JP2002246854A - Voltage detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage detecting device using a semiconductor type pressure sensor, which minimizes the fluctuation of the offset voltage of a whole circuit and has excellent temperature characteristics. SOLUTION: A differential amplifier circuit 9 for is constituted of first, second, and third arithmetic amplifiers 9a, 9b, and 9c mounted on a circuit board 5, and the first and second arithmetic amplifiers 9a and 9b input first and second output voltages outputted by a semiconductor type pressure sensor 4, and the third arithmetic amplifier 9c inputs first and second amplified voltages outputted by the first and second arithmetic amplifiers 9a and 9b, and amplifies a difference between the first and second amplified voltages. A first integrated circuit 11 is constituted of the first and second arithmetic amplifiers 9a and 9b which are integrated into one package.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor having a semiconductor sensor (hereinafter referred to as a pressure sensor), and more particularly to a differential amplifier circuit comprising a plurality of operational amplifiers for amplifying an output voltage of the pressure sensor. And a pressure detecting device.

[0002]

2. Description of the Related Art As a pressure detecting device, a pressure sensor comprising a pressure sensing element having a piezoresistive effect on a silicon substrate in a bridge shape is used to detect the pressure of a fluid such as gas or liquid. It has been known.

[0003] Such a pressure detecting device includes a circuit board electrically connected to the pressure sensor by a wire by wire bonding, and a first circuit for inputting an output voltage output from the pressure sensor onto the circuit board. , A second operational amplifier, and a third operational amplifier, which receives first and second amplified voltages output from the first and second operational amplifiers and amplifies a difference between the first and second amplified voltages. And a differential amplifier circuit comprising an operational amplifier.

[0004] The differential amplifier circuit in the pressure detecting device is composed of a plurality of operational amplifiers. Recently, as semiconductor integrated technology has advanced, these operational amplifiers have been integrated into one package using the same IC chip. It is generalized to configure the differential amplifier circuit by using the integrated circuit described above. The integrated circuit has various element configurations such as two-element (two operational amplifiers) or four-element (four operational amplifiers), but in a small electronic device such as the pressure detection device, The drive circuit is laid out using an integrated circuit that can be reduced in size.

[0005]

In the pressure detecting device having the above-described configuration, when the differential amplifier circuit is configured using the integrated circuit, at least three or more operational amplifiers are required. For example, when three operational amplifiers are required, the differential amplifier circuit may be configured using an integrated circuit having three or four elements. However, since these integrated circuits are large, the pressure detection device It is not suitable as a mounting component to be mounted on a circuit board in a small electronic device such as the one described above. Are prepared and mounted on the circuit board.

However, when the differential amplifier circuit is configured using a plurality of the integrated circuits, the integrated circuits are formed of a semiconductor material. The offset voltage of the operational amplifier varies among the integrated circuits of different IC chips, and depending on the circuit layout of the operational amplifier of each of the integrated circuits, it is desirable to eliminate the variation of the offset voltage. In the detection device, since the variation in the offset voltage of the entire circuit is increased and the temperature characteristic is increased, the pressure detection device used under severe conditions such as a vehicle cannot detect an accurate pressure. There was such a problem.

Therefore, the present invention focuses on the above problems, and provides a pressure detecting device using a semiconductor type pressure sensor, which minimizes variations in offset voltage of the entire circuit and has excellent temperature characteristics. Things.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides first and second output signals from a semiconductor pressure sensor.
First and second operational amplifiers for inputting a second output voltage;
First and second output from the first and second operational amplifiers
And a third operational amplifier for inputting the amplified voltage and amplifying the difference between the first and second amplified voltages, and forming the first and second operational amplifiers in one package. Of the integrated circuit.

Also, first and second operational amplifiers for inputting first and second output voltages output from the semiconductor pressure sensor, and first and second operational amplifiers output from the first and second operational amplifiers, respectively. A third operational amplifier configured to receive a second amplified voltage and amplify a difference between the first and second amplified voltages to form a differential amplifier circuit, and to integrate the first and second operational amplifiers into one package And the third operational amplifier is constituted by a one-packaged second integrated circuit different from the first integrated circuit.

The semiconductor integrated pressure sensor further includes a fourth operational amplifier for forming a constant current source circuit for supplying a constant current to the semiconductor pressure sensor, and the third integrated amplifier and the third operational amplifier are provided by the second integrated circuit. And 4 operational amplifiers.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, a pressure detecting device A includes a lower case 1, an upper case 2, a base plate 3, a semiconductor type pressure sensor (hereinafter, referred to as a pressure sensor) 4, a circuit board 5,
It is mainly composed of a shield plate 6 and a terminal unit 7.

The lower case 1 is formed by outsert molding a flange portion 1b made of a resin material such as PBT on a pressure introducing portion 1a which is a hexagonal member having a mounting screw portion made of a metal material such as SUM. A pressure introducing hole 1c is formed substantially at the center of the pressure introducing section 1a.

The upper case 2 is formed of a resin material such as PBT, and is disposed and fixed by thermally caulking the open end of the upper case 2 to the flange 1b of the lower case 1. The pressure sensor 4, the circuit board 5, and the like are stored. The upper case 2 includes a connector 2a for supplying power and outputting signals via electrode leads described later.

The base plate 3 is made of a metal material such as Kovar, and has a flange portion 3a to be fixed to the upper end of the pressure introducing portion 1a of the lower case 1 by resistance welding.
A mounting portion 3b for disposing the pressure sensor 4 is provided at a position one step higher than the flange portion 3a. A hole 3c for transmitting pressure to the pressure sensor 4 is provided substantially at the center of the mounting portion 3b.

As shown in FIGS. 1 and 2, the pressure sensor 4 includes a semiconductor chip 4a having a diaphragm formed by thinning a semiconductor substrate such as silicon, and a glass pedestal 4b.
The semiconductor chip 4a and the glass pedestal 4b are joined by an anodic bonding method, and the pressure of the fluid introduced from the pressure introduction path 4c provided in the glass pedestal 4b is increased by the diaphragm. Then, the displacement of the diaphragm is detected.

As shown in FIG. 3, the pressure sensor 4 diffuses impurities such as boron into a portion corresponding to the diaphragm, thereby forming four pressure-sensitive elements R1 to R4 having a piezoresistance effect. The resistance R
A bridge circuit is formed by wiring patterns 1 to R4 using a conductive material such as aluminum, and the pressure is detected by a change in the output voltage of the bridge circuit due to the displacement of the diaphragm.

The circuit board 5 has a predetermined wiring pattern (not shown) formed by using paper phenol, resin containing glass fiber, ceramic or the like as a support material. The circuit board 5 has a flange portion of the lower case 1. It is arranged on a mounting portion 1d provided above 1b.

As shown in FIGS. 2 and 3, first, second, and third operational amplifiers 9a, 9b, and 9c for constituting a differential amplifier circuit 9 in the pressure sensor 4 are provided on the circuit board 5.
First and second integrated circuits 11 and 12 each including a fourth operational amplifier 10a for configuring the constant current source circuit 10 in the pressure sensor 4 are mounted at predetermined locations. Also, on one end side of the circuit board 5, trimming resistors Ra to Rf such as a trimmable chip resistor and a pressure film printing resistor for adjusting the output voltage from the pressure sensor 4 and adjusting the magnification in the differential amplifier circuit 9 are provided. Are arranged in a row.

The differential amplifying circuit 9 includes first and second operational amplifiers 9a and 9b for inputting first and second output voltages output from the pressure sensor 4, respectively, and first and second operational amplifiers 9a and 9b. A third operational amplifier 9c which receives the first and second amplified voltages output from the operational amplifiers 9a and 9b and amplifies the difference between the first and second amplified voltages.

The circuit board 5 has an arrangement in which the peripheral edge of the circuit board 5 is supported by the mounting portion 1d of the lower case 1, and the circuit board 5 is provided on the base plate 3 at substantially the center of the circuit board 5. When the circuit board 5 is disposed on the mounting portion 1d of the lower case 1 from above the pressure sensor 4 to be provided, a storage hole 5a for disposing the circuit board 5 so as to surround the pressure sensor 4 is provided. Is formed.

In the vicinity of the storage hole 5a of the circuit board 5, an electric current is applied through a wire 13 made of a conductive material such as gold while corresponding to the electrode pad formed on the pressure sensor 4. An electrode portion 5b is provided for electrical connection.

Each of the first and second integrated circuits 11 and 12 mounted on the circuit board 5 is obtained by integrating two operational amplifiers into one package with the same IC chip, as shown in FIG. As described above, the first and second operational amplifiers 9a and 9b in the differential amplifier circuit 9 are constituted by the first integrated circuit 11, and the third operational amplifier 9 in the differential amplifier circuit 9
The second integrated circuit 12 constitutes c and a fourth operational amplifier 10a that functions as a buffer for supplying a reference voltage in the constant current source circuit 10.

The circuit board 5 is provided with a lead terminal 15 electrically connected to an electrode lead 13 disposed on the connector portion 2a of the upper case 2 via the terminal unit 8 and a through capacitor 14 having lead pins. ing. The feedthrough capacitor 14 absorbs external noise superimposed on the power supply line and the signal line.

The shield plate 6 is made of a metal material such as SPTE, and is disposed between the terminal unit 7 disposed in the concave portion 2b of the upper case 2 and the flange portion 1b of the lower case 2 in a sandwiched state. .

The shield plate 6 has a holder 6a having a hole for disposing a feedthrough capacitor 14 cut and raised substantially perpendicularly to the mounting surface on which the terminal unit 7 is disposed. The feedthrough capacitor 14 is disposed and fixed in the hole provided through solder.

The terminal unit 7 is formed by inserting an electrode lead 13 into a resin material such as PBT. The terminal unit 7 is fitted into a concave portion 2b provided in the connector portion 2a of the upper case 2, and the electrode lead 13 is inserted into a hole 2c provided substantially at the center of the bottom surface of the concave portion 2b. It is arranged on the writing surface.

The above components constitute a pressure detecting device A.

The pressure detecting device A includes first and second output signals which are output when the semiconductor chip 4a of the pressure sensor 4 is deformed.
And the first and second operational amplifiers 9a and 9b for inputting the first and second operational amplifiers 9a and 9b, respectively. ,
A differential amplifier circuit 9 comprising a third operational amplifier 9c for amplifying the difference between the second amplified voltages is formed on the circuit board 5,
The first and second operational amplifiers 9a and 9b, which are the pre-stage circuits in the differential amplifier circuit 9, are constituted by the first integrated circuit 11 which is packaged with the same IC chip in one package. A third operational amplifier 9c and a fourth operational amplifier 10a acting as a buffer for supplying a reference voltage to the pressure sensor 4 are packaged in the same IC chip different from the first integrated circuit 11 in a second package. Of the integrated circuit 12.

Therefore, the first and second operational amplifiers 9a, 9 which are circuits preceding the differential amplifier circuit 9 in the pressure sensor 4, which greatly affect the variation of the offset voltage of the entire circuit.
Since b is constituted by the first integrated circuit 11 packaged in one package, the difference between the offset voltage and the temperature characteristic between the operational amplifiers 9a and 9b can be relatively reduced, whereby the variation of the offset voltage can be reduced. It will be effectively removed. Therefore, it is possible to suppress the variation of the offset voltage as a whole circuit after the third operational amplifier 9c, which is a subsequent circuit of the differential amplifier circuit 9, and to keep the temperature characteristics of the offset voltage small. A pressure detecting device A capable of detecting an accurate pressure even in an environment where the change is rapid (for example, a pressure detecting device for a vehicle) can be obtained.

When the constant current source circuit 10 is provided as in the embodiment of the present invention, the fourth operational amplifier 10a acting as a buffer is required.
By configuring the fourth operational amplifier 10a with the integrated circuit 12, the circuit can be designed without increasing the size of the circuit board 5.

In the embodiment of the present invention, the constant current source circuit 10 is provided as a circuit configuration of the pressure detecting device A. However, in the present invention described in claim 1 of the present invention, The circuit configuration does not necessarily need to include the constant current source circuit 10, and the first and second operational amplifiers 9a and 9b, which are the circuits preceding the differential amplifier circuit 9 that is most affected by the offset voltage variation, are connected to the same IC. Any circuit configuration may be used as long as it is configured by an integrated circuit integrated into one package with a chip.

[0033]

According to the present invention, there are provided first and second operational amplifiers for inputting first and second output voltages output from a semiconductor pressure sensor, and output signals from the first and second operational amplifiers. And a third operational amplifier configured to receive the first and second amplified voltages and amplify the difference between the first and second amplified voltages. , The first and second operational amplifiers are configured by an integrated circuit in a single package, and in a pressure detection device using the semiconductor type pressure sensor, variations in offset voltage of the entire circuit are minimized, A pressure detector excellent in temperature characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a pressure detecting device according to an embodiment of the present invention.

FIG. 2 is a plan view showing a state in which a circuit board disposed in a lower case of the pressure detection device is viewed from above.

FIG. 3 is a circuit diagram of the pressure detection device.

[Explanation of symbols]

 A pressure detecting device 4 semiconductor pressure sensor 5 circuit board 9 differential amplifier circuit 9a first operational amplifier 9b second operational amplifier 9c third operational amplifier 10 constant current source circuit 10a fourth operational amplifier 11 first integration Circuit 12 Second Integrated Circuit

Claims (3)

[Claims] 1. A first and second operational amplifier for receiving first and second output voltages output from a semiconductor pressure sensor, and first and second operational amplifiers output from the first and second operational amplifiers.
And a third operational amplifier configured to receive the second amplified voltage and amplify the difference between the first and second amplified voltages to form a differential amplifier circuit. A pressure detecting device comprising a packaged integrated circuit. 2. The first and second operational amplifiers for inputting first and second output voltages output from a semiconductor pressure sensor, and the first and second operational amplifiers output from the first and second operational amplifiers.
A third operational amplifier configured to receive a second amplified voltage and amplify a difference between the first and second amplified voltages to form a differential amplifier circuit, and to integrate the first and second operational amplifiers into one package A pressure detecting device, comprising: a first integrated circuit; and a third operational amplifier, wherein the third operational amplifier is constituted by a second integrated circuit which is different from the first integrated circuit and is formed into a single package. 3. A fourth operational amplifier for forming a constant current source circuit for supplying a constant current to the semiconductor type pressure sensor, wherein the third integrated amplifier and the third operational amplifier are provided by the second integrated circuit. 3. The pressure detecting device according to claim 2, wherein the pressure detecting device comprises four operational amplifiers.