JPH03254217A - Semiconductor sensor - Google Patents

Abstract

PURPOSE:To realize the sensor with one semiconductor chip, to improve the mass- productivity of semiconductor sensors and to reduce the cost by realizing a circuit amplifying a minute detection voltage of a sensor section, and digitizing the amplified output with the combination of CMOS inverters being fundamental integrated circuits. CONSTITUTION:A sensor section SEN outputting a detection voltage in response to a measured physical quantity, a CMOS inverter IV amplifying the detected voltage, and threshold level generating circuits 20-22 in which output terminals of CMOS inverters each having an ON resistance corresponding to the weight of bits are connected in common, a voltage corresponding to each bit of prescribed digital information is given to input terminals and a threshold voltage corresponding to the digital information is outputted from the output terminals are provided to the sensor. Moreover, an A/D converter circuit is provided, which compares and discriminates an output voltage of the CMOS inverter IV with a threshold voltage generated from the threshold level generating circuits 20-22 and outputs the result of comparison as digital information corresponding to the measured physical quantity. Then they are formed on a same semiconductor substrate. Thus, the semiconductor sensor with simple constitution and excellent mass-productivity is realized.

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention is applicable to semiconductor sensors suitable for use, for example, in industrial manufacturing equipment, measuring instruments, the automobile industry (car electronics), medical equipment such as blood pressure monitors, or sensors such as watches and vacuum cleaners. Regarding. "Prior Art" Various sensors using semiconductor materials are generally small, lightweight, and highly sensitive, and have the advantage of being able to sense many physical quantities, and have been widely put into practical use. However, from the opposite perspective, semiconductor materials are easily affected by physical quantities such as light, temperature, humidity, and pressure, and generally when measuring the required physical quantity as a sensor output, accurate measurement is affected by the influence of other physical quantities. However, when mass-producing the sensor, slight variations in the manufacturing process tend to lead to variations in the characteristics of the sensor as a final product. For this reason, when used as a pressure sensor, for example, conventionally the temperature characteristics are compensated to eliminate the influence of temperature, or the sensor output is amplified by an operational amplifier mounted on a hybrid IC to adjust the sensitivity. Countermeasures have been taken, such as using a trimming resistor to compensate for the signal. However, this method requires trimming for each sensor, which has drawbacks in terms of mass production and cost. Against this background, semiconductor sensors in which a sensor and a signal processing circuit are monolithically integrated into one semiconductor chip have recently been developed. ``Problems to be Solved by the Invention'' However, the semiconductor sensor in which the above-mentioned sensor and signal processing circuit are made monolithic uses an operational amplifier as the semiconductor amplification circuit, and generally has a complex circuit configuration and has poor characteristics. It is affected by the values of passive elements such as resistive elements and capacitive elements added to operational amplifiers, making integration difficult, and currently there is no significant effect in terms of improving mass productivity or reducing costs. Not only for pressure sensors but also for other sensors, when detecting physical quantities where the signal strength is too weak to obtain a high signal-to-noise ratio, various countermeasures are required to increase sensitivity and eliminate noise. There are problems in terms of performance and cost.In addition, these sensors have been applied to a wide range of fields recently, and the characteristic specifications required of the sensors have become diverse depending on the purpose of use. It has become difficult to provide a sensor that can satisfy the above-mentioned problems.This invention was made in view of the above problems.
An object of the present invention is to provide a semiconductor sensor capable of obtaining digital information corresponding to a physical quantity to be measured, which is realized by one semiconductor chip, has a simple configuration, and is excellent in mass production. "Means for Solving the Problems" The present invention includes a detection unit that outputs a detection voltage according to a physical quantity to be measured, a CMOS inverter that amplifies the detection voltage ffJ, and an on-resistance that each corresponds to the weight of the bit. CMOS with
The output terminals of the inverters are connected in common, and the input terminal of each CMOS inverter is given a voltage corresponding to each bit value of predetermined digital information, and the output terminal of the commonly connected output terminal is applied with a voltage corresponding to each bit value of the digital information. at least one threshold generation circuit that outputs a voltage, and comparing and determining the output voltage of the CMOS inverter with the threshold voltage generated by the threshold generation circuit, and using the comparison result as digital information corresponding to the physical quantity to be measured. The device is characterized in that the output analog/digital conversion circuit is formed on the same semiconductor substrate. "Operation" According to the above configuration, the detected voltage according to the physical quantity to be measured is C
After being amplified by the MOS input, the amplified output is compared and determined with a threshold voltage generated by a threshold circuit, and the comparison result is output as digital information corresponding to the physical quantity to be measured. "Embodiments" Hereinafter, the present invention will be described in detail with reference to the drawings.

First Embodiment FIG. 1 is a block diagram showing the configuration of a semiconductor sensor according to a first embodiment of the present invention. In Figure 1, SEN is a sensor unit that generates a detection voltage according to the physical quantity to be measured;
v is a CMO used as an amplifier to amplify the detection voltage
It is an S inverter. Figure 2 shows the sensor section SEN and CMOS inverter IV.
shows. The sensor section SEN is formed by connecting resistive elements R1 and R9 in series between the power supply VDD and the ground line, the resistance of which changes depending on the physical quantity to be measured. Examples of this type of resistance element include resistance temperature sensors (
Thermistors), piezoresistive elements used in pressure sensors or acceleration sensors, and various photoelectric conversion elements are known. In the sensor unit SEN, the resistance value of resistance element R1 and the resistance value of resistance element R2 change in opposite directions with respect to changes in the physical quantity to be measured, and the potential at the connection point M between resistance elements R1 and R7 changes with respect to the change in the physical quantity to be measured. Changes depending on physical quantity. This means that, for example, when applying this embodiment to a pressure sensor, piezoresistive elements are created as resistance elements R1 and R2,
At this time, this can be achieved by arranging each element so that the direction of strain is reversed. Note that it is not necessary for both resistance elements R2 and R7 to have resistance values that change depending on the physical quantity to be measured. One of the resistors may be a fixed resistor. Fluctuations in the potential at the connection point M are amplified by the CMOS inverter IV, and an amplified output V out is obtained. FIG. 3 illustrates the human output characteristics of the CMOS inverter rv. The resistance ratio of the resistive elements R1 and R7 is set in a continuous window so that the voltage obtained at the connection point M falls within an input voltage range AR in which a relatively linear output change is obtained with respect to an input change. 10 to 12 and 20 to 22 in FIG. 1 are each D/
A conversion circuits 30 to 32 are each D/A conversion circuit lO
And 20.11 and 21,! This is a synchronous comparator that compares the magnitude of each output voltage of 2 and 22. D/A in Figure 4
An example of the configuration of conversion circuits IO-1220-22 is shown. In FIG. 4, rVo to IV are CMOS inverters, and each input terminal receives the 0th bit (weight 2°), the 1st bit (weight 2'), and the 2nd bit (weight 2°) of the digital information.
is input, and each output terminal is commonly connected to form an analog output terminal Y. These CMOS inverters IVo
~IV, are the human weights 2° and 2, respectively.
It has an on-resistance inversely proportional to ',2'. Such adjustment of on-resistance is necessary for P, N, which constitutes a CMOS inverter.
This can be easily implemented by adjusting the channel width or channel length of each transistor. According to such a configuration, each bit X of input digital information. −
An analog voltage Σai−Xi (where ai is a weighting coefficient corresponding to Xi) of 1°O is outputted from the analog output terminal Y by weighting X. In FIG. 1, the output voltage of a CMOS inverter IV is input to the digital input terminals X0 to X of the D/A conversion circuits IO to 12. The respective outputs of the D/A conversion circuits 10-12 are inputted to the input terminals A of the comparators 30-32, respectively. The D/A conversion circuit 22 has digital input terminals X,,X,. Voltages corresponding to the logical values "1", "0", and "0" are respectively input to Xo, and an analog voltage corresponding to the digital information 100 is generated and supplied to the input terminal B of the comparator 32 as a threshold voltage. A2 as the output of comparator 32
When A is B, "I" is output, and when A<B, "0" is output as the second bit output to output terminal Q. Further, the output of the comparator 32 is supplied to the digital input terminals X, and the D/A conversion circuit 21 has the digital input terminals X, , X
A voltage corresponding to the logical value "l"Oo is input to each of the voltages o. The output of the D/A conversion circuit 21 is supplied to the input terminal B of the comparator 31, and the output of the comparator 31 is outputted as the first bit output to the output terminal Q. Further, the D/A conversion circuit 20 has its digital input terminal x1Xl supplied with each output value of the comparators 32 and 31, and its digital input terminal X0 with a voltage corresponding to the logical value "1". The output of the D/A conversion circuit 20 is supplied to the input terminal B of the comparator 30, and the output of the comparator 30 is supplied to the output terminal Q as the 0th bit output. is output to. Below, digital information 101 from CMOS inverter Iv
The operation of this semiconductor sensor will be explained using an example in which an analog voltage corresponding to t is output. The output of the CMOS inverter rv is sent to the D/A conversion circuit 10.
-12, is amplified to a level matching the threshold values generated by the D/A conversion circuits 20-22, and is output from each output terminal Y of the D/A conversion circuits 10-12. In the comparator 32, the output voltage of the D/A conversion circuit 12 and the D
A threshold voltage corresponding to the digital information 100 output from the /A conversion circuit 22 is compared. As a result, the comparator 32 outputs "I" as the comparison result, which is output as the second bit output to the output terminal Q. In the D/A conversion circuit 21, the output of the comparator 32 is "I".
1", a threshold voltage corresponding to the digital information 110 is generated. As a result, the comparator 31 outputs "O" as the comparison result, which is output to the output terminal Q as the first bit output. , in the D/A conversion circuit 20, since the output of the comparator 32 is "1" and the output of the comparator 31 is "0", a threshold voltage corresponding to the digital information 101 is generated. When the output voltage is even slightly higher than the digital information 101, comparator 3
From 0, "1 degree" is output as a comparison result, and when the voltage value is even slightly lower, "0" is output, and the output end Q is output as the 0th bit power. is output to. In this way, analog voltages output from the D/A conversion circuits 10 to 12 are successively compared with threshold voltages according to physical quantities to be measured, and the analog voltages are sequentially converted into digital information starting from the MSB. The same operation as described above is performed even when other voltage values are output from CMOS inverter IV.

Second Embodiment FIG. 5 is a block diagram showing the configuration of a semiconductor sensor according to a second embodiment of the present invention. In addition, in FIG. 1, the same reference numerals are given to the parts corresponding to those in FIG. In Fig. 5, U,,Vo,[J,,V,,U,,V
, are each CMOS inverters, and the first stage C
Both MOS inverters U0 to U have thresholds equal to the power supply voltage V.
It is designed to fit around 1/2 of DD. 40 and 4I are each 4-bit D/A conversion circuits, which are constructed by additionally connecting a CMOS inverter having an output on-resistance corresponding to the third bit (23) to the configuration shown in FIG. ing. The output Vx of the CMOS inverter Iv is the CMOS
The level is determined through inverters U and V, and the determination result is outputted to output terminal Q as a second bit output. The D/A conversion circuit 41 has a digital input terminal X,
The output of the CMOS inverter 1v is input to the digital input terminal X, the output of the CMOS inverter V is input to the digital input terminal X, and voltages corresponding to 1" and "0" are input to the digital input terminals Xl and Xo, respectively. , D/A conversion circuit 4
1, the above-mentioned weighted addition of these input voltages is performed, and a voltage corresponding to the addition result is output from the D/A conversion circuit 41. And the D/A conversion circuit 4I
The level of the output is determined by passing through the CMOS inverter U and vl, and the determination result is outputted to the first bit output terminal Q1. Similarly, for the 0th bit, the CMOS inverter IV
The bit value is determined based on Vx and the determination results of the second and first bits. [Third Embodiment f141] FIG. 6 is a block diagram showing the configuration of a semiconductor sensor according to a third embodiment of the present invention. In this figure, the same reference numerals are given to the parts corresponding to those in FIG. In FIG. 6, UA, VA, UC, and VC are each C
Both of the first-stage CMOS inverters UA and UC are MOS inverters, and the threshold value is 1/1 of the power supply voltage VDD.
It is designed to be around 2. UB is an EXOR gate. 50 and 51 are 4-bit D/A conversion circuits having the same configuration as that used in the second embodiment. The D/A conversion circuit 51 has a CMOS at the digital input terminal X.
are input to the output V of the inverter IV, and the digital input terminals X t, X 1. x o has “l”, “0”,
A voltage corresponding to "0" is input. Further, the D/A conversion circuit 50 has the output Vx of the CMOS inverter v inputted to the digital input terminal X3, and the digital input terminals X, , X,
,
If the range of is 0 to l, when VW<3/8, "1" is output only from output terminal C, and Vx is 3/8 to 4/8.
When , "l" is output only from output terminal B, and Vx>4
At the time of 78, "1" is output only from the output terminal A. This embodiment is useful when a physical quantity to be measured, such as temperature or pressure, is controlled within a certain range and only that range is digitized. For example, if the physical quantity to be measured is temperature, then A is 1
When , the temperature is too high, and when C is 1, the temperature is too low. Bh
It is also possible to use it to achieve an appropriate temperature when <1. "Effects of the Invention" As explained above, the semiconductor sensor according to the present invention has
A circuit that amplifies the weak detection voltage of the sensor section and converts the amplified output into a digital signal is realized by introducing a CMOS inverter, which is the basic circuit of the latest integrated circuit. Therefore, it can be realized with one semiconductor chip, which has the effect of improving the mass productivity of semiconductor sensors and reducing costs.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a semiconductor sensor according to the first embodiment of the present invention, FIG. 2 is a diagram showing the sensor section SEN and CMOS inverter IV in the first embodiment, and FIG. 3 is a diagram showing the configuration of the semiconductor sensor according to the first embodiment. A diagram illustrating the human output characteristics of CMOS inverter IV, FIG. 4 is a D/A in the same example.
A circuit diagram showing a configuration example of a conversion circuit, FIG. 5 is a block diagram showing a configuration of a semiconductor sensor according to a second embodiment of the present invention,
FIG. 6 is a block diagram showing the configuration of a semiconductor sensor according to a third embodiment of the present invention. S E N-=-sensor section, IV, IVo, IV,, r
V.・・CMOS inverter, 20-22, 40, 4150
．． 51...D/A conversion circuit, 30-32...Comparator

Claims (1)

[Scope of Claims] A detection unit that outputs a detected voltage according to a physical quantity to be measured, and a CMOS inverter that amplifies the detected voltage, each of which includes:
The output terminals of CMOS inverters having on-resistances corresponding to the weights of the bits are connected in common, and the input terminals of each CMOS inverter are given voltages corresponding to each bit value of predetermined digital information, and the commonly connected at least one threshold generation circuit that outputs a threshold voltage corresponding to the digital information from an output terminal thereof, and compares and determines the output voltage of the CMOS inverter with the threshold voltage generated by the threshold generation circuit, and calculates the comparison result. and an analog/digital conversion circuit that outputs the physical quantity as digital information corresponding to the physical quantity to be measured, the semiconductor sensor being formed on the same semiconductor substrate.