrees; a Hall sensor that generates a second signal representing a magnetic angle based on the magnetic field in the sensing plane, the second signal having an angular range of 360 degrees; A signal processing circuit is electrically connected to the anisotropic magnetoresistive sensor and the Hall sensor, and determines the interval to which the magnetic angle belongs based on the second signal, the interval to which the magnetic angle belongs is 0 to 180 degrees or 180 to 360 degrees, and generates a third signal representing the magnetic angle in combination with the interval to which the magnetic angle belongs and the first signal, and the third signal has an angular range of 360 degrees. The Hall sensor is a vertical Hall sensor.

2. The 360-degree magnetic angle sensor according to claim 1, characterized in that: The anisotropic magnetoresistive sensor, the Hall sensor and the signal processing circuit are integrated in a single chip.

3. The 360-degree magnetic angle sensor according to claim 2, characterized in that: The single chip includes a substrate, and a first structure layer and a second structure layer stacked on the substrate. The Hall sensor and the signal processing circuit are arranged in the first structural layer; The anisotropic magnetoresistive sensor is disposed in the second structural layer.

4. The 360-degree magnetic angle sensor according to claim 3, characterized in that: The first structural layer is located on the substrate; The second structural layer is located above the first structural layer.

5. The 360-degree magnetic angle sensor according to claim 4, characterized in that: The single chip further includes an isolation layer and a third structural layer. The isolation layer is located between the first structure layer and the second structure layer, and the via metal passes through the isolation layer to electrically connect the anisotropic magnetoresistive sensor and the signal processing circuit; The third structural layer is located above the second structural layer, and the third structural layer includes an anisotropic magnetoresistive sensor protection layer and electrodes thereon, and the electrodes are connected to the signal processing circuit through via metals.

6. The 360-degree magnetic angle sensor according to claim 5, characterized in that: The substrate is made of single crystal silicon in a standard CMOS process; The Hall sensor and the dedicated integrated circuit in the second structural layer are manufactured on a single crystal silicon substrate using a standard CMOS process; The isolation layer is composed of silicon nitride and silicon dioxide; The via metal is made of Al or Cu materials; The isolation layer adopts chemical mechanical polishing to reduce the roughness of its upper surface.

7. The 360-degree magnetic angle sensor according to claim 1, characterized in that: The sensing plane is parallel to the single chip plane; or The sensing plane is parallel to a plane occupied by a Wheatstone bridge in the anisotropic magnetoresistive sensor.

8. The 360-degree magnetic angle sensor according to claim 2, characterized in that: The anisotropic magnetoresistance sensor comprises two groups of Wheatstone bridges, wherein the first group of Wheatstone bridges and the second group of Wheatstone bridges are arranged at an angle of 45 degrees, and the output of each Wheatstone bridge constitutes a first signal output by the anisotropic magnetoresistance sensor; The Hall sensor includes at least two vertical Hall devices, and the outputs of the respective vertical Hall devices constitute a second signal output by the Hall sensor.

9. The 360-degree magnetic angle sensor according to claim 8, characterized in that: The Hall sensor includes two vertical Hall devices, wherein the current direction of one vertical Hall device forms an angle of 90 degrees with the current direction of the other vertical Hall device.

10. The 360-degree magnetic angle sensor according to claim 8, characterized in that: The vertical Hall device comprises: p-type silicon; n-type silicon extending from the upper surface of the p-type silicon into the p-type silicon to form a potential well; and an electrode located on the upper surface of the n-type silicon.

11. The 360-degree magnetic angle sensor according to claim 10, characterized in that: The electrodes located on the upper surface of the n-type silicon include a power supply terminal VDD, two ground terminals, a first output terminal V+ and a second output terminal V-. The power supply terminal VDD is located in the middle, the first output terminal V+ and the second output terminal V− are located on both sides of the power supply terminal VDD; and the two ground terminals are located on both sides of the power supply terminal VDD.

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