JPH102820A - Semiconductor pressure converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regulate the sensitivity and zero point of a pressure converter by providing a plurality of resistance networks within a processing circuit for strain gauge bridge output, selectively connecting a regulating resistance of every column by an external signal, and varying the output current of the resistance networks. SOLUTION: This device has resistance networks RM1-RMd of the same structure in which input terminals I1-I3 are connected to a bridge piece side output Vg, a power source Vcc, and a ground Gnd, respectively, output terminals O1-O3 are connected to the reversion input terminal of an arithmetic amplifier OP1, and current bypassing terminals A1-A3 are connected to the output of a buffer arithmetic amplifier OP3. The network RM1 has a start end resistance Rag, unit serial resistances Ra1-Ra4 having a resistance value ρ1 , a terminal serial resistance Ra5 having a resistance value 2ρ1 , regulating resistances of every column ra1-ra5, and switches Sa1-Sa5 for selectively connecting resistances ra1-ra5 to the terminal O1 or A1 by an external signal. The sensitivity can be regulated with a resolution of 25 in the network RM1, and the zero point potential is regulated in the networks RM2, RM3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure transducer suitable for applications requiring small, lightweight and high-precision characteristics, such as for automobiles, and more particularly to the adjustment of the sensitivity of output signals and the zero-point potential. The present invention relates to a semiconductor pressure transducer having a built-in circuit for easily compensating its temperature characteristics and the like by using an external digital signal.

[0002] In the drawings, the same reference numerals indicate the same or corresponding parts.

[0003]

2. Description of the Related Art In general, a semiconductor pressure transducer has a built-in circuit for amplifying the output of a strain gauge, and is used in a state where a pressure sensitivity is adjusted and a zero point potential is adjusted. In particular, when used in an environment with a large temperature change, such as for an automobile, it is necessary to compensate for the temperature characteristics of the sensitivity and the zero point potential.

[0004] In a small and light pressure transducer composed of a monolithic IC or a hybrid IC, a widely used method for adjusting or compensating them is trimming of a resistor by laser or sandblast. This trimming is, as shown in FIG. 4, a thick-film or thin-film resistor 2 having a size that can be trimmed between, for example, conductor electrodes 1 in a signal processing circuit in a semiconductor pressure transducer.
Is provided, and a part of the resistor 2 is vaporized or insulated by the heat of the laser beam 4 or mechanically cut by sand blast to change the resistance value in an analog manner to obtain the target characteristic. Is to do so. Note that reference numeral 3 in FIG. 4 denotes a part of the resistor 2 removed or converted into an insulator by the trimming.

[0005]

In the conventional trimming method described above, since the resistance value is changed in an analog manner, the resolution of the adjustment can be easily increased, particularly by using a method such as L-cut or W-cut. However, this trimming method has the following problems. (1) In order to process a fine pattern, it is necessary to align a chip or a circuit board of a semiconductor pressure transducer in advance, and it takes more time to improve the accuracy. (2) The resistor portion at the boundary with the trimmed portion is unstable in material, so that the resistance is liable to change with time. (3) At the time of trimming, the chip or the circuit board is exposed, so that the chip or the circuit board is easily damaged or damaged.

Accordingly, the present invention solves such a problem,
It does not require pre-positioning, can be trimmed in a short time regardless of accuracy, has little change in resistance over time, can be trimmed after mounting is completed, and is a relatively simple circuit. An object of the present invention is to provide a semiconductor pressure transducer having the above structure.

[0007]

According to a first aspect of the present invention, there is provided a semiconductor pressure transducer which is formed on a silicon diaphragm by diffusion, and has a predetermined power supply voltage (Vcc) and a ground potential (Gnd). Are given to predetermined terminals, respectively, and a plurality of strain gauges (RG1 to RG
4) and a current corresponding to the output voltage (Vg) of the strain gauge generated according to the pressure applied to the diaphragm is passed through a feedback resistor (Rf) connecting the inverting input terminal and the output terminal to be converted into a voltage. Output voltage of semiconductor pressure transducer (Vo
ut), and a signal processing circuit for amplifying and adjusting the output voltage of the strain gauge,
A semiconductor pressure transducer provided on the same or a plurality of silicon chips that may include a resistance substrate, wherein the signal processing circuit has first, second, and third three network terminals, respectively, A predetermined or one or more fixed or variable potentials existing or generated in the semiconductor pressure transducer and different from the input potentials of the second or third network terminals are provided to the network terminal (such as the input terminal I1). Is input,
A second network terminal (such as an output terminal O1) is connected to the inverting input terminal of the operational amplifier, and a third network terminal (such as a current bypass terminal A1) is connected via a buffer circuit composed of an operational amplifier OP3. A) a resistor network connected to a portion independent of the operational amplifier at substantially the same potential as the second network terminal, the first network terminal (input terminal I
1) and the third network terminal
A plurality of unit series resistor having the same resistance value in order from the network terminal side (such as [rho ₁₎ (such as Ra1～Ra4) and, terminating the series resistor having a fold resistance of the unit series resistance (such 2.rho ₁₎ ( Ra5, etc.) are connected in series one by one, and one end of each of a plurality of unit series resistors and a terminating series resistor forming the resistor series circuit on the first network terminal side. The digitized adjusting resistors (ra1 to ra5) each having a resistance value (such as 2ρ1) twice the unit series resistance as ₁
Or one or more resistor circuits, one end of each of which is connected, and the other end of each digit-wise adjustment resistor is selectively connected to either the second or third network terminal. Net (RM
1 to RM5) and a selective connection for selectively connecting each digit-adjustment resistor of each of the resistor networks according to an external digital signal so that the connection is stored even when the power is cut off. Means, and at the inverting input terminal of the operational amplifier, a current input from a digit-by-digit adjustment resistor selectively connected to a second network terminal of each of the resistor networks is added, and a voltage is added to the voltage by the feedback resistor. It is converted so as to be superimposed on the output voltage of the semiconductor pressure transducer.

According to a second aspect of the present invention, there is provided the semiconductor pressure transducer according to the first aspect, wherein a potential input to the first network terminal is output from a strain gauge generated according to the pressure. The potential or the potential corresponding to the output potential obtained through signal processing of the output potential (via a buffer circuit including an operational amplifier OP2), the power supply voltage, or the ground potential. The sensitivity or / and zero potential of the strain gauge to the pressure signal can be adjusted according to the external digital signal.

According to a third aspect of the present invention, in the semiconductor pressure transducer according to the first or second aspect, the feedback resistor has a large positive temperature dependency (Rft).
To compensate for the sensitivity-temperature characteristic of the output voltage of the semiconductor pressure transducer. According to a fourth aspect of the present invention, in the semiconductor pressure transducer according to any one of the first to third aspects, at least one or a plurality of resistance networks (RM4, RM5) among the resistance networks are provided.
Etc.) between the first network terminal and the resistor series circuit in series with each other.
t, etc.), so that the sensitivity temperature characteristic of the output voltage or / and the temperature characteristic of the zero potential of the semiconductor pressure transducer can be compensated.

According to a fifth aspect of the present invention, there is provided a semiconductor pressure transducer according to any one of the first to fourth aspects, wherein at least one of the resistance networks or a plurality of the resistance networks is provided. The first end resistances (Ra0 to Ra0) having a large temperature dependency between the first network terminal and the second network terminal, respectively.
A resistance corresponding to Rc0 or the like is inserted so that the sensitivity temperature characteristic of the output voltage or the temperature characteristic of the zero-point potential of the semiconductor pressure transducer can be compensated.

The operation of the present invention is as follows. That is, the strain gauge bridges RG1 to RG on the silicon diaphragm
4, the reference potential side terminal G1 and the non-inverting input terminal among the signal output terminals are set to the same potential, a current proportional to the signal output voltage Vg of the strain gauge bridge flows through the feedback resistor Rf, and Vg is amplified at the output terminal. In a semiconductor pressure converter having an operational amplifier OP1 for generating a converter output voltage Vout,
The signal processing circuit is selectively connected by a digital signal from the outside via a switch, and receives at least a unit series resistance from a network input terminal to which a potential of each part described below in the pressure transducer is input to a network output terminal. And 2 ^N (where N is the number of the stage (digit) where the digit-specific adjustment resistor is present in the resistor network) through a resistor series circuit composed of a resistor and a series resistor. One or a plurality of resistor networks each having a digit-by-digit adjustment resistor are provided, the network output terminal of which is connected to the inverting input terminal of the operational amplifier OP1, and the current of the network output terminal is superimposed on the current of the feedback resistor Rf. Adjust the output voltage Vout of the pressure transducer.

In this way, in the resistance network, the sensitivity of the pressure transducer output voltage Vout is adjusted by the resistance network RM1 in which the potential of the network input terminal is set to the potential of the output signal of the strain gauge bridge. The zero point potential of the pressure transducer output voltage Vout is adjusted by a resistor network RM2 in which the potential of the network input terminal is the power supply voltage Vcc or a resistor network RM3 in which the potential of the network input terminal is the ground potential Gnd. In the embodiment, the total number of stages (digits) in which the digit-by-digit adjustment resistors exist (in other words, the total number of digit-by-digit adjustment resistors or switches in the resistor network concerned) is five, and the resolution at a resolution of 2 ^-5 is obtained. Adjustment is possible.

The feedback resistor of the operational amplifier OP1 may be a feedback resistor Rft having a large positive temperature dependency, or a start-point series resistor Rdt having a large temperature dependency may be connected in series between the network input terminal and the resistor series circuit. , Ret, etc., are used to compensate for the sensitivity of the pressure transducer output voltage Vout and the temperature characteristic of the zero point potential.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 shows a circuit configuration as a first embodiment of the present invention. In the figure, reference numerals RG1 to RG4 denote semiconductor strain gauges which are dispersed and arranged on a silicon diaphragm by a diffusion process, and are configured in the form of a Wheatstone bridge. Here, Vcc is the drive voltage, Gnd
Is the ground potential. When the silicon diaphragm is deformed by pressure, the connection point G on the voltage detection side of the strain gauge bridge
A differential output voltage Vg is generated between 1 and G2.

RM1, RM2 and RM3 are resistance networks. The input terminal I1 distortion on one side of the potential of the gauge bridge output Vg of the resistor network RM1 ^- and impedance conversion via a buffer circuit composed of the operational amplifier OP2 potential is input, the power supply to the input terminal I2 of the resistor network RM2 Voltage Vcc is input, and ground potential Gnd is input to input terminal I3 of resistance network RM3.

On the other hand, the output terminals O1 to O3 of each of the resistor networks RM1 to RM3 are all connected to the inverting input terminal of the operational amplifier OP1, and a feedback resistor is provided between the inverting input terminal of the operational amplifier OP1 and the output terminal Vout. Rf is connected.
The potential Vg ⁺ on the other side of the output of the strain gauge bridge is input to the non-inverting input terminal of the operational amplifier OP1 via the resistor Ri1, and the non-inverting input terminal of the operational amplifier OP3 forming a buffer circuit via the resistor Ri2. Is also entered.

A1, A2 and A3 are respectively a resistance network RM.
1, RM2 and RM3 are current bypass terminals, all of which are connected to the output terminal of the operational amplifier OP3 constituting this buffer circuit. In the above configuration, the resistance network RM
1 to RM3 and the operation of the entire circuit of FIG. 1 will be described.

FIG. 2 is a circuit diagram showing the resistance network RM1 and its peripheral portion. As shown in FIG.
Is a unit series resistor connected in series in the example from the input terminal I1 side to the start terminal resistor Ra0 directly connecting the input terminal I1 and the output terminal O1, and the input terminal I1 between the input terminal I1 and the current bypass terminal A1. .., Ra4 and a terminating series resistor Ra5, and an input terminal I1 of each of the series resistors Ra1, Ra2,.
Digit-adjustment resistors ra1, one ends of which are connected to the
.., ra5, and the digit-by-digit adjustment resistors ra1,
.., and Sa5. The switches Sa1, Sa2,..., Sa5 are set in advance so that the other ends of the ra2,... ra5 are respectively switched to the output terminal O1 side or the current bypass terminal A1.

As described above, in the circuit of FIG. 2, the positive potential Vg ⁺ of the strain gauge bridge output is supplied to the non-inverting input terminal of the operational amplifier OP1 via the resistor Ri1 and to the resistor Ri2.
Through the non-inverting input terminal of the operational amplifier OP3. Here, the resistors Ri1 and Ri2 are connected to the operational amplifier OP
If the input impedance of OP1 and OP3 is sufficiently small and the offset voltage and offset current of OP1 and OP3 are negligible, the resistance network RM
The potentials of the output terminal O1 and the current bypass terminal A1 are both Vg ⁺ .

Therefore, the switches Sa1 to Sa5 are connected to the terminal O1.
The switch Sa1 of each digit-adjustment resistor ra1 to ra5 in the case of conduction to the terminal A1 and the case of conduction to the terminal A1.
The potential on the Sa5 side does not change, and this digit-by-digit adjustment resistor ra1
The current flowing through ra5 does not change. Following formula where _one resistance ρ of the unit series resistance Ra1～Ra4, also the resistance of the terminating series resistor Ra5 and each digit by adjusting the resistance ra1~ra5 the final stage is set to be in 2.rho _1, in this circuit (1) holds.

[0021]

I1 = i5 ′ = i4 ′ / 2 i4 = i4 ′ = i3 ′ / 2 i3 = i3 ′ = i2 ′ / 2 i2 = i2 ′ = i1 ′ / 2 i1 = i1 ′ (1) However, i1 'to i5': current of each series resistor Ra1 to Ra5 i1 to i5: current of each digit adjusting resistor ra1 to ra5 As described above, the starting resistor Ra0 is directly connected between the terminals I1 and O1 without using a switch as described above. Connected, and this current is
Set to 0.

Accordingly, the resistance network R flowing through the output terminal O1
The current ia of M1 is represented by the following equation (2).

[0023]

[Number 2] ia = i0 + i1 + i2 + i3 + i4 + i5 = i0 + i1 × 5 Σ x = 1 A X · 2 - (x-1) ·· (2) = (Vg - -Vg +) / Ra0 + ^[(Vg - -Vg ⁺⁾ / 2.rho _{1] ^{× 5 Σ x = 1 a X}} · 2 - (x-1) ·· (3) where a _X (x = 1~5) were generally represents a switch Sa1~Sa5 the parameter x Sax (x = 1 to
5) When the terminal O1 side A _X = 1, when the terminal A1 side A
_X = 0.

The first term of the equation (3) is the switches Sa1 to Sa
5 is a constant current unrelated to the selection switching, and the second term can be changed in the range of the following equation (4) by selecting the connection of the switches Sa1 to Sa5.

[0025]

Equation 3] 0 ^{<[(Vg - -Vg +) / 2ρ} 1 ] _{^{× 5 Σ x = 1 A X}} · 2 - (x-1) <(31/32) · (Vg - -Vg +) / ρ ₁ ... (4) The minimum unit of this current change is expressed by the following equation (5).

[0026]

(1/32) · (Vg ⁻ −Vg ⁺ ) / ρ ₁ = (1/2 ⁵ ) · (Vg ⁻ −Vg ⁺ ) / ρ ₁ (5) That is, with five switches ^2-5 resolution adjustment is possible. Similarly, the current ib flowing through the output terminal O2 of the resistance network RM2 is expressed by the following equation (6). Note that the resistance network RM2
Is similar to the configuration of the resistance network RM1 in this example.
Only the constituent means, the resistance value, and some of the signs (symbols) of the applied voltage are different.

That is, in the resistance network RM2, the resistance network RM
Input terminal voltage Vg at 1 ^- to the Vcc, starting resistor R
a0 is Rb0 and unit series resistances Ra1 to Ra4 are Rb1.
The ～Rb4, the termination series resistor Ra5 is Rb5, digits by adjusting resistor ra1~ra5 is Rb1～rb5, the resistance value [rho ₁ is [rho _2, the switch Sa1~Sa5 is SB1 to SB5,
Replace each one.

[0028]

Equation 5] ^{ib = (Vcc-Vg +)} / Rb0 + ^{[(Vcc-Vg +) / 2ρ} 2 ] _{^{× 5 Σ y = 1 B y}} · 2 - (y-1) ·· (6) where B _y (y = 1 to 5) is a switch Sby that generally represents the switches Sb1 to Sb5 by the parameter y.
When (y = 1 to 5) is on the terminal O2 side, B _y = 1 and the terminal A2
On the other hand, B _y = 0.

Similarly, the current ic flowing through the output terminal O3 of the resistance network RM3 is expressed by the following equation (7). Note that the configuration of the resistance network RM3 is the same as the configuration of the resistance network RM1 in this example, and only the configuration means, the sign (symbol) of the resistance value, and a part of the applied voltage are different. That input terminal voltage Vg of the resistor network RM3 the resistor network RM1 ^- to 0, the starting resistor Ra0 is Rc0, the unit series resistance Ra1~Ra4 is R
c1 to Rc4, the termination series resistor Ra5 to Rc5, the digit-by-digit adjustment resistors ra1 to ra5 to rc1 to rc5, and the resistance value ρ
To ₁ ρ _3, switch Sa1~Sa5 is Sc1~Sc5
, Respectively.

[0030]

[6] ic = (- 1) × Vg + / Rc0 + ^{[(- 1) × Vg + /} 2ρ 3 ] _{^{× 5 Σ z = 1 C z}} · 2 - (z-1) ··· (7) Here, C _z (z = 1 to 5) is a switch Scz that generally represents the switches Sc1 to Sc5 by the parameter z.
When (z = 1 to 5) is on the terminal O3 side, C _z = 1, terminal A3
On the side, C _z = 0.

The output voltage of the operational amplifier OP1 is the output voltage Vout of the semiconductor pressure transducer, and is represented by the following equation (8).

[0032]

Equation 7] ^{Vout = Vg + - (ia +} ib + ic) × Rf = Vg + + (Vg + -Vg -) × [(Rf / Ra0) + (Rf / 2ρ 1) × 5 Σ x = 1 A X · 2 - ^(x-1)] - (Vcc-Vg ⁺⁾ × [(Rf / Rb0) + (Rf / 2ρ 2) × 5 Σ y = 1 B y · 2 - (y-1) ] + Vg ⁺ × [(Rf / Rc0) + (Rf / 2ρ 3) × 5 Σ z = 1 C z · 2 - (z-1) ] (8) where (Vg ⁺ -Vg ^-) is a strain gauge bridge differential Output Vg. For the sake of simplicity, assuming that one-side output Vg ⁺ of the strain gauge bridge is Vcc / 2 when the pressure is zero, and that the change in Vg ⁺ due to pressurization is sufficiently small compared to Vcc / 2, equation (8) Can be approximated as in the following equation (9).

[0033]

Vout {Vg × Rf [(1 / Ra0) + (1 / 2ρ ₁ ) × ⁵ _{} x = 1} A _X −2− ^(x−1) ] + (Vcc / 2) × Rf × [− (1 / Rb0) - (1 / 2ρ 2) × 5 Σ y = 1 B y · 2 - (y-1) + (1 / Rc0) + (1 / 2ρ 3) × 5 Σ z = 1 C z · 2- ^(z-1) ] + (Vcc / 2) (9) The first term on the right side of the equation (9) is the pressure transducer output voltage Vou.
t is the pressure signal voltage component during t, and the switches Sa1 to Sa
By selecting the connection of 5, it is possible to change the coefficient value of the differential output Vg of the strain gauge bridge and thus the sensitivity of this pressure transducer. The second term on the right side of the equation (9) is an offset voltage component, and the switches Sb1 to Sb5
And the connection of Sc1 to Sc5, it is possible to change the value of this offset component, that is, the zero-point potential of the output voltage Vout in both positive and negative directions.

Switches Sa1 to Sa5, Sb1 to Sb
5, Sc1 to Sc5 are composed of analog switches, current switches, and the like, and can be integrated using transistors.
The switch is driven by a drive signal obtained by converting a serial signal, a BCD signal or the like from outside the pressure transducer into a parallel binary signal by a decoder in the pressure transducer.

In order to provide a function equivalent to the conventional trimming of a resistor by selecting the connection of the switch,
The driving states of these switches are EPROM, E ² PRO
The circuit configuration is such that data is stored even when the power is off by using an M, a zener zap, a fuse (including an antifuse), and the like. The entire circuit of the above pressure transducer can be integrated on the same or a plurality of chips by using a diffusion resistor or a thin film resistor as a resistor. Of course, hybrid ICs including thick or thin resistive substrates
It can also be realized as

(Embodiment 2) FIG. 3 shows a circuit configuration as a second embodiment of the present invention. In this figure, temperature-compensating resistance networks RM4 and RM5 are provided in parallel with the resistance networks RM2 and RM3, respectively, as compared with FIG. 1, and the feedback resistance of the operational amplifier OP1 is replaced by a resistance Rft having a large positive temperature dependency. Has been replaced.

Here, the resistor network RM4 is formed of an input terminal I4 and a current bypass terminal A4 in order from the input terminal I4 side. In this example, the unit series resistances Rd1 to Rd4 and the terminal series resistance R
d5, and each series resistor Rd1.
Digit-by-digit adjustment resistors rd1 to rd5 each having one end connected to the input terminal I4 side terminal of Rd5;
Switches Sd1 to Sd5 are set in advance so that the other ends of d1 to rd5 are respectively switched to the output terminal O4 side or the current bypass terminal A4. Further, the resistance value of each unit series resistor Rd1 to Rd4 is ρ ₄ , and the resistance value of the terminal serial resistor Rd5 in the final stage and the adjustment resistor rd1 to rd5 for each digit is 2ρ ₄ .

Similarly, the resistor network RM5 includes a start-point series resistor Ret composed of, for example, a diffused resistor, which has a large temperature dependency and is provided between the input terminal I5 and the current bypass terminal A5 in order from the input terminal I5 side. In this example, the unit series resistances Re1 to Re4 and the terminal series resistance R
e5 and the series resistors Re1 to
Digit-by-digit adjustment resistors re1 to re5 each having one end connected to a terminal on the input terminal I5 side of Re5;
Switches Se1 to Se5 are set in advance so that the other ends of e1 to re5 are respectively switched to the output terminal O5 side or the current bypass terminal A5. The resistance value [rho ₅ of the unit series resistance Re1～Re4, also the resistance of the terminating series resistor Rq5 and each digit by adjusting the resistance re1~re5 the final stage and 2.rho _5.

Next, the operation of the circuit shown in FIG. 3 will be described. The current id1 flowing through the digit-by-digit adjustment resistor rd1 is expressed by the following equation (10).

[0040]

Equation 9] ^{id1 = (Vcc-Vg +)} / 2 (Rdt + ρ 4) ··· (10) Thus the current flowing through the output terminal O4 of the resistor network RM4 i
d is represented by the following equation (11).

[0041]

Equation 10] id = ^{[(Vcc-Vg +) / 2} (Rdt + ρ 4) ] _{^{× 5 Σ m = 1 D m}} · 2 - (m-1) ··· (11) where D _{m (m} = 1 To 5) are switches Sdm that generally represent the switches Sd1 to Sd5 by the parameter m.
When (m = 1 to 5) is on the terminal O4 side, D _m = 1 and the terminal A4
D _m = 0 at the side.

Similarly, the current ie flowing through the output terminal O5 of the resistance network RM5 is expressed by the following equation (12).

[0043]

Equation 11] ie = (- 1) × ^{[Vg + / 2 (Ret + ρ} 5) ] _{^{× 5 Σ n = 1 E n}} · 2 - (n-1) ··· (12) where E _n (n = 1-5) are switches Sdn that generally represent the switches Se1-Se5 by the parameter n.
(N = 1 to 5) is E _n = 1 when the terminal O5 side terminal A5
On the side, _En = 0.

Here, using the same approximation as in the first embodiment, and further adding the pressure signal and the zero point potential by the resistance network RM1 to RM3, the output voltage Vout of this semiconductor pressure converter is obtained.
Is obtained as shown in Expression (13).

[0045]

Equation 12] ^{Vout = Vg + - (ia +} ib + ic + id + ie) × Rft ≒ Vg × Rft [(1 / Ra0) + (1 / 2ρ 1) × 5 Σ x = 1 A X · 2 - (x-1) ] + ( vcc / 2) × Rft × [- (1 / Rb0) - ( 1 / 2ρ 2) × 5 Σ y = 1 B y · 2 - (y-1) + (1 / Rc0) + (1 / 2ρ 3) × ⁵ Σ _{z = 1} C _z · 2- ^(z-1) ] + (Vcc / 2) × (Rft / 2) × [-[1 / (Rdt + ρ ₄ )] × ⁵ Σ _{m = 1} D _m · 2 ^- the ^(n-1)] + (Vcc / 2) ··· ( 13) this equation ^{(13) - (m-1} ) + [1 / (Ret + ρ _{5)] ^{× 5 Σ n = 1 E n}} · 2 The first term on the right side is the pressure sensitivity component, the second term,
The third term is an offset component. Normally, the output voltage Vg of the semiconductor strain gauge has a negative temperature dependency, which is compensated for by the positive temperature dependency of the feedback resistor Rft to compensate for the sensitivity temperature characteristic.

The output voltage of the pressure transducer when the pressure is zero,
That is, with respect to the temperature characteristic of the zero-point potential, the first term on the right side of the equation (13) (when the pressure is zero, the semiconductor strain gauge output voltage Vg of the first term is not always 0) and the temperature characteristic of the second term vary. RM4, RM5
Of the switches Sd1 to Sd5, Se1 to Se5, and the third term D _m (D1 to D5),
By choosing the values of E _n (E1~E5), the right side third
It is possible to compensate for the temperature dependency of the term by canceling out the temperature dependency of the first and second terms on the right side.
As described above, according to the second embodiment, it is possible to realize a semiconductor pressure transducer having not only the function of adjusting the sensitivity and the zero-point potential but also the function of compensating the temperature characteristics of the sensitivity and the zero-point potential.

In order to compensate the sensitivity temperature characteristic, a method of inserting a resistor having a large temperature dependency between the input terminal I1 of the resistance network RM1 and the series resistance circuit in addition to the above-described method is used. It can also be used. Apart from the above method, the starting resistor Ra0 of the resistor network RM1 to RM3 in FIG.
By configuring .about.Rc0 in combination with a resistor having a large temperature dependency, it is possible to compensate for the temperature characteristics of sensitivity and zero potential.

[0048]

According to the present invention, at least a plurality of unit series resistors (Ra1 to Ra4, etc.) and a terminating series resistor (Ra) are used.
5) having one or more digitized adjusting resistors (ra1 to ra5, etc.) selected from switches at the other end by switches (Sa1 to Sa5, etc.). A resistance network (RM1 to RM5, etc.) is provided in a signal processing circuit for amplifying and adjusting the output signal Vg of the strain gauge bridge, and the connection of the adjustment resistor for each digit is selected by a digital signal supplied from the outside, thereby
Since the output current of the resistor network is variably set at a resolution of 2 ^-n (where n is the number of switches), the sensitivity of the output voltage of the semiconductor pressure transducer and the zero-point potential can be adjusted. The following effects can be obtained as compared with the method of performing the above. (1) Since the circuit adjustment can be performed instantaneously with a digital signal, it is not necessary to align a chip or a circuit board for the adjustment, and the time required for the adjustment can be greatly reduced. (2) Even after the chip or the circuit board is mounted, the adjustment can be performed by inputting the digital signal for adjustment to the input terminal of the package, so that there is no fear that the chip or the circuit board becomes dirty or damaged. (3) The circuit including the operational amplifier OP1 that adds the current for adjustment from the resistance network and converts it into a voltage also has the functions of amplifying the pressure signal output from the strain gauge bridge and converting the impedance, and as a result, the number is small. A pressure transducer that can be adjusted by a digital signal with the number of elements can be realized.

The output signal Vg of the strain gauge bridge
The feedback resistance of the operational amplifier OP1 for amplifying the input signal includes a feedback resistance Rft having a large positive temperature dependency, a starting series resistance Rdt and Ret having a large temperature dependency, and the like. Since the resistor networks RM4, RM5 and the like that can adjust the current are used (claims 3 to 5), the sensitivity temperature characteristic and the zero-point potential temperature characteristic of the pressure transducer output voltage can be easily compensated, and a wide range can be obtained. A semiconductor pressure transducer for applications requiring high accuracy in a temperature range can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration as a first embodiment of the present invention;

FIG. 2 is an explanatory diagram of a resistance network RM1 in FIG. 1;

FIG. 3 is a circuit diagram showing a configuration as a second embodiment of the present invention;

FIG. 4 is an explanatory diagram of conventional resistor trimming.

[Explanation of symbols]

RG1~RG4 semiconductor strain gauges G1, G2 strain gauge bridge output terminal Vcc supply voltage Vout semiconductor pressure transducer output voltage Gnd ground potential Vg ^+, Vg ^- strain gauge bridge side output potential Vg strain gauge bridge differential output voltage OP1 to OP3 Operational amplifier Rf Feedback resistor Rft Feedback resistor having a large positive temperature dependency RM1 to RM5 Resistive network I1 to I5 Input terminal of resistive network O1 to O5 Output terminal of resistive network A1 to A5 Current bypass terminals Ra0 to Rc0 Starting end resistors Rdt, Ret Resistances with large temperature dependence (starting end series resistances) Ra1 to Ra4, Rb1 to Rb4, Rc1 to Rc4, R
d1 to Rd4 Re1 to Re5 Unit series resistance Ra5, Rb5, Rc5, Rd5, Re5 Termination series resistance ra1 to ra5, rb1 to rb5, rc1 to rc5, r
d1 to rd5 re1 to re5 Digit-based adjustment resistors Sa1 to Sa5, Sb1 to Sb5, Sc1 to Sc5, S
d1 to Sd5 Se1 to Se5 switches ρ ₁ , ρ ₂ , ρ ₃ , ρ ₄ , ρ ₅ resistance values

Claims (5)

[Claims] 1. A plurality of strain gauges formed and arranged on a silicon diaphragm by diffusion, given a predetermined power supply voltage and a ground potential to respective predetermined terminals, and a strain gauge generated in accordance with a pressure applied to the diaphragm. A current corresponding to the output voltage is supplied to a feedback resistor connecting the inverting input terminal and the output terminal to convert the current into a voltage, and an operational amplifier is provided as an output voltage of the semiconductor pressure transducer. In a semiconductor pressure transducer provided with a signal processing circuit for performing amplification and adjustment on the same or a plurality of silicon chips that can include a resistance substrate, the signal processing circuit includes first, second, and third signals, respectively. A first network terminal having a fixed or variable potential present or occurring in the semiconductor pressure transducer, said second or third network terminal; One of a predetermined potential or a plurality of potentials different from the input potential is input, a second network terminal is connected to an inverting input terminal of the operational amplifier, and a third network terminal is a second network terminal. A resistor network connected at a potential substantially the same as that of the operational amplifier and independent of the operational amplifier, wherein at least a first network is connected between a first network terminal and a third network terminal. A resistor series circuit in which a plurality of unit series resistors having the same resistance value in order from the terminal side and a terminating series resistor having a resistance value twice the unit series resistance are connected in series one by one; Each of the plurality of unit series resistors and the terminating series resistor has, at one end on the first network terminal side, one end of a digit-by-digit adjustment resistor having a resistance value that is twice the unit series resistance in a one-to-one relationship. Is connected, and the other end of each digit adjustment resistor is connected to the second or One or more resistor networks selectively connected to any one of the third network terminals; and selectively adjusting digit-by-digit adjustment resistors of each of the resistor networks in response to an external digital signal. Selective connection means for making a proper connection even when the power supply is lost, and selectively connecting to the second network terminal of each of the resistor networks at the inverting input terminal of the operational amplifier. The semiconductor pressure transducer is characterized in that currents input from the digitized adjustment resistors are added, converted into a voltage by the feedback resistor, and superimposed on the output voltage of the semiconductor pressure transducer. 2. The semiconductor pressure transducer according to claim 1, wherein a potential input to said first network terminal is output from a strain gauge generated according to said pressure, or said output potential is subjected to signal processing. Any one of the potential corresponding to the output potential, the power supply voltage, and the ground potential, and the sensitivity of the output voltage of the semiconductor pressure transducer to the pressure signal of the strain gauge or (and) the zero potential is converted to the external digital signal. A semiconductor pressure transducer characterized in that it can be adjusted accordingly. 3. The semiconductor pressure transducer according to claim 1, wherein the feedback resistor includes a resistor having a large positive temperature dependency, and compensates for the sensitivity temperature characteristic of the output voltage of the semiconductor pressure transducer. Semiconductor pressure transducer. 4. A semiconductor pressure transducer according to claim 1, wherein a first network terminal of at least one of the resistance networks or a plurality of resistance networks and a resistance series circuit. And a series resistor having a large temperature dependency is inserted in series between them so as to compensate for the sensitivity temperature characteristic of the output voltage and / or the temperature characteristic of the zero point potential of the semiconductor pressure transducer. Semiconductor pressure transducer. 5. The semiconductor pressure transducer according to claim 1, wherein a first network terminal of at least one or a plurality of resistance networks of said resistance networks and a second network terminal are connected to each other. A temperature-dependent starting resistor is inserted between the terminal and the network terminal to compensate for the sensitivity temperature characteristic of the output voltage and / or the zero-point potential temperature characteristic of the semiconductor pressure transducer. Semiconductor pressure transducer.