JPS6120802B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature detection circuit configured in a semiconductor integrated circuit.

Conventionally, for example, electronic watches use a crystal oscillator with a large Q value as a time standard, and the circuits such as the oscillation circuit of the crystal oscillator, the oscillation frequency dividing circuit, and the drive circuit that drives the time display are all made of the same semiconductor. In particular, an N-type silicon substrate has been used as the semiconductor substrate, and complementary field effect transistors have been integrated and used as the elements, considering the advantage of low power.

However, recently, in order to improve the accuracy of electronic watches, there has been an increasing demand for controlling the oscillation frequency of crystal resonators, which are temperature dependent. On the other hand, as electronic watches are required to be smaller, thinner, and lower in cost, the temperature compensation of the oscillation circuit has been replaced by BaTiO ₃ capacitors, thermistors, etc., which have opposite temperature characteristics to conventional crystal oscillators. Configure the oscillation circuit
There is an increasing demand for configuring means for correcting temperature characteristics on the IC board, instead of using external means independent of the IC board. In order to realize a means of temperature compensation on such an IC board, it is necessary to
Although an element for detecting temperature is required on the substrate, normally in a semiconductor integrated circuit, only the configuration of transistors, capacitors, diodes, and resistors can be integrated on the semiconductor integrated circuit. In view of these points, the present invention relates to a circuit in which a means for detecting temperature on a semiconductor integrated circuit is constructed using elements such as transistors and diodes.

Conventionally, various types of temperature detection circuits configured on semiconductor integrated circuits have been considered, but they have the disadvantage that the detection voltage varies depending on the power supply voltage, making it difficult to actually use the circuit. This was a major hindrance when operating the system. Furthermore, even if the temperature dependence of the voltage between the base and emitter of a transistor is used as a temperature detection element,
There is an absolute dependence on temperature when considering various factors such as resistance variation when configuring a circuit as a semiconductor integrated circuit and mass producing it. It is very difficult to capture this, as in the case of mass production,
If it is difficult to adjust each element one by one, temperature detection is almost impossible.

From this point of view, the present invention has no dependence on fluctuations in power supply voltage, and furthermore, does not depend on fluctuations in absolute quantities of elements as in the case of IC mass production processes. The device is configured to detect the amount relative to the minute.

Embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 shows a specific example of a conventional temperature detection circuit, in which temperature detection is performed using the temperature dependence of the voltage V _BE between the base and emitter of 116 transistors. 111-1 in the figure
15 represents the resistance necessary to determine the bias point of the field effect transistor 116, and each
It has resistance values of R ₁ , R ₂ , R ₃ , R ₄ , and R ₇ . Further, 117 represents a detection voltage output section. Considering that the current I _E flowing through the resistor 114 is I _E =V-V _BB -V _BE /R ₄ , the detection voltage Vo of this circuit is V ₀ =R ₇ /R ₄ (V-V _BB − V _BE ). Here, V _BB represents the base bias point voltage, and assuming that the base current flowing through R ₃ is sufficiently small compared to the current flowing through R ₂ and R ₁ , V _BB = R ₂ V/R ₁ + _R2 . Therefore, the voltage output of 117 becomes V ₀ =R ₇ /R ₄ (R ₁ /R ₁ +R ₂ V-V _BE ). However, as is clear from this equation, assuming that the temperature dependence dV ₀ /dT of the output voltage V ₀ does not vary depending on the power supply voltage V, dV ₀ /dT=-R ₇ /R ₄ dV _BE / dT, and the variation of V _BE is 114 and 11
It will be expressed as a ratio of low resistance of 7. However, in actual cases, fluctuations in the power supply voltage often occur, such as attenuation during the life of a battery in an electronic watch.

Therefore, it is extremely difficult to capture accurate temperature fluctuations as the output of V ₀ . Furthermore, in this example, in order to construct the resistors 114 and 115 on the semiconductor integrated circuit board, they are made by thermally diffusing P ^- etc. on the N ^- substrate. Considering processes such as thermal diffusion, 11
It is extremely difficult to manufacture a device with absolute resistance values such as 4,155 without variations between elements. Furthermore, even if the resistance value is controlled by the relatively easy-to-control ion implantation process on the semiconductor integrated circuit, it is very difficult to create an accurate value, and the voltage change due to temperature fluctuation dV _BE /dt Since a large change appears in the coefficient R ₇ /R ₄ , it is expected that an even larger change will occur together with the power supply voltage change, making the configuration of a semiconductor integrated circuit even more complicated.

The present invention eliminates these drawbacks, and FIG. 2 shows one embodiment thereof. 2 in the diagram
11-214 are field effect transistors, 215-
217 represents a resistance, and 218 represents an output. The operation of this circuit will now be explained in detail. 2
11, 212, and 217 are bias circuits that determine the reference potential Vs connected to the field effect transistor 214, and the potential of 219 is the same as that of 211 and 21.
2 are equal, and the threshold voltage is V _THp
1 , V _THo1 , then Vs(V−V _THp1 +V _THo
1 )/2. Also, due to the resistors R ₁ and R ₂ formed by 215 and 216, the potential V' of 220 becomes
V′=VR ₂ /(R ₁ +R ₂ ). Now, if we calculate the output potential V ₀ of 218, β of 213 and 214 is calculated.
Let β ₁ and β ₂ threshold voltages be V _THp2 and V _THo2 , becomes.

Therefore, if β ₁ =β ₂ and the resistance values R ₁ and R ₂ of 215 and 216 are made equal, V ₀ V _THp1 −V _THo1 /2+ V _THo2 −V _THp2 is obtained. Therefore, since V ₀ is given by the difference in the threshold voltages of the P-channel and N-channel field effect transistors, temperature can be detected using the temperature characteristics of the voltage difference. Further, V ₀ is a quantity that does not depend on the power supply voltage, and even if there is variation in threshold voltage between elements, the variation between elements can be eliminated because the difference is detected. or,
Since the voltage of V' is determined by the ratio of the resistance values of 215 and 216, it is possible to eliminate the effect of variations in resistance values when configured with an integrated circuit. In FIG. 2 of the embodiment according to the invention, 2
The potential of 20 will fluctuate due to the current flowing through 213 and 214 if the resistance values of 215 and 216 are not small enough, but the resistances of 215 and 216 can be made to a sufficiently small value by controlling the concentration during diffusion. Therefore, only the amount due to the difference in the threshold voltages of the elements appears as the potential of 218, and this variation due to temperature can be used as a means of temperature detection.

As described above, the present invention uses complementary field effect transistors to create a reference power supply that is independent of power supply voltage, and even if there is variation in resistance value during temperature detection, it can be removed. As mentioned above, the effect is extremely large when it is constructed on a semiconductor integrated circuit board.

FIG. 3 shows another embodiment of the present invention, in which field effect transistors 311 and 312 in FIG. 3 are added in order to further eliminate fluctuations with respect to the 220 power supply voltage.

In this example, since the conductance changes depending on the voltage applied to the gates of 311 and 312, the value of the difference in threshold values as described above can be obtained as the output of 218.

As mentioned above, the output potential V ₀ is expressed only by the difference in threshold voltage, so the temperature dependence dV ₀ /d _T
is expressed only by the difference in threshold voltage. Therefore, since temperature detection is possible only based on the difference in threshold voltage, it is independent of fluctuations in power supply voltage and variations in the process of integrated elements. Therefore, if this circuit is used to detect temperature based on the difference in threshold values, an extremely accurate temperature detection circuit can be realized.
The temperature detection circuit of the present invention can be applied not only to electronic watches but also to all circuits that require temperature control.

[Brief explanation of the drawing]

Figure 1 shows a conventional temperature detection circuit. FIGS. 2 and 3 show temperature detection circuits according to the present invention. 111 to 115 are resistors constructed on the semiconductor integrated circuit, 116 are transistors constructed on the semiconductor integrated circuit, 117 are outputs, 211 to 214 are field effect transistors constructed on the semiconductor integrated circuit, and 215 to 217 are transistors constructed on the semiconductor integrated circuit. A resistor configured on a semiconductor integrated circuit, 218 an output, 219 a bias potential point configured by a field effect transistor,
311 to 312 are field effect transistors constructed on a semiconductor integrated circuit.

Claims (1)

[Claims] 1a A first field effect transistor of a first conductivity type and a second field effect transistor of a second conductivity type connected in series between a first power supply and a second power supply. and b a third field effect transistor of the first conductivity type and a fourth field effect transistor of the second conductivity type connected in series between the first power source and the second power source; c a resistor connected between the first power source and the second power source to determine a bias potential of the third field effect transistor; d first drains of the first and second field effect transistors; a connection point is feedback connected to the gates of both the first and second field effect transistors, e the first drain connection point is input to the gate of the fourth field effect transistor, f the third and fourth field effect transistors; A temperature detection circuit characterized in that temperature detection is performed using an output of a second drain connection point of a field effect transistor.