JP7164323B2 - Semiconductor devices, ultrasonic sensors, and mobile objects - Google Patents

Description

The present invention relates to technology for improving the performance of ultrasonic sensors.

Ultrasonic sensors that detect the presence or absence of an object and the distance to the object by transmitting an output wave signal in the ultrasonic range and receiving the reflected wave signal have been put to practical use.

As an example of conventional technology related to the above, Patent Document 1 can be cited.

JP 2015-55599 A (paragraph 0043)

Generally, in an ultrasonic sensor, the vibration of the piezoelectric element continues for a certain period of time even after the supply of the burst wave to the piezoelectric element is finished. This fixed period of time is commonly referred to as reverberation time.

Due to the above-described reverberation time, conventional ultrasonic sensors cannot detect the presence or absence of an object (short-range object) located near the sensor and the distance to the short-range object.

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to provide a semiconductor device capable of improving short-range detection performance of an ultrasonic sensor, an ultrasonic sensor including the same, and a mobile object.

In order to achieve the above object, a semiconductor device according to the present invention comprises: a burst signal generation unit that generates a burst signal and supplies the burst signal to a transmission unit that drives a piezoelectric element; and a reset unit for forcibly resetting a filter in the signal processing unit (first configuration).

Further, in the semiconductor device having the first configuration, the configuration (the second configuration) in which the detection of the object based on the received signal is started immediately after the reset unit forcibly resets the filter. good.

Further, in the semiconductor device having the first or second configuration, the reset unit forcibly resets the filter after a predetermined time has passed from the start timing of generation of the burst wave included in the burst signal (the first 3 configuration).

Further, in the semiconductor device having the third configuration, the reset section varies the predetermined time according to an output signal of a temperature sensor provided inside the semiconductor device or near the semiconductor device (fourth configuration). configuration).

Further, in the semiconductor device having the fourth structure, the temperature sensor may be provided (fifth structure).

Further, in the semiconductor device having the first or second configuration, the signal processing unit processes the received signal to generate a signal to be compared with a threshold value used in detecting an object based on the received signal. and the reset unit forcibly resets the filter when a signal to be compared with a threshold value used in detecting an object based on the received signal drops to a predetermined value (sixth configuration), good too.

Further, in the semiconductor device having the sixth configuration, the predetermined value is 40% to 70% of the maximum value of the signal to be compared with a threshold value used in detecting an object based on the received signal (the 7 configuration).

Further, in the semiconductor device having any one of the first to seventh configurations, immediately after the reset unit forcibly resets the filter, detection of an object based on the received signal can be performed in a state of maximum reduction. A configuration (eighth configuration) in which the threshold to be used is decreased may be employed.

In the semiconductor device having any one of the first to eighth configurations, the semiconductor device is a rectangular semiconductor package when viewed from the bottom, and the input terminal for inputting the reception signal and the analog ground terminal are rectangular. It may be arranged in the center of the first side (ninth configuration).

Further, in the semiconductor device having any one of the first to ninth configurations, the semiconductor device is a rectangular semiconductor package when viewed from the bottom, and the terminal for driving the piezoelectric element and the terminal for communication with the outside are connected to the It may be arranged in the center of the second side of the rectangle and arranged between two terminals respectively connected to the ground (tenth configuration).

Further, an ultrasonic sensor according to the present invention includes a semiconductor device according to any one of the first to tenth items above, and a piezoelectric element connected to the semiconductor device (an eleventh configuration). do.

Further, the moving object according to the present invention is configured to include the ultrasonic sensor of the eleventh configuration (twelfth configuration).

ADVANTAGE OF THE INVENTION According to this invention, the short-distance detection performance of an ultrasonic sensor can be improved.

Diagram showing an example of the overall configuration of an ultrasonic sensor Schematic bottom view of semiconductor device showing terminal arrangement Schematic bottom view of semiconductor device showing terminal arrangement A diagram showing a configuration example of a transmission unit A diagram showing a configuration example of a signal processing unit Time chart schematically showing the output signal of the signal processing unit (with reset, without object) Time chart schematically showing the output signal of the signal processor (no reset, no object) Time chart schematically showing the output signal of the signal processing unit (with reset, with object) Time chart schematically showing the output signal of the signal processor (without reset, with object) Diagram showing another overall configuration example of an ultrasonic sensor External view of vehicle

<Overall Configuration of Ultrasonic Sensor>
FIG. 1A is a diagram showing an example of the overall configuration of an ultrasonic sensor. The ultrasonic sensor 100 of this configuration example transmits an output wave signal W1 in an ultrasonic range (=inaudible frequency band, generally 20 kHz or higher) toward the outside world, and transmits the reflected wave signal W2. It is a proximity sensor (a type of external sensor) that performs proximity detection and distance measurement of an object 200 by receiving, and has a piezoelectric element 1 , a semiconductor device 2 , and a transmitter 3 . The drive frequency used in the proximity sensor is generally 30-80 kHz. The ultrasonic sensor 100 of this configuration example is used, for example, as a corner sonar or a back sonar at the corner of a bumper of a car (see FIG. 9 to be described later).

The piezoelectric element 1 has a characteristic of generating mechanical displacement (vibration) according to a voltage signal applied across the piezoelectric element 1, and functions as a transmitter of the output wave signal W1. In addition, the piezoelectric element 1 has the characteristic of generating an electromotive force between both ends according to the mechanical displacement (vibration) applied to itself, and functions also as a wave receiver for the reflected wave signal W2. As the material of the piezoelectric element 1, perovskite ceramics (barium titanate, lead titanate, lead zirconate titanate, etc.) can be preferably used. While the drive signal based on the burst signal S0 is being applied to the piezoelectric element 1, the vibration of the ultrasonic transducer of the piezoelectric element 1 continues. is occurring. In addition, the transmitted ultrasonic signal is reflected from the obstacle, and the ultrasonic transducer of the piezoelectric element 1 receives the reflected wave and vibrates, whereby the piezoelectric element 1 receives the ultrasonic signal based on the reflected wave converted to and output.

The semiconductor device 2 is a control body that uses the piezoelectric element 1 and the transmitter 3 to control the transmission operation of the output wave signal W1 and uses the piezoelectric element 1 to control the reception operation of the reflected wave signal W2. The semiconductor device 2 has a burst signal generation section 10 , a signal processing section 20 , a logic section 30 and a reset section 40 . The semiconductor device 2 also has an output terminal DRV, an input terminal IN, and an input/output terminal I/O as means for establishing electrical connection with the outside of the device. One end of the piezoelectric element 1 is connected to the output terminal DRV via the transmission section 3, and one end of the piezoelectric element 1 is directly connected to the input terminal IN. The other end of the piezoelectric element 1 is connected to ground potential. A semiconductor package applied to the semiconductor device 2 is not particularly limited, but FIG. 1B illustrates a case where a QFN (Quad Flat Non-leaded Package) is applied to the semiconductor device 2 . FIG. 1B is a schematic bottom view of the semiconductor device 2 showing terminal arrangement. Twelve terminals are arranged on each of the four sides SD1 to SD4 of the semiconductor device 2 shown in FIG. 1B. Ground pads GP1 to GP4 are arranged at the four corners of the semiconductor device 2 shown in FIG. 1B, respectively, and a ground pad GP5 is arranged at the center of the semiconductor device 2 shown in FIG. 1B. An input terminal IN and a terminal TM1 are provided on the side SD1. Furthermore, the input terminal IN and the terminal TM1 are arranged in the center of the side SD1. A terminal TM1 is a terminal adjacent to the input terminal IN. Terminal TM1 is an analog ground terminal. Another terminal is arranged between the terminal TM1 and the ground pad GP1, and another terminal is arranged between the input terminal IN and the ground pad GP2. An output terminal DRV, an input/output terminal I/O, a terminal TM2, a terminal TM3, and a terminal TM4 are provided on the side SD2. Side SD2 is a side adjacent to side SD1. The terminal TM2 is a terminal adjacent to the output terminal DRV on one side. A terminal TM2 is a driver ground terminal. Adjacent to the other of output terminals DRV is terminal DRV'. A terminal DRV′ is a terminal connected to the other end of the piezoelectric element 1 . In this embodiment, the other end of the piezoelectric element 1 is connected to the terminal DRV', the terminal DRV' is connected to the terminal TM2 inside the semiconductor device 2, and is connected to the ground via the terminal TM2. The driver is the output stage of the burst signal generator 10. FIG. Another terminal is arranged between the terminal TM2 and the ground pad GP2. A terminal TM3 is a terminal adjacent to the input/output terminal I/O. A terminal TM3 is a communication ground terminal. Note that the communication is communication of the logic unit 30 . Another terminal is arranged between the terminal TM3 and the ground pad GP3. Output terminal DRV, input/output terminal I/O, and terminal TM4 are arranged between terminal TM2 and terminal TM3. Furthermore, the terminal TM4 is arranged between the output terminal DRV and the input/output terminal I/O. A terminal TM4 is a terminal for inputting a power supply voltage (for example, a voltage of DC 12 V) used in the semiconductor device 2 . In other words, the terminals RV and DRV' for driving the piezoelectric element 1 and the input/output terminal I/O of the logic section 30 are arranged on the same side SD2 and between the terminals TM2 and TM3 connected to the ground. placed. Also, unlike the present embodiment, the output of the burst signal generator 10 is in a push-pull format, and the signal processor 20 receives positive and negative signals from the piezoelectric element 1, and the logic unit 30 communicates with separate terminals for transmission and reception. is used, as shown in FIG. 1C, the output terminal DRV corresponds to the positive side output terminal, the output terminal DRV' corresponds to the negative side output terminal, and the positive side input terminals INP and A negative side output terminal INN may be provided, and a reception signal input terminal SI and a transmission signal output terminal SO may be provided instead of the input/output terminal I/O.

The burst signal generator 10 generates a burst signal S0 and supplies it to the transmitter 3 . The burst signal S0 is a signal in which burst waves such as pulses, triangular waves, and sine waves appear intermittently. A burst signal S0 is generated based on the carrier wave S1 and the modulated wave S2. That is, the burst signal S0 is an ultrasonic signal intermittently generated by cutting out the carrier wave S1 at intervals of the modulated wave signal S2. The burst signal S0 has, for example, four voltage peaks, ie four waves, as shown in FIG. 1A. Such a condition is expressed as a burst wavenumber of 4 waves. The carrier wave S1 has a so-called ultrasonic wave, a high frequency which is inaudible to the human ear, for example, above 20 kHz. The frequency of the carrier wave S1 used in this embodiment is, for example, 40 kHz to 80 kHz. The modulated wave S2 is a signal that modulates the carrier wave S1, and its frequency is, for example, several tens of Hz, which is about two digits smaller than the frequency of the carrier wave S1. Note that the "burst wave" refers to the signal component of the carrier wave S1 that forms part of the burst signal S0. Upon receiving the burst signal S0 from the burst signal generator 10, the transmitter 3 drives the piezoelectric element 1 based on the burst signal S0. As a result, the piezoelectric element 1 outputs an output wave signal W1.

The signal processing unit 20 processes the received signal received by the piezoelectric element 1 . The received signal also includes the ultrasonic signal component of the burst signal S0 transmitted from the transmitter 3. FIG. Also, in the present embodiment, one end of the piezoelectric element 1 is directly connected to the input terminal IN, but a receiver may be provided between one end of the piezoelectric element 1 and the input terminal IN. The receiving unit receives an ultrasonic signal converted by the vibration of the ultrasonic transducer of the piezoelectric element 1 and transmits the ultrasonic signal to the signal processing unit 20 . The receiving section may also have a function of cutting a DC signal component and greatly attenuating a high frequency signal. By providing the receiving section, the receiving section transmits an ultrasonic signal determined by the entire transmitting/receiving section to the subsequent circuit section even if the electrical characteristics of the transmitting section 3 and the piezoelectric element 1 are temporarily changed. be able to. As a result, the signal processing in the signal processing unit 20 can be properly executed according to changes in the usage environment of the ultrasonic sensor.

Thus, in this configuration example, a single piezoelectric element 1 is externally connected to the semiconductor device 2, and this piezoelectric element 1 is shared by both the transmitting section 3 and the signal processing section 20 as a transducer. . In other words, the piezoelectric element 1 is used for both transmission and reception of ultrasonic signals.

However, if a piezoelectric element other than the piezoelectric element 1 is externally connected to the semiconductor device 2, the wave transmitter and the wave receiver can be separately prepared. Alternatively, if there is no such need and priority should be given to reducing the number of external terminals, the transmission unit 3 is incorporated in the semiconductor device 2, the output terminal object DRV and the input terminal IN are integrated as input/output terminals, and the semiconductor device 2 , both the transmission unit 3 and the signal processing unit 20 may be connected in parallel to the input/output terminal.

The logic unit 30 is the main body that controls the transmitting unit 10 and the receiving unit 20 when detecting the approach of the object 200 and measuring the distance (=detecting whether or not there is an obstacle in the vicinity).

A reset unit 40 forcibly resets the filter in the signal processing unit 20 .

It should be noted that the approach detection result and the distance measurement result of the object 200 obtained by the ultrasonic sensor 100 may be sequentially output to an arithmetic processing unit (CPU [central processing unit], etc.) serving as a host, or The result may be stored in the illustrated register and read out from the arithmetic processing unit at an arbitrary timing.

<Transmitter>
FIG. 2 is a diagram showing a configuration example of the transmission unit 3. As shown in FIG. The transmitter 3 boosts the burst signal S0 to a sufficient magnitude so that the piezoelectric element 1 is sufficiently driven and vibrated. The boost level is, for example, 80Vpp. The transmission unit 3 of this configuration example includes a transformer 3A, a current source 3B, and a switch 3C.

The transformer 3A includes a primary winding L1 and a secondary winding L2 that are electromagnetically coupled to each other, and drives the piezoelectric element 1 connected across the secondary winding L2 according to the drive current Id flowing through the primary winding L1. do. Thus, by using the transformer 3A as the amplifying means of the transmitter 3, even if the power supply voltage supplied to the transmitter 3 is not so high, the piezoelectric element 1 can be sufficiently driven. It is possible to increase the element voltage V1 (=the voltage applied across the piezoelectric element 1).

The current source 3B is connected between the switch 3C and the ground terminal and generates a predetermined drive current Id.

The switch 3C is connected between the primary winding L1 of the transformer 3A and the current source 3B, and turns on/off the driving current Id (=current flowing through the driving current Id in the example of this figure) according to the burst signal. path conduction/cutoff).

<Signal processing unit>
FIG. 3 is a diagram showing a configuration example of the signal processing unit 20. As shown in FIG. The signal processing unit 20 of this configuration example includes an amplifier 20A, an AD [analog-to-digital] converter 20B, a bandpass filter 20C, and a lowpass filter 20D.

The amplifier 20A amplifies the piezoelectric element voltage V1 (=corresponding to the input wave signal) to generate an amplified output signal AMPO. As the amplifier 20A, a PGA [programmable gain amplifier] or the like, which can arbitrarily adjust its gain, can be preferably used. The voltage amplification degree of the amplifier 20A is appropriately set within a range of 20 dB to 100 dB, for example, based on the magnitude of the received signal.

The AD converter 20B operates at a predetermined sampling frequency (for example, 1 MHz) to convert the analog amplified output signal AMPO into a digital output signal DO. Note that when the ultrasonic signal is analog-processed by the signal processing unit 20, the AD converter 20B and the bandpass filter 20C are not required.

The bandpass filter 20C is a digital filter that limits the band of the digital output signal DO, and the lowpass filter 20D is a digital filter that removes high frequency components of the output signal BO of the bandpass filter 20C. The output signal LO of the low-pass filter 20D (=the output signal of the signal processing section 20) is compared with the threshold in the logic section 30. FIG. The logic unit 30 performs approach detection and distance measurement of the object 200 based on the result of comparison between the output signal LO of the low-pass filter 20D and the threshold.

<Reset section>
The reset unit 40 of this embodiment forcibly resets the band-pass filter 20C after a predetermined time has elapsed from the start timing of generation of the burst wave included in the burst signal. When the bandpass filter 20C is reset, the output signal of the bandpass filter 20C is also reset.

The burst signal generation section 10 generates burst signals under the control of the logic section 30 . Therefore, the logic unit 30 grasps the generation start timing of the burst wave included in the burst signal. Therefore, in the present embodiment, the reset section 40 receives from the logic section 30 information about the burst wave generation start timing included in the burst signal.

The appropriate value of the predetermined time described above differs from ultrasonic sensor 100 to ultrasonic sensor 100 depending on the characteristic variation of each ultrasonic sensor 100 . Therefore, the appropriate value for the predetermined time period described above for each of the ultrasonic sensors 100 may be obtained by an evaluation test or the like, and the appropriate value may be stored in the non-volatile memory (not shown) within the reset unit 40 . Data writing to this nonvolatile memory may be performed via the logic unit 30, for example.

The above-mentioned appropriate value of the predetermined time may be the time from the timing when the burst wave included in the burst signal starts to occur to the timing when the output signal of the signal processing unit 20 starts to decrease during the reverberation time.

The timing at which the output signal of the signal processing unit 20 begins to decrease during the reverberation time is, for example, the timing at which the value of the output signal of the signal processing unit 20 falls within 40% to 70% of the maximum value of the output signal of the signal processing unit 20. It is desirable to When the bandpass filter 20C is reset when the value of the output signal of the signal processing unit 20 is greater than 70% of the maximum value of the output signal of the signal processing unit 20, the reverberation signal and the reflected wave are generated after resetting the bandpass filter 20C. If the band-pass filter 20C is reset when the value of the output signal of the signal processing unit 20 is smaller than 40% of the maximum value of the output signal of the signal processing unit 20, the signal may not be distinguished from the signal. This is because little improvement in short-distance detection performance of the sound wave sensor 100 is expected. More preferably, the timing at which the value of the output signal of the signal processing section 20 becomes approximately 50% of the maximum value of the output signal of the signal processing section 20 should coincide with the timing at which the output signal of the signal processing section 20 is about to become smaller during the reverberation time. Just do it.

4 to 7 are time charts schematically showing output signals of the signal processing section 20. FIG.

FIG. 4 is a time chart when there is no object 200 that reflects the output wave signal W1 while the reset unit 40 is operating. FIG. 5 is a time chart when there is no object 200 that reflects the output wave signal W1 in a state (comparative example) in which the reset unit 40 is not operated.

FIG. 6 is a time chart when an object 200 reflecting the output wave signal W1 exists near the ultrasonic sensor 100 while the reset unit 40 is operating. FIG. 7 is a time chart when an object 200 reflecting the output wave signal W1 exists near the ultrasonic sensor 100 in a state (comparative example) in which the reset unit 40 is not operated.

MAX in FIGS. 4 to 7 indicates the maximum value of the output signal of the signal processing section 20. FIG. R in FIGS. 4 and 6 indicates the timing at which the reset unit 40 resets the bandpass filter 20C.

T1 in FIGS. 4 to 7 indicates the time during which burst waves are generated, and T2 in FIGS. 4 to 7 indicates the reverberation time.

The dashed-dotted lines in FIGS. 4 to 7 indicate thresholds that are compared with the output signal of the signal processing section 20 in the logic section 30. FIG. Data on the threshold is stored in the logic unit 30 in a non-volatile manner.

The threshold is set so as to become smaller step by step as time elapses from the start of generation of the burst wave contained in the burst signal. The object 200 detected by the ultrasonic sensor 100 moves away from the ultrasonic sensor 100 as time passes from the start of generation of the burst wave included in the burst signal, and the reflected wave signal W2 reaching the ultrasonic sensor 100 is attenuated. Note that, unlike the present embodiment, the threshold may be smoothly decreased as time passes from the start of generation of the burst wave included in the burst signal.

ΔMAX in FIGS. 4 to 7 indicates the maximum decrease width of the threshold. In this embodiment, immediately after the reset unit 40 forcibly resets the band-pass filter 20C, the logic unit 30 decreases the threshold value while maximizing the width of decrease. That is, in this embodiment, the threshold is decreased by the maximum decrease width ΔMAX immediately after the reset unit 40 forcibly resets the bandpass filter 20C. As a result, the ultrasonic sensor 100 can appropriately detect the object 200 even when the object 200 existing near the ultrasonic sensor 100 reflects the output wave signal W1 with a low reflectance.

By resetting the bandpass filter 20C by the reset unit 40, the presence or absence of the object 200 and the distance to the object 200 can be detected immediately after the bandpass filter 20C is reset (see FIGS. 4 and 6). In other words, resetting the bandpass filter 20C by the reset unit 40 improves the short-range detection performance of the ultrasonic sensor 100 .

Since the ultrasonic sensor 100 can detect the presence or absence of the object 200 and the distance to the object 200 immediately after resetting the bandpass filter 20C, the logic unit 30 controls the signal processing unit 20 immediately after resetting the bandpass filter 20C. Detection of the object 200 based on the output signal may be started. By preventing detection of the object 200 based on the output signal of the signal processing unit 20 until the bandpass filter 20C is reset, erroneous detection of the object 200 can be prevented.

On the other hand, unless the reset unit 40 resets the bandpass filter 20C as in the comparative example, the reverberation signal and the reflected wave signal cannot be distinguished until the reverberation signal becomes considerably small (see FIGS. 5 and 7). That is, if the reset unit 40 does not reset the bandpass filter 20C as in the comparative example, the presence or absence of the short-range object and the distance to the short-range object cannot be detected due to the reverberation time.

<Another overall configuration of the ultrasonic sensor>
The reverberation signal included in the output signal of the signal processing section 20 has temperature characteristics. Considering the temperature characteristics of this reverberation signal, the ultrasonic sensor 100 may be configured as shown in FIG.

The ultrasonic sensor 100 shown in FIG. 8 has a configuration in which a temperature sensor 50 is added to the ultrasonic sensor 100 shown in FIG. 1A. Temperature sensor 50 is provided inside semiconductor device 2 . As the temperature sensor 50, for example, a temperature detection circuit that detects temperature using the temperature characteristics of a semiconductor element can be used. Further, unlike the configuration example shown in FIG. 8, a temperature sensor may be arranged outside and near the semiconductor device 2 so that the semiconductor device 2 receives the output of the temperature sensor. A thermocouple, for example, can be used as the temperature sensor arranged outside the semiconductor device 2 and in the vicinity of the semiconductor device 2 .

In the ultrasonic sensor 100 shown in FIG. 8, the non-volatile memory (not shown) in the reset unit 40 stores table data indicating the relationship between the appropriate value for the predetermined time and the temperature detected by the temperature sensor 50, or A relational expression indicating the relationship between the proper value of the predetermined time and the temperature detected by the temperature sensor 50 is stored, and the reset unit uses the proper value of the predetermined time according to the temperature detected by the temperature sensor 50. 40 resets the bandpass filter 20C. As a result, in the ultrasonic sensor 100 shown in FIG. 8, even if the temperature condition changes, improvement in short-distance detection performance is not hindered.

Note that the reverberation signal included in the output signal of the signal processing unit 20 may have temporal characteristics. Instead of or in addition to the temperature characteristics of the reverberation signal, the temporal characteristics of the reverberation signal may also be considered.

The temporal characteristics of the reverberation signal are obtained through experiments and simulations. A non-volatile memory (not shown) in the reset unit 40 stores table data indicating the relationship between the appropriate value of the predetermined time and the elapsed time from the completion of manufacture of the ultrasonic sensor 100 or the accumulated usage time of the ultrasonic sensor 100. Alternatively, a relational expression representing the relationship between the appropriate value of the predetermined time and the elapsed time from the completion of manufacture of the ultrasonic sensor 100 or the accumulated usage time of the ultrasonic sensor 100 is stored. Then, it is reset using an appropriate value of a predetermined time according to the elapsed time from the completion of manufacture of the ultrasonic sensor 100 or the cumulative usage time of the ultrasonic sensor 100 measured by a timer or the like provided in the signal processing unit 20. A unit 40 resets the bandpass filter 20C.

Whether to use the elapsed time from the completion of manufacture of the ultrasonic sensor 100 or the accumulated operating time of the ultrasonic sensor 100 may be determined by referring to the results of experiments and simulations regarding the temporal characteristics of reverberation signals.

<Vehicle Sonar>
FIG. 9 is an external view of the vehicle. A front bumper of the vehicle X is provided with front sonars X1 (L, R, C) at the left and right corners and the center thereof. In addition, back sonar X2 (L, R, C) is provided at each of the left and right corners and the center of the rear bumper of vehicle X (however, back sonar X2R and X2C are not shown for convenience of illustration). .

Thus, by mounting the front sonar X1 (L, R, C) and the back sonar X2 (L, R, C) on the vehicle X, objects (=obstacles, other vehicles, or Passers-by, etc.) can be detected and the distance can be measured, so it is possible to support safe driving for drivers.

As the front sonar X1 (L, R, C) and the back sonar X2 (L, R, C), the ultrasonic sensor 100 described above can be applied.

<Other Modifications>
In the above embodiment, the band-pass filter 20C is forcibly reset by the reset unit 40 after a predetermined time has elapsed from the start timing of generation of the burst wave included in the burst signal. When it drops, the reset unit 40 may forcibly reset the bandpass filter 20C.

For example, the logic unit 30 may determine whether or not the output signal of the signal processing unit 20 has decreased to a predetermined value, and the reset unit 40 may receive the determination result from the logic unit 30 . This predetermined value is preferably within 40% to 70% of the maximum value of the output signal of the signal processing section 20, and more preferably approximately 50% of the maximum value of the output signal of the signal processing section 20.

When the band-pass filter 20C is forcibly reset by the reset unit 40 when the output signal of the signal processing unit 20 drops to a predetermined value, the temperature characteristic of the reverberation signal can be obtained without using a temperature sensor, a timer, or the like. Also, the band-pass filter 20C can be reset according to the characteristics over time.

Further, in the above-described embodiment, an example in which the ultrasonic sensor 100 is applied as a vehicle sonar was given, but the application target of the ultrasonic sensor 100 is not limited to this. It may be mounted on a moving object (for example, a drone).

Also, the ultrasonic sensor 100 may be mounted on a stationary object instead of a mobile object. Therefore, the ultrasonic sensor 100 is, for example, a parking management system in which the ultrasonic sensor 100 is provided for each parking space, a humidity sensor, a snow depth gauge, an object detector for a belt conveyor, a liquid level detector when filling a tank, an automatic It can be widely applied to human body sensors such as doors and intrusion monitoring devices, or various displacement measuring instruments.

In this way, the various technical features disclosed in this specification can be modified in various ways in addition to the above-described embodiments without departing from the gist of the technical creation. That is, the above-described embodiments should be considered as examples and not restrictive in all respects, and the technical scope of the present invention is indicated by the scope of claims rather than the description of the above-described embodiments. It should be understood that all changes that fall within the meaning and range of equivalence to the claims are included.

The ultrasonic sensor disclosed in this specification can be used, for example, as an external sensor for a vehicle.

REFERENCE SIGNS LIST 1 piezoelectric element 2 semiconductor device 3 transmission section 3A transformer 3B current source 3C switch 10 burst signal generation section 20 signal processing section 20A amplifier 20B AD converter 20C bandpass filter 20D lowpass filter 30 logic section 40 reset section 50 temperature sensor 100 ultrasonic sensor 200 Object X Vehicle X1 (L, R, C) Front sonar X2 (L, R, C) Back sonar

Claims (8)

a burst signal generator that generates a burst signal and supplies the burst signal to a transmitter that drives a piezoelectric element;
a signal processing unit that processes a received signal received by the piezoelectric element or another piezoelectric element;
a reset unit for resetting a filter in the signal processing unit;
A semiconductor device comprising
the filter is a digital filter that limits the frequency band of the signal supplied to the filter;
The reset unit resets the filter after a predetermined time has elapsed from the start timing of generation of the burst wave included in the burst signal,
The semiconductor device, wherein the reset section varies the predetermined time according to an output signal of a temperature sensor provided inside or near the semiconductor device. 2. The semiconductor device according to claim 1, wherein immediately after said reset unit resets said filter, detection of an object based on said received signal is started. 3. The semiconductor device according to claim 1, comprising said temperature sensor. 4. The semiconductor device according to claim 1, wherein immediately after said reset unit resets said filter, a threshold value used for detection of an object based on said received signal is decreased with a maximum decrease width. . 5. The semiconductor device according to any one of claims 1 to 4, wherein said semiconductor device is a rectangular semiconductor package when viewed from below, and said input terminal for inputting said reception signal and said analog ground terminal are arranged in the center of said first side of said rectangle. 1. The semiconductor device according to item 1. The semiconductor device is a rectangular semiconductor package when viewed from the bottom, and a terminal for driving the piezoelectric element and a terminal for communication with the outside are arranged at the center of the second side of the rectangle and are connected to the ground. 6. The semiconductor device according to any one of claims 1 to 5, wherein the semiconductor device is arranged between two terminals of the terminal. A semiconductor device according to any one of claims 1 to 6;
a piezoelectric element connected to the semiconductor device;
an ultrasonic sensor. A moving object comprising the ultrasonic sensor according to claim 7 .

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