JP2017050664A - Analog reference voltage generating circuit, circuit device, physical quantity sensor, electronic device and moving object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an analog reference voltage generating circuit capable of reducing noise due to an analog reference voltage in a ratiometric circuit, a circuit device, a physical quantity sensor, an electronic device, a moving object and the like.SOLUTION: An analog reference voltage generating circuit 300 includes: a voltage dividing circuit 310 that divides the power supply voltage to output a divided voltage VB; an AC component extracting circuit 340 that extracts an AC component from a first signal SB1 which is a signal based on the divided voltage VB; and a subtraction circuit 350 that performs a subtraction between a second signal SB2 which is a signal based on the divided voltage VB and an output signal SAC from an AC component extracting circuit 340 to output an analog reference voltage VRF for an analog circuit.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an analog reference voltage generation circuit, a circuit device, a physical quantity sensor, an electronic device, a moving object, and the like.

  A circuit that varies the analog reference voltage in proportion to the fluctuation of the power supply voltage and performs signal processing using the analog reference voltage is called a ratiometric circuit. For example, it is assumed that an A / D conversion circuit is provided in the subsequent stage of an amplifier circuit that processes signals, and output data of the A / D conversion circuit depends on an analog reference voltage that varies according to a power supply voltage. In this case, an error in the output data of the A / D conversion circuit is suppressed by performing signal processing with the analog reference voltage that varies according to the power supply voltage as a reference also in the amplifier circuit in the previous stage. Such a ratiometric circuit is disclosed in Patent Document 1, for example.

JP 2008-175805 A

  As described above, in the ratiometric circuit, the analog reference voltage fluctuates according to the fluctuation of the power supply voltage, so that the noise of the power supply voltage propagates as the noise of the analog reference voltage. When signal processing (for example, multistage amplification, etc.) is performed using an analog reference voltage with such noise, the noise of the analog reference voltage affects the signal and lowers the S / N of the signal. There is.

  For example, in Patent Document 1, noise in the output signal of the gyro sensor is reduced by a filter circuit. However, when a filter circuit is inserted in the signal processing path, noise within the signal band (for example, a band equal to or lower than the cutoff frequency of the low-pass filter) cannot be reduced. For this reason, noise caused by the noise of the analog reference voltage appears in the output signal of the gyro sensor.

  According to some aspects of the present invention, it is possible to provide an analog reference voltage generation circuit, a circuit device, a physical quantity sensor, an electronic device, a moving body, and the like that can reduce noise of an analog reference voltage in a ratiometric circuit.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or modes.

  One aspect of the present invention is a voltage dividing circuit that divides a power supply voltage and outputs a divided voltage, an AC component extraction circuit that extracts an AC component of a first signal that is a signal based on the divided voltage, The present invention relates to an analog reference voltage generation circuit including a second signal that is a signal based on a divided voltage and a subtraction circuit that outputs an analog reference voltage by performing a subtraction process on the output signal of the AC component extraction circuit.

  According to one aspect of the present invention, a subtraction process is performed between a second signal that is a signal based on a divided voltage and an AC component signal extracted from the first signal that is a signal based on a divided voltage. The signal obtained by the subtraction process is output as an analog reference voltage. As a result, an analog reference voltage with reduced alternating current components can be output, so that noise of the analog reference voltage in the ratiometric circuit can be reduced.

  In one embodiment of the present invention, the analog reference voltage generation circuit includes the first buffer circuit that receives the divided voltage and outputs the first signal having a voltage corresponding to the divided voltage, and the divided voltage. A second buffer circuit that receives a voltage and outputs the second signal having a voltage corresponding to the divided voltage.

  When a current flows from the voltage dividing circuit to the subsequent circuit, the current flows through the voltage dividing circuit, and an error occurs in the divided voltage. In this regard, according to one aspect of the present invention, by providing the first buffer circuit and the second buffer circuit, the voltage dividing circuit and the subsequent circuit can be separated by impedance conversion. Can be reduced.

  In the aspect of the invention, the AC component extraction circuit may include a high-pass filter that receives the first signal and extracts an AC component of the first signal.

  By including the high-pass filter in the AC component extraction circuit, the AC component can be extracted by removing the DC component from the first signal that is a signal based on the divided voltage.

  In the aspect of the invention, the AC component extraction circuit includes a first operational amplifier in which an output signal of the high-pass filter is input to a first input node, and a second input node of the first operational amplifier. And a first resistance element provided between the first operational amplifier and an output node of the first operational amplifier, and provided between the second input node of the first operational amplifier and the node of the low-potential side power supply voltage. And a second resistance element.

  The first operational amplifier, the first resistance element, and the second resistance element constitute a so-called forward amplifier. And by amplifying the output signal of the high-pass filter with a non-inverting amplifier, it is possible to adjust the gain of the AC component and extract the AC component with an appropriate gain to subtract the AC component from the analog reference voltage Become.

  In one embodiment of the present invention, the subtracting circuit is provided between a second operational amplifier, a node to which the second signal is input, and a first input node of the second operational amplifier. 3 resistance elements, a fourth resistance element provided between the first input node of the second operational amplifier and the node of the low potential side power supply voltage, the output node of the AC component extraction circuit, and the A fifth resistance element provided between the second operational amplifier and a second input node of the second operational amplifier; and a second input node of the second operational amplifier and an output node of the second operational amplifier. And a sixth resistance element provided.

  The second operational amplifier and the third to sixth resistance elements constitute a single-ended output amplifier circuit with a differential input. Then, by obtaining the difference between the differential inputs by this amplifier circuit, it is possible to realize a subtraction process between the second signal that is a signal based on the divided voltage and the output signal of the AC component extraction circuit.

  In one aspect of the present invention, the analog reference voltage generation circuit may include a low-pass filter that outputs the analog reference voltage from the subtraction circuit by low-pass filtering.

  At a frequency higher than the band of the operational amplifier included in the subtracting circuit, the gain of the feedback loop of the subtracting circuit is reduced (or the phase is turned), so that part of the noise passes. In this regard, according to one aspect of the present invention, it is possible to reduce noise over a higher frequency band by providing a low-pass filter in the subsequent stage of the subtraction circuit.

  According to another aspect of the present invention, the analog reference voltage generation circuit according to any one of the above, an amplifier circuit in which the analog reference voltage from the analog reference voltage generation circuit is input to an analog reference voltage input node, Relates to a circuit device including

  According to another aspect of the present invention, the analog reference voltage whose noise is reduced by the analog reference voltage generation circuit is input to the amplifier circuit of the circuit device. Thereby, in the signal which the analog circuit contained in a circuit apparatus processes, the S / N fall resulting from the noise of an analog reference voltage can be suppressed.

  According to another aspect of the present invention, there is provided the analog reference voltage generation circuit according to any one of the above, and an amplifier circuit in which the analog reference voltage from the analog reference voltage generation circuit is input to an analog reference voltage input node. And a detection circuit that outputs physical quantity information corresponding to the physical quantity based on a detection signal corresponding to the physical quantity output from the physical quantity transducer.

  According to another aspect of the present invention, the analog reference voltage from the analog reference voltage generation circuit is supplied to the detection circuit that detects the physical quantity based on the detection signal from the physical quantity transducer. Thereby, even when noise is superimposed on the power supply line of the circuit device, the physical quantity can be detected while reducing the influence thereof, so that the detection accuracy of the physical quantity can be improved.

  In another aspect of the invention, the amplifier circuit is included in at least one of a charge-voltage conversion circuit, a differential amplifier circuit, a sensitivity adjustment circuit, an offset adjustment circuit, a synchronous detection circuit, and a filter circuit of the detection circuit. An amplifier circuit may be used.

  Thus, since the detection circuit includes a multi-stage amplifier circuit, noise propagated from the analog reference voltage to the output of the amplifier circuit at each stage is amplified by the subsequent amplifier circuit. In this regard, according to another aspect of the present invention, since the noise of the analog reference voltage is reduced, the noise can be effectively reduced in such a multistage amplifier circuit.

  Another aspect of the present invention relates to a physical quantity sensor including any one of the circuit devices described above and the physical quantity transducer.

  Another aspect of the invention relates to an electronic device including the circuit device described in any of the above.

  Another aspect of the present invention relates to a moving body including the circuit device described in any of the above.

An example of a ratiometric circuit. The comparative example of an analog reference voltage generation circuit. 1 is a first configuration example of an analog reference voltage generation circuit according to an embodiment. 5 is a waveform example in the analog reference voltage generation circuit of the present embodiment. 2 shows a second configuration example of an analog reference voltage generation circuit according to the present embodiment. The schematic diagram of the gain frequency characteristic of an operational amplifier and a low-pass filter. The detailed structural example of an electronic device, a gyro sensor, and a circuit device. 3 shows a detailed configuration example of a drive circuit and a detection circuit of a circuit device. Examples of mobile objects and electronic devices.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are indispensable as means for solving the present invention. Not necessarily.

1. Ratiometric Circuit FIG. 1 shows an example of a ratiometric circuit. The ratiometric circuit of FIG. 1 includes an analog reference voltage generation circuit 300 and an amplification circuit 400. Note that the ratiometric circuit is not limited to this configuration, and may be any circuit that performs signal processing using an analog reference voltage that varies according to variations in the power supply voltage. The ratiometric circuit may change the amplitude (amplification gain) of the signal in accordance with the fluctuation of the power supply voltage. In this embodiment, a case in which the analog reference voltage is changed in accordance with the fluctuation of the power supply voltage will be described.

  The analog reference voltage generation circuit 300 divides between the high potential side power supply voltage VDD and the low potential side power supply voltage VSS and outputs an analog reference voltage VRF (analog ground). When the voltage division ratio is α, VRF = α × (VDD−VSS) + VSS, and when VSS = 0, VRF = α × VDD.

  In FIG. 1, a differential input and single-ended output amplifier circuit is illustrated as an example of the amplifier circuit 400. When the differential input voltages of the amplifier circuit 400 are VI1 and VI2 and the gain is G, the output voltage VQ is expressed by the formula FA. As can be seen from the formula FA, a signal G × (VI2-VI1) based on the analog reference voltage VRF is output as the output voltage VQ.

  As described above, the signal processing performed by the ratiometric circuit is, for example, processing for generating a signal based on the analog reference voltage VRF. Alternatively, a process of multiplying the difference between the input voltage and the analog reference voltage VRF by a gain and outputting the result with the analog reference voltage VRF as a reference may be used as in a single-ended input amplifier circuit. Alternatively, in the switched capacitor circuit, the input voltage is sampled with the analog reference voltage VRF as a reference, and the sampling result or the result of amplification or filtering of the sampling result is output with the analog reference voltage VRF as a reference. Good. In addition, analog signal processing or analog / digital conversion processing performed using the analog reference voltage VRF as a reference may be included. In these processes, the analog reference voltage VRF is included in the mathematical expression representing the process result, so that the process result varies when the analog reference voltage VRF varies.

2. Comparative Configuration Example FIG. 2 shows a comparative configuration example of the analog reference voltage generation circuit 300. The analog reference voltage generation circuit 300 in FIG. 2 includes resistance elements RS1 and RS2 connected in series between a node of the high potential side power supply voltage VDD and a node of the low potential side power supply voltage VSS.

  The analog reference voltage generation circuit 300 outputs a divided voltage by the resistance elements RS1 and RS2 as an analog reference voltage VRF. For example, when the resistance values of the resistance elements RS1 and RS2 are the same and VSS = 0, VRF = (1/2) × VDD. At this time, the formula FA of FIG. 1 is VQ = G × (VI2−VI1) + (½) × VDD, and the voltage VQ varies according to the power supply voltage VDD.

  A ratiometric circuit is a power supply such as a difference in power supply voltage VDD due to a difference in power supply (system power supply in which the ratiometric circuit is incorporated) or a change in power supply voltage VDD over time due to a decrease in remaining battery power. This is a circuit for following the fluctuation of the voltage VDD. That is, a difference in the power supply voltage VDD as a direct current voltage (DC voltage) or a very slow change in the power supply voltage VDD is assumed.

  However, due to the nature of changing the analog reference voltage VRF according to the fluctuation of the power supply voltage VDD, for example, when noise as shown in A1 of FIG. 2 is added to the power supply voltage VDD, the analog reference voltage VRF is changed according to the noise. Even noise will occur. When the voltage is halved simply as in the comparative configuration example of FIG. 2, the noise with the noise amplitude of the power supply voltage VDD halved propagates to the analog reference voltage VRF. Such noise of the analog reference voltage VRF is also included in the output signal of the ratiometric circuit, which causes a reduction in the S / N of the output signal of the ratiometric circuit (for example, the measurement accuracy of angular velocity in the gyro sensor). .

  In FIG. 1, the amplifier circuit 400 is one stage, but the ratiometric circuit may be a circuit that performs multistage amplification based on the analog reference voltage VRF. In this case, the analog reference voltage VRF is included in the output signal of each stage, and the noise on the analog reference voltage VRF is also input to the next stage. At this time, since each stage uses the analog reference voltage VRF as a reference, noise is ideally canceled. However, in reality, a change in the noise waveform when passing through the amplifier circuit of each stage, and the analog reference voltage VRF There is a possibility that it is not completely canceled due to a change in the noise waveform due to the parasitic impedance of the wiring. As a result, the noise of the analog reference voltage VRF that has not been canceled is amplified by a multistage gain. Especially when a minute signal is amplified with a high gain (for example, amplification with a detection circuit of a gyro sensor), or when the power supply environment is bad such as in-vehicle use, the noise of the analog reference voltage VRF is a big problem. There is a possibility.

3. Analog Reference Voltage Generation Circuit FIG. 3 shows a first configuration example of an analog reference voltage generation circuit 300 according to this embodiment that can solve the above-described problems. An analog reference voltage generation circuit 300 in FIG. 3 extracts an AC component from a voltage dividing circuit 310 that divides a power supply voltage and outputs a divided voltage VB, and a first signal SB1 that is a signal based on the divided voltage VB. Subtracting the AC component extraction circuit 340, the second signal SB2, which is a signal based on the divided voltage VB, and the output signal SAC of the AC component extraction circuit 340, and outputting the analog reference voltage VRF for the analog circuit A subtracting circuit 350.

  Specifically, voltage dividing circuit 310 includes resistance elements RR1 and RR2. One end of the resistance element RR1 is connected to the node of the high potential side power supply voltage VDD, and the other end is connected to the node NA1. One end of the resistance element RR2 is connected to the node NA1, and the other end is connected to the node of the low potential side power supply voltage VSS. The voltage dividing circuit 310 divides the power supply voltages VDD and VSS by the resistance elements RR1 and RR2, and outputs a divided voltage VB = (RR2 / (RR1 + RR2)) × (VDD−VSS) + VSS.

  The first signal SB1 and the second signal SB2 are signals having the same voltage (including substantially the same) as the divided voltage VB. For example, a signal obtained by impedance conversion of the divided voltage VB may be used, or the divided voltage VB itself may be used.

  The AC component extraction circuit 340 cuts the DC component of the first signal SB1 and passes the AC component. The lower limit of the band of the AC component to be passed is arbitrary. For example, when the analog reference voltage VRF is supplied to the detection circuit of the gyro sensor, the upper limit of the band of the output signal of the detection circuit (the cutoff frequency of the low-pass filter) It may be low. Alternatively, when digital processing is performed after A / D converting the output signal of the detection circuit, it may be lower than the upper limit of the band of the output signal of the processing unit (cut-off frequency of the low-pass filter).

  The subtraction circuit 350 subtracts a signal SAC that is an AC component of the first signal SB from the second signal SB2. This corresponds to reducing (or removing) the AC component of the divided voltage VB from the divided voltage VB. The lower limit of the AC component band to be reduced corresponds to the lower limit of the AC component band that the AC component extraction circuit 340 passes.

  According to the above configuration, the divided voltage VB in which the AC component is reduced can be output as the analog reference voltage VRF. Accordingly, it is possible to realize a ratiometric function for outputting the analog reference voltage VRF proportional to the power supply voltage while suppressing the noise component of the power supply voltage from propagating to the analog reference voltage VRF. Further, the AC component can be effectively reduced by using a method of subtracting the AC component from the divided voltage VB. For example, when a low-pass filter is applied to the divided voltage VB, the gain gradually decreases as the frequency becomes higher than the cutoff frequency. Therefore, there is a possibility that an AC component remains to some extent even at a frequency higher than the cutoff frequency. On the other hand, when the extracted AC component is subtracted from the divided voltage VB, it is possible to substantially remove the AC component at a frequency higher than the cutoff frequency of AC component extraction.

  The analog reference voltage generation circuit 300 according to the present embodiment receives the divided voltage VB (receives the divided voltage VB) and outputs a first signal SB1 having a voltage corresponding to the divided voltage VB. The buffer circuit 320 includes a second buffer circuit 330 that receives the divided voltage VB (receives the divided voltage VB) and outputs a second signal SB2 having a voltage corresponding to the divided voltage VB.

  Specifically, the first buffer circuit 320 includes an operational amplifier OP3 whose positive input terminal (first input terminal, first input node) is connected to the node NA1. A negative input terminal (second input terminal, second input node) and an output terminal (output node) of the operational amplifier OP3 are connected to the node NA2. That is, the first buffer circuit 320 is a so-called voltage follower, and buffers the divided voltage VB and outputs the same voltage as the divided voltage VB (for example, an error such as an offset voltage may be included).

  The second buffer circuit 330 includes an operational amplifier OP4 whose positive input terminal (first input terminal, first input node) is connected to the node NA1. The negative input terminal (second input terminal, second input node) and output terminal (output node) of the operational amplifier OP4 are connected to the node NA3. That is, the second buffer circuit 330 is a so-called voltage follower, and buffers the divided voltage VB and outputs the same voltage as the divided voltage VB (for example, an error such as an offset voltage may be included).

  When a current flows from the output node NA1 of the voltage dividing circuit 310 to the subsequent circuit, the current flows through the voltage dividing circuit 310, and an error occurs in the divided voltage VB (interference effect). In this regard, in the present embodiment, the first buffer circuit 320 and the second buffer circuit 330 receive the divided voltage VB with a high input impedance, and the first signal SB1 and the second signal SB2 with a low output impedance. Can be output. Thereby, the voltage dividing circuit 310 and the subsequent circuit can be separated by impedance conversion, and an error of the divided voltage VB can be prevented.

  The AC component extraction circuit 340 includes a high-pass filter 342 that receives the first signal SB1 (receives the first signal SB1) and extracts the AC component of the first signal SB1.

  Specifically, the high pass filter 342 includes a capacitor CAC and a resistance element RAC. One end of the capacitor CAC is connected to the output node NA2 of the first buffer circuit 320, and the other end is connected to the node NA4. One end of the resistor element RAC is connected to the node NA4, and the other end is connected to a node of the low potential side power supply voltage VSS (reference voltage in a broad sense). The high pass filter 342 is a primary passive filter, and outputs a signal SHF in the pass band (a band higher than the cutoff frequency) of the first signal SB1 to the node NA4. Note that the high-pass filter 342 is not limited to this configuration, and may be, for example, a second or higher order filter or an active filter.

  As described above, since the AC component extraction circuit 340 includes the high-pass filter 342, the AC component can be extracted by removing the DC component from the divided voltage VB. Since the gain characteristic of the high-pass filter 342 is 1 at the flat portion of the pass band, the AC component can be effectively removed from the divided voltage VB when the AC component is subtracted by the subtraction circuit 350.

  In addition, the AC component extraction circuit 340 includes a first operational amplifier OP1 in which the output signal SHF of the high pass filter 342 is input to the first input node NA4 (positive input terminal, first input terminal), and a first operational amplifier. The first resistor RA1 provided between the second input node NA5 (negative input terminal, second input terminal) of OP1 and the output node NA6 of the first operational amplifier OP1, and the first operational amplifier OP1 And a second resistance element RA2 provided between the second input node NA5 and a node of the low potential side power supply voltage VSS (reference voltage in a broad sense).

  The operational amplifier OP1 and the resistance elements RA1 and RA2 constitute a so-called normal amplifier, which amplifies the output signal SHF of the high-pass filter 342 and outputs a signal SAC. The gain of the non-inverting amplifier (resistance values of the resistance elements RA1 and RA2) is such that the AC component (noise) can be as much as possible from the analog reference voltage VRF when the subtraction circuit 350 subtracts the AC component signal SAC from the second signal SB2. What is necessary is just to set so that it can remove. For example, a gain for canceling the attenuation in the high pass filter 342 may be set.

  By amplifying the output signal SHF of the high-pass filter 342 in this way, the AC component can be extracted with an appropriate gain in order to remove the AC component from the analog reference voltage VRF. In addition, since the output signal SHF of the high-pass filter 342 can be received by a normal input amplifier having a high input impedance, the AC component can be amplified without affecting the frequency characteristics of the high-pass filter 342 that is a passive filter.

  The subtracting circuit 350 includes a second operational amplifier OP2, a node NA3 to which the second signal SB2 is input, and a first input node NA7 (positive input terminal, first input terminal) of the second operational amplifier OP2. A third resistance element RD1 provided between the first input node NA7 of the second operational amplifier OP2 and a node of the low-potential-side power supply voltage VSS (reference voltage in a broad sense). 4 resistor element RD2, a fifth resistor provided between the output node NA6 of the AC component extraction circuit 340 and the second input node NA8 (negative input terminal, second input terminal) of the second operational amplifier OP2. It includes an element RD3, and a sixth resistance element RD4 provided between the second input node NA8 of the second operational amplifier OP2 and the output node NA9 of the second operational amplifier OP2.

  The operational amplifier OP2 and the resistance elements RD1 to RD4 constitute a so-called analog subtraction circuit (a differential input and single-ended output amplification circuit), which amplifies the difference between the second signal SB2 and the signal SAC. The analog reference voltage VRF is output. The gain of the analog subtracting circuit (the resistance values of the resistance elements RD1 to RD4) is arbitrary. For example, the gain may be set to 1 (RD1 = RD2 = RD3 = RD4).

  Thus, by obtaining the difference between the second signal SB2 and the signal SAC, the AC component of the analog reference voltage VRF can be reduced. This point will be specifically described with reference to FIG. FIG. 4 is a waveform example when the divided voltage is VB = VDD / 2, the gain of the AC component extraction circuit 340 is 1, and the gain of the subtraction circuit 350 is 1. Assume that noise having an amplitude of ± 1% × vd centered on the voltage vd (direct current component of VDD) is added to the power supply voltage VDD as shown in FIG. In this case, the divided voltage VB is obtained by adding a noise of ± 0.5% × vd to a direct current component of 0.5 vd. The output signal SAC of the AC component extraction circuit 340 is a signal having an amplitude of ± 0.5% × vd, which is noise (AC component) of the divided voltage VB, and the DC component is 0V. Since VRF = SB2-SAC and SB2 = VB, VRF = VB-SAC = (0.5 vd ± 0.5% × vd) − (± 0.5% × vd) = 0.5 vd, and the AC component is removed ( An analog reference voltage VRF obtained by extracting a DC component is obtained.

4). Second Configuration Example FIG. 5 shows a second configuration example of the analog reference voltage generation circuit 300 of this embodiment. 5 includes a voltage dividing circuit 310, a first buffer circuit 320, a second buffer circuit 330, an AC component extraction circuit 340, a subtraction circuit 350, and a low-pass filter 360. In addition, the same code | symbol is attached | subjected about the component same as the component demonstrated in the 1st structural example, and description is abbreviate | omitted suitably.

  The low-pass filter 360 performs low-pass filtering on the analog reference voltage VRF ′ from the subtraction circuit 350 and outputs the analog reference voltage VRF after the low-pass filtering.

  Specifically, the low pass filter 360 includes a resistance element RQ and a capacitor CQ. One end of resistance element RQ is connected to output node NA9 of subtraction circuit 350, and the other end is connected to node NA10. One end of the capacitor CQ is connected to the node NA10, and the other end is connected to the node of the low potential side power supply voltage VSS. The low-pass filter 360 is a primary passive filter, and outputs the analog reference voltage VRF subjected to the low-pass filter processing to the node NA10.

  FIG. 6 schematically shows the gain frequency characteristic GCD of the operational amplifier OP2 (or the operational amplifier OP1) and the gain frequency characteristic GCQ of the low-pass filter 360. When the cutoff frequency of the gain frequency characteristic GCD is fcd and the cutoff frequency of the gain frequency characteristic GCQ is fcq, it is desirable that fcd <fcq. Since the low-pass filter 360 is related to the phase compensation (stability) of the feedback loop of the subtraction circuit 350, the influence on the phase compensation (possibility of oscillation) can be reduced by setting fcd <fcq.

  At a frequency higher than the band of the subtraction circuit 350 (cut-off frequency fcd), the gain of the feedback loop of the subtraction circuit 350 decreases (or the phase rotates), so that the subtraction is not performed correctly and noise passes. In this regard, in the present embodiment, by providing the low-pass filter 360 subsequent to the subtracting circuit 350, it is possible to reduce noise that has passed through the subtracting circuit 350. Thereby, the alternating current component (noise) of the analog reference voltage VRF can be reduced over a higher frequency band.

5). FIG. 7 shows a circuit device 20 to which the analog reference voltage generation circuit 300 of this embodiment is applied, and a gyro sensor 510 including the circuit device 20 (physical quantity sensor and physical quantity detection device in a broad sense). A detailed configuration example of the electronic device 500 including the gyro sensor 510 will be described. Hereinafter, a case where the circuit device is a circuit device for angular velocity detection in a gyro sensor will be described as an example. However, the analog reference voltage generation circuit 300 of the present embodiment can be applied to circuit devices for various uses. .

  The circuit device 20, the electronic device 500, and the gyro sensor 510 are not limited to the configuration shown in FIG. 7, and various modifications may be made such as omitting some of the components or adding other components. It is. In addition, as the electronic device 500 of the present embodiment, various devices such as a digital camera, a video camera, a smartphone, a mobile phone, a car navigation system, a robot, a biological information detection device, a game machine, a watch, a health appliance, or a portable information terminal are used. Equipment can be assumed. In the following description, the physical quantity transducer (angular velocity sensor element) is a piezoelectric vibrating piece (vibrating gyro) and the sensor is a gyro sensor. However, the present invention is not limited to this. For example, the present invention can be applied to a capacitance detection type vibration gyro formed from a silicon substrate or the like, a physical quantity equivalent to angular velocity information, or a physical quantity transducer that detects a physical quantity other than angular velocity information.

  Electronic device 500 includes a gyro sensor 510 and a processing unit 520. Further, a memory 530, an operation unit 540, and a display unit 550 can be included. A processing unit 520 (processing device) realized by a CPU, MPU, or the like performs control of the gyro sensor 510 and the like and overall control of the electronic device 500. The processing unit 520 performs processing based on angular velocity information (physical quantity information in a broad sense) detected by the gyro sensor 510. For example, processing for camera shake correction, posture control, GPS autonomous navigation, and the like is performed based on the angular velocity information. The memory 530 (ROM, RAM, etc.) stores control programs and various data, and functions as a work area and a data storage area. The operation unit 540 is for the user to operate the electronic device 500, and the display unit 550 displays various information to the user.

  The gyro sensor 510 includes the resonator element 10, the circuit device 20, and the processing device 110. The vibrating piece 10 (physical quantity transducer or angular velocity sensor element in a broad sense) is a piezoelectric vibrating piece formed from a thin plate of a piezoelectric material such as quartz. Specifically, the vibrating piece 10 is a double T-shaped vibrating piece formed of a Z-cut quartz substrate.

  The circuit device 20 includes a drive circuit 30, a detection circuit 60, an analog reference voltage generation circuit 300, and a control unit 140. The circuit device 20 is realized by a semiconductor integrated circuit device, for example. Various modifications such as omitting some of these components or adding other components are possible.

  The drive circuit 30 outputs a drive signal DQ to drive the resonator element 10. For example, the vibration piece 10 is excited by receiving the feedback signal DI from the vibration piece 10 and outputting the corresponding drive signal DQ. The detection circuit 60 receives the detection signals IQ1 and IQ2 (detection current and charge) from the vibration piece 10 driven by the drive signal DQ, and receives a desired signal corresponding to the physical quantity applied to the vibration piece 10 from the detection signals IQ1 and IQ2. (Coriolis force signal) is detected (extracted). The analog reference voltage generation circuit 300 supplies the analog reference voltage VRF to the detection circuit 60. The control unit 140 performs control processing for the circuit device 20. The control unit 140 can be realized by a logic circuit (gate array or the like), a processor, or the like. Various switch controls, mode settings, and the like in the circuit device 20 are performed by the control unit 140.

  The processing device 110 includes an A / D conversion circuit 112 that converts an analog desired signal detected by the detection circuit 60 into a digital signal. The processing device 110 performs digital signal processing such as digital filter processing and digital correction processing on the digital signal from the A / D conversion circuit 112. Examples of digital correction processing include zero point correction processing and sensitivity correction processing. The processor 110 can use various processors such as a DSP (Digital Signal Processor), and is realized by a semiconductor integrated circuit device, for example. Note that the processing device 110 may be omitted, and the function thereof may be included in the processing unit 520.

  The resonator element 10 includes a base 1, connecting arms 2 and 3, driving arms 4, 5, 6 and 7, and detection arms 8 and 9. The detection arms 8 and 9 extend in the + Y axis direction and the −Y axis direction with respect to the rectangular base 1. Further, the connecting arms 2 and 3 extend in the −X axis direction and the + X axis direction with respect to the base portion 1. The drive arms 4 and 5 extend in the + Y-axis direction and the −Y-axis direction with respect to the connection arm 2, and the drive arms 6 and 7 extend in the + Y-axis direction and the −Y-axis direction with respect to the connection arm 3. ing. The X axis, Y axis, and Z axis indicate the vibration direction.

  The drive signal DQ from the drive circuit 30 is input to the drive electrodes provided on the upper surfaces of the drive arms 4 and 5 and the drive electrodes provided on the side surfaces of the drive arms 6 and 7. In addition, signals from the drive electrodes provided on the side surfaces of the drive arms 4 and 5 and the drive electrodes provided on the upper surfaces of the drive arms 6 and 7 are input to the drive circuit 30 as feedback signals DI. Further, signals from detection electrodes provided on the upper surfaces of the detection arms 8 and 9 are input to the detection circuit 60 as detection signals IQ1 and IQ2. The common electrode provided on the side surfaces of the detection arms 8 and 9 is grounded, for example.

  When an AC drive signal DQ is applied by the drive circuit 30, the drive arms 4, 5, 6, and 7 perform bending vibration (excitation vibration) as indicated by an arrow A due to the inverse piezoelectric effect. That is, the distal ends of the driving arms 4 and 6 repeatedly approach and separate from each other, and the distal ends of the driving arms 5 and 7 also perform bending vibrations that repeatedly approach and separate from each other. At this time, since the driving arms 4 and 5 and the driving arms 6 and 7 are oscillating line-symmetrically with respect to the Y axis passing through the center of gravity of the base 1, the base 1, the connecting arms 2 and 3, and the detection arm 8. , 9 hardly vibrate.

  In this state, when an angular velocity with the Z axis as the rotation axis is applied to the vibrating piece 10 (when the vibrating piece 10 rotates around the Z axis), the drive arms 4, 5, 6, and 7 are moved to the arrow B by Coriolis force. Vibrate as shown. That is, the Coriolis force in the direction of the arrow B perpendicular to the direction of the arrow A and the direction of the Z-axis acts on the drive arms 4, 5, 6, and 7, thereby generating a vibration component in the direction of the arrow B. The vibration of the arrow B is transmitted to the base 1 via the connecting arms 2 and 3, and the detection arms 8 and 9 perform bending vibration in the direction of the arrow C. Charge signals generated by the piezoelectric effect due to the bending vibration of the detection arms 8 and 9 are input to the detection circuit 60 as detection signals IQ1 and IQ2. Here, the vibration of the arrow B of the drive arms 4, 5, 6, and 7 is the vibration in the circumferential direction with respect to the center of gravity of the base portion 1, and the vibration of the detection arms 8 and 9 is It is the vibration in the direction of the arrow C in the opposite direction. The detection signals IQ1 and IQ2 are signals whose phases are shifted by 90 degrees with respect to the drive signal DQ.

  For example, when the angular velocity of the vibrating piece 10 (gyro sensor) around the Z axis is ω, the mass is m, and the vibration velocity is v, the Coriolis force is expressed as Fc = 2 m · v · ω. Therefore, the detection circuit 60 can obtain the angular velocity ω by detecting a desired signal that is a signal corresponding to the Coriolis force. By using the obtained angular velocity ω, the processing unit 520 can perform various processes for camera shake correction, posture control, GPS autonomous navigation, and the like.

  FIG. 7 shows an example in which the resonator element 10 is a double T-shape, but the resonator element 10 of the present embodiment is not limited to such a structure. For example, a tuning fork type, an H type, or the like may be used. In addition, the piezoelectric material of the resonator element 10 may be a material such as ceramics or silicon other than quartz.

  FIG. 8 shows a detailed configuration example of the drive circuit 30 and the detection circuit 60 of the circuit device 20.

  The drive circuit 30 includes an amplifier circuit 32 to which the feedback signal DI from the vibration piece 10 is input, a gain control circuit 40 that performs automatic gain control, and a drive signal output circuit 50 that outputs the drive signal DQ to the vibration piece 10. . A synchronization signal output circuit 52 that outputs the synchronization signal SYC to the detection circuit 60 is also included. The configuration of the drive circuit 30 is not limited to that shown in FIG. 8, and various modifications such as omitting some of these components or adding other components are possible.

  The amplification circuit 32 (I / V conversion circuit) amplifies the feedback signal DI from the vibration piece 10. For example, a current signal DI from the vibrating piece 10 is converted into a voltage signal DV and output. The amplifier circuit 32 can be realized by an operational amplifier, a feedback resistor element, a feedback capacitor, or the like.

  The drive signal output circuit 50 outputs a drive signal DQ based on the signal DV amplified by the amplifier circuit 32. For example, when the drive signal output circuit 50 outputs a rectangular wave (or sine wave) drive signal, the drive signal output circuit 50 can be realized by a comparator or the like.

  A gain control circuit 40 (AGC: Auto Gain Controller) outputs a control voltage DS to the drive signal output circuit 50 to control the amplitude of the drive signal DQ. Specifically, the gain control circuit 40 monitors the signal DV and controls the gain of the oscillation loop. For example, in the drive circuit 30, in order to keep the sensitivity of the gyro sensor constant, it is necessary to keep the amplitude of the drive voltage supplied to the vibration piece 10 (drive vibration piece) constant. Therefore, a gain control circuit 40 for automatically adjusting the gain is provided in the oscillation loop of the drive vibration system. The gain control circuit 40 automatically variably adjusts the gain so that the amplitude of the feedback signal DI from the vibrating piece 10 (vibration speed v of the vibrating piece) is constant. The gain control circuit 40 can be realized by a full-wave rectifier for full-wave rectifying the output signal DV of the amplifier circuit 32, an integrator for integrating the output signal of the full-wave rectifier, or the like.

  The synchronization signal output circuit 52 receives the signal DV amplified by the amplification circuit 32 and outputs a synchronization signal SYC (reference signal) to the detection circuit 60. The synchronization signal output circuit 52 performs a binarization process on the sine wave (alternating current) signal DV to generate a rectangular wave synchronization signal SYC, and a phase adjustment circuit (transition circuit) that adjusts the phase of the synchronization signal SYC. Etc.).

  The detection circuit 60 includes charge voltage conversion circuits 61 and 62 (Q / V conversion circuit), a differential amplifier circuit 63, a synchronous detection circuit 81, an offset adjustment circuit 64, a filter circuit 65, a sensitivity adjustment circuit 66, and an output circuit 67. .

  The charge voltage conversion circuits 61 and 62 receive the first and second detection signals IQ1 and IQ2 from the vibrating piece 10, perform charge voltage conversion, and output voltage signals VQ1 and VQ2. The charge voltage conversion circuits 61 and 62 can be realized by an operational amplifier in which the analog reference voltage VRF is input to the positive input terminal, a feedback capacitor provided between the output terminal and the negative input terminal of the operational amplifier, or the like.

  The differential amplifier circuit 63 amplifies the difference between the signals VQ1 and VQ2 and outputs a voltage signal VSZ. The differential amplifier circuit 63 can be realized by an operational amplifier, a resistance element, or the like, and can be realized by the same configuration as the amplifier circuit 400 of FIG. For example, the analog reference voltage VRF is input to the other end of a resistance element whose one end is connected to the positive input terminal of the operational amplifier.

  The synchronous detection circuit 81 performs synchronous detection of the signal VSZ based on the synchronous signal SYC from the drive circuit 30, and outputs a voltage signal VDK. The synchronous detection circuit 81 can be realized by a switch circuit composed of an inverting amplifier circuit (such as an operational amplifier or a resistance element) or a filter (such as a resistance element or a capacitor) that smoothes the output signal of the switch circuit. The analog reference voltage VRF is input to, for example, the positive input terminal of the operational amplifier of the inverting amplifier circuit.

  The offset adjustment circuit 64 adjusts the DC offset of the signal VDK and outputs a voltage signal VDF. The offset adjustment circuit 64 can be realized by an operational amplifier, a variable resistance circuit, or the like. One end of the variable resistance circuit is connected to the output terminal of the operational amplifier, and the analog reference voltage VRF is input to the other end. The variable resistance circuit can variably adjust the voltage dividing ratio, and the divided voltage is input to the negative input terminal of the operational amplifier.

  The filter circuit 65 low-pass filters the signal VDF and outputs a voltage signal VFL. The filter circuit 65 can be realized by an SCF (Switched Capacitor Filter) or the like. The analog reference voltage VRF is input as an analog reference voltage of the SCF.

  The sensitivity adjustment circuit 66 is a circuit for adjusting the detection sensitivity of the angular velocity, amplifies the amplitude of the signal VFL with a gain proportional to the power supply voltage VDD, and outputs a voltage signal VKC. The sensitivity adjustment circuit 66 can be realized by an operational amplifier, a resistance element, a variable resistance circuit, or the like. The analog reference voltage VRF is input as the analog reference voltage of the sensitivity adjustment circuit 66.

  The output circuit 67 buffers the signal VKC and outputs a signal VOUT. The signal VOUT is a signal including angular velocity information, and the difference between the signal VOUT and the analog reference voltage VRF is proportional to the angular velocity. The output circuit 67 can be realized by a low-pass filter (such as a resistance element or a capacitor) or a voltage follower (operational amplifier). The analog reference voltage VRF is input as an analog reference voltage for the low-pass filter.

  As described above, the circuit device 20 of the present embodiment includes the analog reference voltage generation circuit 300 and the amplifier circuit to which the analog reference voltage VRF from the analog reference voltage generation circuit 300 is input to the analog reference voltage input node. The analog reference voltage input node is a node to which the analog reference voltage VRF is input in each circuit included in the detection circuit 60 described above.

  As described above, the analog reference voltage VRF in which the noise is reduced by the analog reference voltage generation circuit 300 is input to the amplifier circuit of the circuit device 20, so that the S / N reduction due to the noise of the analog reference voltage VRF can be suppressed. .

  The circuit device 20 according to the present embodiment includes a detection circuit 60. The detection circuit 60 includes an amplifier circuit to which the analog reference voltage VRF from the analog reference voltage generation circuit 300 is input to the analog reference voltage input node, and detects according to the physical quantity output from the physical quantity transducer (vibration piece 10). Based on the signals IQ1 and IQ2, physical quantity information (signal VOUT) corresponding to the physical quantity is output.

  The amplification circuit included in the detection circuit 60 is included in at least one of the charge-voltage conversion circuits 61 and 62, the differential amplification circuit 63, the sensitivity adjustment circuit 66, the offset adjustment circuit 64, the synchronous detection circuit 81, and the filter circuit 65. It is an amplifier circuit.

  Thus, even if noise is superimposed on the power supply line of the physical quantity sensor by supplying the analog reference voltage VRF from the analog reference voltage generation circuit 300 to the detection circuit 60 that detects the physical quantity in the physical quantity sensor, the influence thereof Physical quantity can be detected without receiving. For example, the detection accuracy of physical quantities (for example, the S / N of the angular velocity signal in the gyro sensor 510) can be improved even in in-vehicle applications that require resistance to disturbance noise. The detection circuit 60 includes a multi-stage amplifier circuit, and noise propagated from the analog reference voltage VRF to the output of each stage is amplified by the subsequent amplifier circuit. In this respect, since noise of the analog reference voltage VRF is reduced in this embodiment, the effect of noise reduction is great in such a multistage amplifier circuit.

6). FIG. 9 shows an example of a mobile object and an electronic device including the circuit device 20 of the present embodiment. The circuit device 20 of the present embodiment can be incorporated into various moving bodies such as cars, airplanes, motorcycles, bicycles, and ships. The moving body is a device / device that includes a driving mechanism such as an engine or a motor, a steering mechanism such as a steering wheel or a rudder, and various electronic devices, and moves on the ground, the sky, or the sea.

  The automobile 206 is schematically shown as a specific example of a moving object. The automobile 206 incorporates a gyro sensor 510 (sensor) having the resonator element 10 and the circuit device 20. The gyro sensor 510 can detect the posture of the vehicle body 207. A detection signal of the gyro sensor 510 is supplied to the vehicle body posture control device 208. The vehicle body posture control device 208 can control the hardness of the suspension and the brakes of the individual wheels 209 according to the posture of the vehicle body 207, for example. In addition, such posture control can be used in various mobile objects such as a biped robot, an aircraft, and a helicopter. The gyro sensor 510 can be incorporated in realizing the attitude control.

  The digital still camera 610 and the biological information detection device 620 are schematically shown as specific examples of electronic devices. As described above, the circuit device 20 of the present embodiment can be applied to various electronic devices such as the digital still camera 610 and the biological information detection device 620 (wearable health device, such as a pulse meter, a pedometer, and an activity meter). For example, in the digital still camera 610, camera shake correction using a gyro sensor or an acceleration sensor can be performed. Further, in the biological information detection device 620, it is possible to detect a user's body movement or an exercise state using a gyro sensor or an acceleration sensor.

  The robot 630 is schematically shown as a specific example of a mobile object or an electronic device. As described above, the circuit device 20 of the present embodiment can also be applied to the movable part (arm, joint) and main body part of the robot 630. The robot 630 can be assumed to be either a moving body (running / walking robot) or an electronic device (non-running / non-walking robot). In the case of a traveling / walking robot, for example, the circuit device 20 of the present embodiment can be used for autonomous traveling.

  Although the present embodiment has been described in detail as described above, it will be easily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention. For example, a term described at least once together with a different term having a broader meaning or the same meaning in the specification or the drawings can be replaced with the different term in any part of the specification or the drawings. All combinations of the present embodiment and the modified examples are also included in the scope of the present invention. Further, the configuration and operation of the analog reference voltage generation circuit, the resonator element, the circuit device, the physical quantity sensor, the electronic device, the moving body, and the like are not limited to those described in the present embodiment, and various modifications can be made.

DESCRIPTION OF SYMBOLS 1 ... Base part, 2, 3 ... Connection arm, 4-7 ... Drive arm, 8, 9 ... Detection arm, 10 ... Vibrating piece,
DESCRIPTION OF SYMBOLS 20 ... Circuit apparatus, 30 ... Drive circuit, 32 ... Amplifier circuit, 40 ... Gain control circuit,
50 ... Drive signal output circuit, 52 ... Synchronization signal output circuit, 60 ... Detection circuit,
61, 62 ... charge voltage conversion circuit, 63 ... differential amplification circuit, 64 ... offset adjustment circuit,
65 ... Filter circuit, 66 ... Sensitivity adjustment circuit, 67 ... Output circuit, 81 ... Synchronous detection circuit,
DESCRIPTION OF SYMBOLS 110 ... Processing apparatus, 112 ... A / D conversion circuit, 140 ... Control part, 206 ... Car,
207 ... body, 208 ... body posture control device, 209 ... wheel,
300 ... Analog reference voltage generation circuit, 310 ... Voltage division circuit,
320 ... first buffer circuit, 330 ... second buffer circuit,
340 ... AC component extraction circuit, 342 ... High-pass filter, 350 ... Subtraction circuit,
360 ... low pass filter, 400 ... amplification circuit, 500 ... electronic equipment,
510 ... Gyro sensor, 520 ... Processing unit, 530 ... Memory, 540 ... Operation unit,
550 ... Display unit, 610 ... Digital still camera, 620 ... Biological information detection device,
630 ... Robot,
IQ1, IQ2 ... detection signal, OP1 ... first operational amplifier, OP2 ... second operational amplifier,
RA1: first resistance element, RA2: second resistance element, RD1: third resistance element,
RD2 ... fourth resistance element, RD3 ... fifth resistance element, RD4 ... sixth resistance element,
VB: Divided voltage, VDD: Power supply voltage, VRF: Analog reference voltage

Claims (12)

A voltage dividing circuit for dividing the power supply voltage and outputting the divided voltage;
An AC component extraction circuit that extracts an AC component from a first signal that is a signal based on the divided voltage;
A subtraction circuit that performs a subtraction process between the second signal that is a signal based on the divided voltage and the output signal of the AC component extraction circuit to output an analog reference voltage;
An analog reference voltage generation circuit comprising: In claim 1,
A first buffer circuit that receives the divided voltage and outputs the first signal having a voltage corresponding to the divided voltage;
A second buffer circuit that receives the divided voltage and outputs the second signal having a voltage corresponding to the divided voltage;
An analog reference voltage generation circuit comprising: In claim 1 or 2,
The AC component extraction circuit includes:
An analog reference voltage generation circuit comprising a high-pass filter that receives the first signal and extracts an AC component of the first signal. In claim 3,
The AC component extraction circuit includes:
A first operational amplifier in which an output signal of the high-pass filter is input to a first input node;
A first resistance element provided between a second input node of the first operational amplifier and an output node of the first operational amplifier;
A second resistance element provided between the second input node of the first operational amplifier and a node of a low-potential-side power supply voltage;
An analog reference voltage generation circuit comprising: In any one of Claims 1 thru | or 4,
The subtraction circuit
A second operational amplifier;
A third resistance element provided between a node to which the second signal is input and a first input node of the second operational amplifier;
A fourth resistance element provided between the first input node of the second operational amplifier and a node of a low-potential-side power supply voltage;
A fifth resistance element provided between an output node of the AC component extraction circuit and a second input node of the second operational amplifier;
A sixth resistance element provided between a second input node of the second operational amplifier and an output node of the second operational amplifier;
An analog reference voltage generation circuit comprising: In any one of Claims 1 thru | or 5,
An analog reference voltage generation circuit, comprising: a low-pass filter that outputs the analog reference voltage from the subtraction circuit by low-pass filtering. An analog reference voltage generation circuit according to any one of claims 1 to 6,
An amplifier circuit in which the analog reference voltage from the analog reference voltage generation circuit is input to an analog reference voltage input node;
A circuit device comprising: An analog reference voltage generation circuit according to any one of claims 1 to 6,
The analog reference voltage from the analog reference voltage generation circuit has an amplifier circuit that is input to an analog reference voltage input node, and corresponds to the physical quantity based on a detection signal corresponding to the physical quantity output from the physical quantity transducer. A detection circuit that outputs physical quantity information;
A circuit device comprising: In claim 8,
The amplifier circuit is
A circuit device comprising: an amplifier circuit included in at least one of a charge-voltage conversion circuit, a differential amplifier circuit, a sensitivity adjustment circuit, an offset adjustment circuit, a synchronous detection circuit, and a filter circuit of the detection circuit. A circuit device according to claim 8 or 9,
The physical quantity transducer;
A physical quantity sensor characterized by comprising:   An electronic apparatus comprising the circuit device according to claim 7.   A moving body comprising the circuit device according to claim 7.

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