Accelerometer

Abstract

To achieve linearity characteristic with little characteristic error up to a high temperature region while reducing electrostatic fracture risk in assembling an acceleration sensor.SOLUTION: An acceleration sensor 1 includes, for example, a sensor device 10 configured to generate an acceleration signal S10 and a signal processor 20 configured to process the acceleration signal S10. The sensor device and the signal processor are sealed in a single package. The signal processor 20 includes: a signal input terminal P2 configured to receive an external input of the acceleration signal S10; a first electrostatic protection element D1 configured to be connected between the signal input terminal P2 and a first node to which a first voltage VDD is applied; and a second electrostatic protection element D2 configured to be connected between the signal input terminal P2 and a second node to which a second voltage GND is applied. The first electrostatic protection element D1 and the second electrostatic protection element D2 have the same structure and have the same leakage current characteristics.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] This disclosure relates to an acceleration sensor.

Background Art

[0002] Acceleration sensors are used in various applications such as in-vehicle devices and industrial devices as a means to grasp the posture, movement, or vibration state of an object.

[0003] As an example of the related prior art, Patent Document 1 can be cited.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, there has been room for study regarding realizing linear characteristics with few characteristic errors up to a high-temperature region while reducing the risk of electrostatic breakdown during assembly in conventional acceleration sensors.

Means for Solving the Problems

[0006] For example, the acceleration sensor disclosed herein is an acceleration sensor comprising a sensor device configured to generate an acceleration signal and a signal processing device configured to process the acceleration signal, all packaged together in a single package, wherein the signal processing device includes a signal input terminal configured to accept an external input of the acceleration signal, a first electrostatic protection element configured to be connected between the signal input terminal and a first node to which a first voltage is applied, and a second electrostatic protection element configured to be connected between the signal input terminal and a second node to which a second voltage is applied, and the first and second electrostatic protection elements are identical in structure and have identical leakage current characteristics.

[0007] Further details regarding other features, elements, steps, advantages, and characteristics will become clearer from the embodiments for carrying out the invention and the accompanying drawings. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide an acceleration sensor that can achieve linear characteristics with minimal characteristic errors up to high temperature ranges while reducing the risk of electrostatic discharge during assembly. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows the overall configuration of the acceleration sensor. [Figure 2] Figure 2 shows an example of a sensor device configuration. [Figure 3] Figure 3 shows an example of a signal processing device configuration. [Figure 4] Figure 4 shows an example of an input amplifier configuration. [Figure 5] Figure 5 shows an example of the operation of an input amplifier. [Figure 6] Figure 6 shows a measure to prevent electrostatic discharge in a signal processing device (first embodiment). [Figure 7]Figure 7 shows a measure to prevent electrostatic discharge in a signal processing device (second embodiment). [Figure 8] Figure 8 shows a measure to prevent electrostatic discharge in a signal processing device (third embodiment). [Figure 9] Figure 9 shows a measure to prevent electrostatic discharge in a signal processing device (fourth embodiment). [Figure 10] Figure 10 shows the vertical structure of an electrostatic protection diode. [Figure 11] Figure 11 shows the temperature characteristics of the input offset. [Modes for carrying out the invention]

[0010] <Accelerometer> Figure 1 shows the overall configuration of an acceleration sensor. The acceleration sensor 1 in this example configuration is a module for detecting the attitude, movement, or vibration state of the application in which it is installed (such as in-vehicle equipment and industrial equipment), and consists of a sensor device 10 and a signal processing device 20 sealed in a single package.

[0011] The sensor device 10 includes an X-axis sensor unit 11, a Y-axis sensor unit 12, and a Z-axis sensor unit 13, and generates a 3-axis acceleration signal S10. The acceleration signal S10 may be, for example, an analog voltage signal. In order to miniaturize the sensor device 10, a capacitive method using MEMS (micro electro mechanical system) technology may be adopted as the acceleration detection method (details will be described later).

[0012] The signal processing device 20 is a semiconductor integrated circuit device (such as an ASIC [application-specific integrated circuit]) that processes the acceleration signal S10 using various algorithms. Referring to this figure, the signal processing device 20 includes an input amplifier 21, an A / D [analog-to-digital] converter 22, a processor 23, and an interface 24.

[0013] The input amplifier 21 amplifies the acceleration signal S10 to generate an amplified acceleration signal S21.

[0014] The A / D converter 22 converts the amplified acceleration signal S21 into a digital signal S22.

[0015] The processor 23 generates a sensor output signal S23 from the digital signal S22. As the processor 23, a DSP [digital signal processor] and a buffer may be used.

[0016] The interface 24 outputs the sensor output signal S23 externally in accordance with a predetermined protocol (such as I2C [inter - integrated circuit] and SPI [serial peripheral interface]). Also, the interface 24 receives external inputs of various control signals and transmits them to the processor 23. Speaking in terms of this figure, the interface 24 includes, for example, an SDA port and an SCL port as input / output ports compliant with the I2C protocol.

[0017] <Sensor device> FIG. 2 is a diagram showing a configuration example of a sensor device 10 (particularly MEMS elements respectively used as the X - axis sensor section 11, Y - axis sensor section 12, and Z - axis sensor section 13). The MEMS element 100 of this configuration example includes a fixed electrode 101, a variable electrode 102, and an elastic support member 103.

[0018] The fixed electrode 101 is configured such that its position remains unchanged regardless of the acceleration applied to the sensor device 10. As shown in this figure, there may be a plurality of fixed electrodes 101.

[0019] The variable electrode 102 includes a protrusion 102a extending so as to face the fixed electrode 101, and is elastically supported such that the relative position between the protrusion 102a and the fixed electrode 101 (and thus the electrode distance d) changes in response to the acceleration applied to the sensor device 10.

[0020] The elastic support member 103 (for example, a leaf spring) elastically supports the variable electrode 102.

[0021] When acceleration is applied to the MEMS element 100, the variable electrode 102 moves in the left-right direction of the paper, so the distance d between the fixed electrode 101 and the variable electrode 102 (= projection 102a) changes. As a result, the magnitude of the capacitance formed between the fixed electrode 101 and the variable electrode 102 changes. Therefore, by outputting the voltage generated between the fixed electrode 101 and the variable electrode 102 as an acceleration signal S10, acceleration can be measured linearly.

[0022] <Signal Processing Device> Figure 3 shows an example configuration of the signal processing device 20 (particularly the front-end area including the sensor device 10).

[0023] The sensor device 10 is depicted as a MEMS capacitance model including capacitors Ca and Cb. In this diagram, the first terminal of capacitor Ca is connected to the application terminal of the first drive voltage Va. Both the second terminal of capacitor Ca and the first terminal of capacitor Cb are connected to pad P1. The second terminal of capacitor Cb is connected to the application terminal of the second drive voltage Vb. The capacitance values ​​of capacitors Ca and Cb change according to the acceleration applied to the sensor device 10.

[0024] The signal processing device 20 includes, in addition to the input amplifier 21 and A / D converter 22 described above, a pad P2, an offset correction unit 26, and an offset adjustment unit 27.

[0025] Pad P2 corresponds to a signal input terminal that receives an external input of the acceleration signal S10. A wire W1 is bonded between pad P1, which is provided on the sensor device 10, and pad P2, which is provided on the signal processing device 20.

[0026] As mentioned earlier, the input amplifier 21 amplifies the acceleration signal S10 to generate the amplified acceleration signal S21. Referring to this figure, the input amplifier 21 includes amplifiers A1 and A2, capacitors C1 to C3, and resistor R1.

[0027] The inverting input terminal (-) of amplifier A1 and the first terminal of capacitor C1 are both connected to pad P2. The output terminal of amplifier A1 (= application terminal of amplifier output signal SA1) and the second terminal of capacitor C1 are both connected to the first terminal of resistor R1. The second terminal of resistor R1 is connected to the first terminal of capacitor C3. The inverting input terminal (-) of amplifier A2 and the first terminal of capacitor C2 are both connected to the second terminal of capacitor C3. The output terminal of amplifier A2 and the second terminal of capacitor C2 are both connected to the application terminal of the amplified acceleration signal S21. The non-inverting input terminals (+) of amplifiers A1 and A2 are both connected to the application terminal of the bias voltage Vm.

[0028] Furthermore, the acceleration range can be arbitrarily set by the user by adjusting the capacitance value of capacitor C1. In addition, the gain of the input amplifier 21 can be trimmed by adjusting the capacitance value of capacitor C2.

[0029] The offset correction unit 26 corrects the input offset temperature gradient of the acceleration signal S10 to reduce its value.

[0030] The offset adjustment unit 27 adjusts the input offset of the acceleration signal S10 by trimming or other means.

[0031] <Input Amplifier> Figure 4 shows an example configuration of the input amplifier 21. In this example configuration, the input amplifier 21 includes, in addition to the amplifier A1 and capacitor C1 mentioned earlier, capacitor C4 and switches SW1 and SW2.

[0032] The first terminal of switch SW1 is connected to the inverting input terminal (-) of amplifier A1. The second terminal of switch SW1 and the first terminal of switch SW2 are both connected to the output terminal of amplifier A1. The second terminal of switch SW2 and the first terminal of capacitor C4 are both connected to the application terminal of the amplifier output signal SA1. The second terminal of capacitor C4 is connected to the application terminal of the bias voltage Vm.

[0033] Figure 5 shows an example of the operation of the input amplifier 21 (particularly amplifier A1), depicting, from top to bottom, the first drive voltage Va, the second drive voltage Vb, and the operating states of switches SW1 and SW2 respectively (H = on, L = off).

[0034] In the first phase φ1 (times t1 to t3), the first drive voltage Va is set to a high level (e.g., Va = VDD), and the second drive voltage Vb is set to a low level (e.g., Vb = GND). That is, the inter-electrode voltage (Va-Vb) applied between the fixed electrode 101 and the variable electrode 102 of the MEMS element 100 used in the sensor device 10 is positive. At this time, the acceleration signal S10(φ1) is output as a voltage signal obtained by capacitively dividing the positive inter-electrode voltage (Va-Vb) using capacitors Ca and Cb. Switch SW1 is switched from the ON state to the OFF state midway through the first phase φ1 (time t2). On the other hand, switch SW2 is always kept in the OFF state during the first phase φ1.

[0035] In the second phase φ2 (times t3 to t5), the first drive voltage Va is set to a low level (e.g., Va=GND) and the second drive voltage Vb is set to a high level (e.g., Vb=VDD). That is, the inter-electrode voltage (Va-Vb) applied between the fixed electrode 101 and the variable electrode 102 of the MEMS element 100 used in the sensor device 10 becomes negative. At this time, the acceleration signal S10(φ2) is output as a voltage signal obtained by capacitively dividing the negative inter-electrode voltage (Va-Vb) using capacitors Ca and Cb. Switch SW1 is kept in the off state throughout the second phase φ2. On the other hand, switch SW2 is switched from the off state to the on state midway through the second phase φ2 (time t4).

[0036] In the third phase φ3 (times t5 to t7), both the first drive voltage Va and the second drive voltage Vb are set to a middle level (for example, Va=Vb=Vm=VDD / 2). That is, the inter-electrode voltage (Va-Vb) applied between the fixed electrode 101 and the variable electrode 102 of the MEMS element 100 used in the sensor device 10 becomes 0V, and consequently, the acceleration signal S10 (φ3) also becomes 0V. Switch SW1 is switched from the off state to the on state midway through the third phase φ3 (time t6). On the other hand, switch SW2 is always kept in the off state during the third phase φ3.

[0037] Through the above series of operations, the input amplifier 21 generates an amplifier output signal SA1 (=VDD × (Ca - Cb) / C1) corresponding to the difference between the acceleration signal S10 (φ1) obtained in the first phase φ1 and the acceleration signal S10 (φ2) obtained in the second phase φ2. Therefore, the amplifier output signal SA1 becomes less susceptible to the effects of relative variations in capacitors Ca and Cb and superimposed noise.

[0038] <Measures against electrostatic discharge (first embodiment)> Figure 6 shows a measure to prevent electrostatic discharge (first embodiment) in the signal processing device 20. In this embodiment, the signal processing device 20 includes a pad P3 and electrostatic protection diodes D3 and D4 in addition to the previously described components.

[0039] Pad P3 corresponds to a signal output terminal that externally outputs the sensor output signal S23. A wire W2 is bonded between pad P3 provided in the signal processing device 20 and the lead frame LF drawn out to the outside of the package of the acceleration sensor 1.

[0040] The anode of the electrostatic protection diode D3 (corresponding to the third electrostatic protection element) is connected to pad P3. The cathode of the electrostatic protection diode D3 is connected to the applied end of the power supply voltage VDD (corresponding to the first node). The electrostatic protection diode D3 connected in this way functions to discharge this positive surge (> VDD) to the applied end of the power supply voltage VDD when a positive surge is applied to pad P3. As the electrostatic protection diode D3, the body diode of a PMOSFET [P-channel type metal oxide semiconductor field effect transistor] is generally used.

[0041] The cathode of the electrostatic protection diode D4 (corresponding to the fourth electrostatic protection element) is connected to pad P3. The anode of the electrostatic protection diode D4 is connected to the applied end of the ground voltage GND (corresponding to the second node). The electrostatic protection diode D4 connected in this way functions to discharge this negative surge (< GND) to the applied end of the ground voltage GND when a negative surge is applied to pad P3. As the electrostatic protection diode D4, the body diode of an NMOSFET [N-channel type MOSFET] is generally used.

[0042] In this way, in the signal processing device 20 of the present embodiment, only the electrostatic protection diodes D3 and D4 are provided on pad P3 connected to the lead frame LF, and no electrostatic protection element is provided on pad P2 connected to pad P1 of the sensor device 10. Therefore, there is a concern about the risk of electrostatic breakdown during the assembly of the acceleration sensor 1.

[0043] <Countermeasures against Electrostatic Discharge (Second Embodiment)> FIG. 7 is a diagram showing electrostatic breakdown countermeasures (second embodiment) of the signal processing device. The signal processing device 20 of this embodiment is based on the foregoing first embodiment (FIG. 6), and a current limiting resistor R2 is added between the pad P2 and the amplifier A1.

[0044] According to this embodiment, compared with the foregoing first embodiment (FIG. 6), the electrostatic breakdown resistance of the pad P2 can be slightly increased. However, the effect of reducing the electrostatic breakdown risk is not necessarily sufficient, and depending on the magnitude of the surge applied to the pad P2, there is a possibility that the signal processing device 20 may be destroyed.

[0045] <Electrostatic breakdown countermeasures (third embodiment)> FIG. 8 is a diagram showing electrostatic breakdown countermeasures (third embodiment) of the signal processing device. The signal processing device 20 of this embodiment is based on the foregoing first embodiment (FIG. 6), and electrostatic protection diodes D5 and D6 are added.

[0046] The anode of the electrostatic protection diode D5 is connected to the pad P2. The cathode of the electrostatic protection diode D5 is connected to the application terminal of the power supply voltage VDD. The electrostatic protection diode D5 connected in this way functions to discharge the positive surge (>VDD) applied to the pad P2 to the application terminal of the power supply voltage VDD. As the electrostatic protection diode D5, similar to the foregoing electrostatic protection diode D3, the body diode of the PMOSFET is generally used.

[0047] The cathode of the electrostatic protection diode D6 is connected to the pad P2. The anode of the electrostatic protection diode D6 is connected to the application terminal of the ground voltage GND. The electrostatic protection diode D6 connected in this way functions to discharge the negative surge (<GND) applied to the pad P2 to the application terminal of the ground voltage GND. As the electrostatic protection diode D6, similar to the foregoing electrostatic protection diode D4, the body diode of the NMOSFET is generally used.

[0048] According to this embodiment, the electrostatic discharge resistance of the pad P2 can be significantly improved compared to the first embodiment (Figure 6) and the second embodiment (Figure 7).

[0049] However, since electrostatic protection diodes D5 and D6 have significantly different structures, their respective leakage current characteristics tend to vary. Consequently, the difference in leakage current flowing through electrostatic protection diodes D5 and D6 can flow into pad P2 as an error current Ierr. When such an error current Ierr flows, an unnecessary input offset is superimposed on the acceleration signal S10, degrading the accuracy of acceleration detection.

[0050] Furthermore, the MOS-structured electrostatic protection diodes D5 and D6 have two leakage current paths: one through the MOSFET and another through the body diode. As a result, the leakage current flowing through each of the electrostatic protection diodes D5 and D6 is relatively large. Consequently, the error current Ierr also tends to be relatively large, and consequently, the input offset of the acceleration signal S10 tends to be large.

[0051] In particular, the acceleration signal S10 generated by the sensor device 10 (more specifically, the MEMS element 100) is a minute analog voltage signal. Therefore, in order to improve the accuracy of acceleration detection, it is important to reduce the error current Ierr as much as possible.

[0052] Furthermore, if the structures of electrostatic protection diodes D5 and D6 are different, the parasitic capacitance associated with them will also differ significantly. This can also be a factor that degrades the accuracy of acceleration detection.

[0053] <Measures against electrostatic discharge (Fourth embodiment)> Figure 9 shows a measure to prevent electrostatic discharge (fourth embodiment) in the signal processing device. The signal processing device 20 of this embodiment is based on the third embodiment (Figure 8) described above, but the electrostatic protection diodes D5 and D6 described above are replaced with electrostatic protection diodes D1 and D2, respectively.

[0054] The anode of the electrostatic protection diode D1 (corresponding to the first electrostatic protection element) is connected to the pad P2. The cathode of the electrostatic protection diode D1 is connected to the applied end of the power supply voltage VDD. The electrostatic protection diode D1 connected in this way functions to discharge a positive surge (>VDD) applied to the pad P2 to the applied end of the power supply voltage VDD. In this regard, it is no different from the aforementioned electrostatic protection diode D5. Note that, unlike the aforementioned electrostatic protection diodes D3 and D5, a diode with a PN structure (details will be described later) is used as the electrostatic protection diode D1.

[0055] The cathode of the electrostatic protection diode D2 (corresponding to the second electrostatic protection element) is connected to the pad P2. The anode of the electrostatic protection diode D2 is connected to the applied end of the ground voltage GND. The electrostatic protection diode D2 connected in this way functions to discharge a negative surge (<GND) applied to the pad P2 to the applied end of the ground voltage GND. In this regard, it is no different from the aforementioned electrostatic protection diode D6. Note that, unlike the aforementioned electrostatic protection diodes D4 and D6, a diode with a PN structure (details will be described later) is generally used as the electrostatic protection diode D2.

[0056] As described above, in the signal processing device 20 of this embodiment, since both the electrostatic protection diodes D1 and D2 have the same structure (for example, a PN structure), they basically have the same leakage current characteristics. Therefore, since the leakage currents flowing through the electrostatic protection diodes D1 and D2 are basically the same value, an error current Ierr corresponding to the difference is less likely to flow. As a result, the input offset of the acceleration signal S10 can be reduced, and thus the detection accuracy of acceleration can be improved.

[0057] Furthermore, unlike the MOS structure mentioned earlier, the PN structure electrostatic protection diodes D1 and D2 do not have a leakage current path through a MOSFET. Therefore, the leakage current flowing through each of the electrostatic protection diodes D1 and D2 is inherently small, and they cancel each other out, resulting in an error current Ierr of almost zero. Consequently, the input offset of the acceleration signal S10 is also almost zero.

[0058] Furthermore, the bias voltage Vm used to determine the bias point of pad P2 should be set to the midpoint voltage of the power supply voltage VDD and the ground voltage GND (=(VDD-GND) / 2). With this bias setting, the voltages applied between the anode and cathode of electrostatic protection diodes D1 and D2 will be the same. Consequently, the leakage currents flowing through electrostatic protection diodes D1 and D2 will approach the same value, making it possible to reduce the error current Ierr (and thus the input offset of the acceleration signal S10) corresponding to the difference.

[0059] <Electrostatic protection diode> Figure 10 shows the vertical structure of electrostatic protection diodes D1 and D2. The semiconductor device 200 (corresponding to the signal processing device 20 mentioned earlier) on which electrostatic protection diodes D1 and D2 are formed comprises floating N-type semiconductor regions 210 and 220.

[0060] A P-type well 211 is formed near the surface of the floating N-type semiconductor region 210. A high-density N-type semiconductor region 212 and a high-density P-type semiconductor region 213 surrounding the high-density N-type semiconductor region 212 are formed in the P-type well 211. At least a portion of the high-density P-type semiconductor region 213 is exposed to the surface without being covered by the protective layer 230, and a pad potential PAD (=acceleration signal S10 of pad P2) is applied to it. At least a portion of the high-density N-type semiconductor region 212 is exposed to the surface without being covered by the protective layer 230, and a power supply voltage VDD is applied to it.

[0061] Furthermore, a high-concentration N-type semiconductor region 214 is formed near the surface of the floating N-type semiconductor region 210, adjacent to and surrounding the P-type well 211. At least a portion of the high-concentration N-type semiconductor region 214 is exposed to the surface without being covered by the protective layer 230, and a first floating potential FL1 (not shown) is applied to it.

[0062] A P-type well 221 is formed near the surface of the floating N-type semiconductor region 220. The P-type well 221 has a high-density N-type semiconductor region 222 and a high-density P-type semiconductor region 223 surrounding the high-density N-type semiconductor region 222. At least a portion of the high-density P-type semiconductor region 223 is exposed to the surface without being covered by the protective layer 230, and a ground voltage GND is applied to it. At least a portion of the high-density N-type semiconductor region 222 is exposed to the surface without being covered by the protective layer 230, and the aforementioned pad potential PAD is applied to it.

[0063] Furthermore, a high-concentration N-type semiconductor region 224 is formed near the surface of the floating N-type semiconductor region 220, adjacent to and surrounding the P-type well 221. At least a portion of the high-concentration N-type semiconductor region 224 is exposed to the surface without being covered by the protective layer 230, and a second floating potential FL2 (not shown) is applied to it.

[0064] The electrostatic protection diode D1 is formed such that the P-type well 211 (corresponding to the first P-type well) is used as the anode, and the high-concentration N-type semiconductor region 212 (corresponding to the first N-type semiconductor region) formed in the P-type well 211 is used as the cathode.

[0065] Furthermore, the electrostatic protection diode D2 is formed such that the P-type well 221 (corresponding to the second P-type well) is used as the anode, and the high-concentration N-type semiconductor region 222 (corresponding to the second N-type semiconductor region) formed in the P-type well 221 is used as the cathode.

[0066] Furthermore, it is desirable to design the first junction area between the P-type well 211 and the high-density N-type semiconductor region 212 and the second junction area between the P-type well 221 and the high-density N-type semiconductor region 222 to be identical to each other. With such a device design, the leakage current flowing through electrostatic protection diodes D1 and D2, and the associated parasitic capacitances of electrostatic protection diodes D1 and D2, respectively, become equal. Therefore, it is possible to reduce the input offset of the acceleration signal S10 and improve the accuracy of acceleration detection.

[0067] <Input offset improvement> Figure 11 shows the temperature characteristics of the input offset in the signal processing device 20. The solid line shows the temperature characteristics of the fourth embodiment (Figure 9), and the dashed line shows the temperature characteristics of the third embodiment (Figure 8).

[0068] As shown by the dashed line in this figure, in the acceleration sensor 1 of the third embodiment (Figure 8), the structures of electrostatic protection diodes D5 and D6 (and consequently their leakage current characteristics) are significantly different, resulting in a larger input offset, especially in the high-temperature range.

[0069] In contrast, as shown by the solid line in this figure, the acceleration sensor 1 of the fourth embodiment (Figure 9) has the same structure (and consequently, leakage current characteristics) for both electrostatic protection diodes D1 and D2, resulting in a flat input offset of almost zero from low temperature to high temperature. Therefore, it is suitable for applications that require accurate acceleration detection even in high-temperature environments (e.g., automotive equipment and industrial equipment).

[0070] <Summary> The various embodiments described above will be summarized below.

[0071] For example, the acceleration sensor disclosed herein is an acceleration sensor comprising a sensor device configured to generate an acceleration signal and a signal processing device configured to process the acceleration signal, all packaged together in a single package, wherein the signal processing device includes a signal input terminal configured to accept an external input of the acceleration signal, a first electrostatic protection element configured to be connected between the signal input terminal and a first node to which a first voltage is applied, and a second electrostatic protection element configured to be connected between the signal input terminal and a second node to which a second voltage is applied, and the first and second electrostatic protection elements are both identical in structure and have the same leakage current characteristics (first configuration).

[0072] In the acceleration sensor according to the first configuration described above, the acceleration signal may be configured to be an analog signal (second configuration).

[0073] In the acceleration sensor according to the first or second configuration described above, the first electrostatic protection element and the second electrostatic protection element may both be electrostatic protection diodes with a PN structure (third configuration).

[0074] In the acceleration sensor according to the third configuration described above, the first electrostatic protection element may be configured such that the first P-type well is the anode and the first N-type semiconductor region formed in the first P-type well is the cathode, and the second electrostatic protection element may be configured such that the second P-type well is the anode and the second N-type semiconductor region formed in the second P-type well is the cathode (fourth configuration).

[0075] In the acceleration sensor according to the fourth configuration described above, the first junction area between the first P-type well and the first N-type semiconductor region may be equal to the second junction area between the second P-type well and the second N-type semiconductor region (fifth configuration).

[0076] In an acceleration sensor according to any of the first to fifth configurations described above, the signal input terminal may be configured to be biased to the midpoint voltage of the first voltage and the second voltage (sixth configuration).

[0077] In an acceleration sensor according to any of the above configurations 1 to 6, the signal processing device may be configured to include an input amplifier configured to amplify the acceleration signal and generate an amplified acceleration signal, an A / D converter configured to convert the amplified acceleration signal into a digital signal, a processor configured to generate a sensor output signal from the digital signal, and an interface configured to output the sensor output signal to an external source (configuration 7).

[0078] The acceleration sensor according to the seventh configuration described above may further include a signal output terminal configured to output the sensor output signal to an external source, a third electrostatic protection element configured to be connected between the signal output terminal and the first node, and a fourth electrostatic protection element configured to be connected between the signal output terminal and the second node (eighth configuration).

[0079] In the acceleration sensor according to the seventh or eighth configuration described above, the signal processing device may further include an offset correction unit configured to reduce the temperature gradient of the offset of the acceleration signal, and an offset adjustment unit configured to trim and adjust the offset (the ninth configuration).

[0080] In an acceleration sensor according to any of the above configurations 1 to 9, the sensor device may include a fixed electrode and a variable electrode configured such that its relative position to the fixed electrode changes in accordance with the acceleration applied to the sensor device, and may output a voltage corresponding to the change in the distance between the fixed electrode and the variable electrode as the acceleration signal (configuration 10).

[0081] <Other variations> Furthermore, the various technical features disclosed herein can be modified in various ways, in addition to the embodiments described above, without departing from the spirit of the technical creation. In other words, the embodiments described above should be considered in all respects to be illustrative and not restrictive, and the technical scope of this disclosure should be defined by the claims and understood to include all modifications that fall within the meaning and scope equivalent to the claims. [Explanation of symbols]

[0082] 1. Accelerometer 10 Sensor device 11 X-axis sensor section 12 Y-axis sensor section 13 Z-axis sensor section 20. Signal Processing Systems (ASICs) 21 Input Amplifier 22 A / D converters 23 processors 24 Interfaces 25 Power supply and reference generation unit 26 Offset Correction Section 27 Offset adjustment section 100 MEMS elements 101 Fixed electrode 102 Variable electrode 102a Protrusion 103 Elastic support member 210, 220 Floating N-type semiconductor region 211, 221 P-type wells 212, 222 High-concentration N-type semiconductor region 213, 223 High-concentration P-type semiconductor region 214, 224 High-concentration N-type semiconductor region 230 Protective layer A1, A2 Amplifiers C1-C4, Ca, Cb capacitors D1, D2 Electrostatic protection diodes (PN structure) D3, D5 Electrostatic protection diode (PMOS body) D4, D6 Electrostatic protection diode (NMOS body) LF Lead Frame P1~P3 Pads R1, R2 resistance SW1, SW2 switches W1, W2 wires

Claims

1. A sensor device configured to generate an acceleration signal, A signal processing device configured to process the acceleration signal, An acceleration sensor in which the following are sealed in a single package: The signal processing device is A signal input terminal configured to accept an external input of the aforementioned acceleration signal, A first electrostatic protection element is configured to be connected between the signal input terminal and a first node to which a first voltage is applied, A second electrostatic protection element is configured to be connected between the signal input terminal and a second node to which a second voltage is applied, Equipped with, The first electrostatic protection element and the second electrostatic protection element are both identical in structure and have identical leakage current characteristics, and are acceleration sensors.

2. The acceleration sensor according to claim 1, wherein the acceleration signal is an analog signal.

3. The acceleration sensor according to claim 1, wherein both the first electrostatic protection element and the second electrostatic protection element are electrostatic protection diodes with a PN structure.

4. The acceleration sensor according to claim 3, wherein the first electrostatic protection element has a first P-type well as the anode and a first N-type semiconductor region formed in the first P-type well as the cathode, and the second electrostatic protection element has a second P-type well as the anode and a second N-type semiconductor region formed in the second P-type well as the cathode.

5. The acceleration sensor according to claim 4, wherein the first junction area between the first P-type well and the first N-type semiconductor region is equal to the second junction area between the second P-type well and the second N-type semiconductor region.

6. The acceleration sensor according to claim 1, wherein the signal input terminal is biased to the midpoint voltage of the first voltage and the second voltage.

7. The signal processing device is An input amplifier configured to amplify the acceleration signal and generate an amplified acceleration signal, An A / D converter configured to convert the amplified acceleration signal into a digital signal, A processor configured to generate a sensor output signal from the aforementioned digital signal, An interface configured to output the sensor output signal to an external source, An acceleration sensor according to claim 1, including the following:

8. A signal output terminal configured to output the aforementioned sensor output signal to an external source, A third electrostatic protection element configured to be connected between the signal output terminal and the first node, A fourth electrostatic protection element configured to be connected between the signal output terminal and the second node, The acceleration sensor according to claim 7, further comprising:

9. The signal processing device is An offset correction unit configured to reduce the temperature gradient of the offset of the acceleration signal, An offset adjustment unit configured to trim and adjust the aforementioned offset, The acceleration sensor according to claim 7, further comprising:

10. The acceleration sensor according to any one of claims 1 to 9, comprising a fixed electrode and a variable electrode configured such that its relative position to the fixed electrode changes in accordance with the acceleration applied to the sensor device, and outputting a voltage corresponding to the change in the distance between the fixed electrode and the variable electrode as the acceleration signal.

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