JPS60202321A - Temperature detecting circuit - Google Patents

Abstract

PURPOSE:To obtain an accurate temperature data signal, whose digital processing is easy, by connecting a constant current power source and a capacitor in series between power sources, comparing the terminal voltage of the capacitor with a reference voltage, thereby omitting externally attached parts utilizing a small number of constituent elements. CONSTITUTION:When a discharge transistor Tr8 is turned OFF, positive electric charge is gradually injected into a capacitor 7 by a constant current transistor Tr6. A terminal voltage 11 is increased. When the voltage 11 becomes larger than a terminal voltage 12, the output of a voltage comparator 13 is inverted. The period up to the time, when the output 14 is inverted, is changed depending on the temperature. At a high temperature, the time period to the inversion is long. Conversely, at a low temperature, the time period to the inversion is short. Therefore, by measuring the time period, the temperature data in digital quantity can be readily obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a temperature detection circuit that is suitable for integration into an integrated circuit and can easily perform digital processing of temperature information.

[Prior art]

Various types of integrated temperature detection circuits have been announced so far. These are all temperature changes in the physical constants of a specific element, such as the pace of a bipolar transistor, the emitter voltage, etc.
It is common to process it as a digital signal using a converter or the like.

However, since the change due to the above-mentioned physical constant conversion is weak when used alone, a plurality of physical constants are usually used, and precise A/D g conversion is also required. Therefore, when integrated, it is necessary to adjust the constants in a subsequent process. For more precise A/Dm conversion, an increase in the pattern iMJ product and the need for external parts will also arise. [Purpose] The present invention is intended to eliminate the above-mentioned problems. The present invention provides a highly accurate temperature detection circuit that can obtain a temperature information signal that is easy to digitally process, does not require external components, and has high accuracy.

〔overview〕

The temperature/detection/sensing circuit of the present invention is characterized by having a small number of components, requiring no external parts, requiring few adjustment points, and being able to obtain a temperature information signal number with high precision and easy digital processing.

〔Example〕

The present invention will be described in detail below based on Examples. 1st
The figure shows an embodiment in which the present invention is implemented using complementary MO8 technology (hereinafter referred to as 0MO8).

In FIG. 1, P-channel transistors 1 and 3, N
Channel transistors 2 and 4, the above four transistor groups, generate a P-channel threshold voltage Vtp and an N-channel threshold voltage VtN, which are applied to the gates of P-channel transistor 6 and N-channel transistor 10, respectively. 6 and 10 are operated as constant current sources.

Constant current transistor 6 is connected in series between capacitor 7 and power supply. On the other hand, the constant current transistor 10 is connected in series between the two diodes 9 and the power supply. N-channel transistor 8 is a discharge switch that discharges capacitor 7. Further, the terminal voltage 12 of the diode 9 is applied to the 10 input of the voltage comparator 13, and the terminal voltage 11 of the capacitor 7 is applied to the - input. The circuit operation of the above configuration will be explained.

When the discharge transistor 8 is turned off when the current side 1=0, a positive charge is gradually injected into the 8-pin 7 by the constant current transistor 6, and the terminal voltage 11 gradually rises. Terminal voltage 1
1 becomes slightly greater than the terminal voltage 12, the output 14 of the voltage comparator 16 is inverted.

The time it takes for this output 14 to reverse varies significantly depending on the temperature. This will be explained using the following formula.

The constant current transistor 6 supplies P to the capacitor 7 from the constant current shown in equation (1).

From p = Z A 2 ・,・(1) β = μ0° 9 is used as a constant voltage source driven by a constant current transistor o.

Since the discharge transistor 8 is turned off at time 1=0, the terminal voltage V(τ) of the capacitor 7 at time t=τ is −1τ v(f)−−H, (op d, t−・(2 )C:
Since P is a constant current, V(τ) = Pτ (8). Now, in equation (1), COX, /L is unchanged with respect to temperature, and μ is expressed as TO=273°. Furthermore, the forward drop voltage VB per diode is VB (T) = VB (To) - & (T - To) - (5)
It is expressed as k龜2.5normal■, and remains almost constant with respect to minute changes in the bias current. Further, in the standard 0MO8 process, there is almost no variation in VB value.

From the above, the time τ until the input voltages 11 and 12 of the voltage comparator 16 become equal is expressed by the formula (3) I (4) I (
From 5) = Voa-2VB (T) = VDD-2VB (To) + 2 & (T-To)...
(6) V o o: % source voltage (7). From equation (7), it can be seen that as the temperature T increases, τ becomes longer. This situation is illustrated in Figure 2. In Figure 2, at high temperatures, 2vB202 is small and r is also smaller than the constant current, so the capacitor terminal voltage 203
The rise of <2VB is slow, and it takes a long time to cross 2VB 202, so it takes a long time to invert the output 204 of the voltage comparator. On the other hand, at low temperatures, the terminal voltage 206 of the capacitor rises quickly and 2VB205 is also large, so the time until the output 207 of the voltage comparator is inverted is short.

FIG. 6 shows the forward drop voltage VB50 of the diode.
1 and constant current shows the temperature characteristics of P2O3. FIG. 4 shows the temperature characteristics at time τ401 expressed by equation (γ).

As mentioned above, the time τ is the temperature T to the 5/2 power and 3/2
Since it changes by the power of τ, the length of τ indicates the height of the temperature. Therefore, by measuring the time τ, it is possible to easily obtain digital temperature information.

In this embodiment, the reference voltage VB has temperature characteristics, but temperature detection is also possible using a reference voltage that does not have temperature characteristics. In this case, the time τ changes as the temperature T to the 372nd power, and the accuracy decreases. Now, in the example shown in Figure 1, In? ==I O”A, O=10py, τ
~10-2 seconds, and in order to know the temperature change of about 0.1℃, the counting frequency for counting τ is several hundred K.
Hz or higher is required.

There is no problem if the system clock frequency is several hundred KH2 or more, but with a 32KHz original frequency like a clock IC,
A problem arises in terms of accuracy. As a countermeasure, it is possible to further reduce op or to increase the capacitance 0, but making r even smaller than 10→A is important in terms of leakage on the integrated circuit and in adjusting the current value. However, increasing the capacitance C increases the pattern area and cannot be adopted.

A second embodiment for avoiding the above problems is shown in FIG.

In FIG. 5, respective threshold voltages are applied to constant current transistors 6 and 10 from a bias generating circuit 501. In FIG. The difference from the first embodiment is that the output 14 of the voltage comparator 13 is passed through the inverter 21 to the discharge transistor 8.
is applied to the gate of

Now, when the output 14 of the voltage comparator 16 is LOW, the discharge transistor 8 is turned on and the capacitor 7 is discharged.

Then, the output 14 becomes Hlgh, and the discharge transistor 8
is turned off, and the capacitor 7 is gradually charged by the constant current transistor 6, and when the voltage reaches the same voltage as the terminal voltage 12, the output 14 is inverted and the capacitor 7 is discharged. By repeating the above operation, repeated pulses are obtained at the output 14. By counting these repeated pulses, temperature information can be obtained. The frequency f of the repetitive pulse of the output 14 is f='/ from equation (7).

, and f is proportional to the temperature T to the -72nd power and the 13/2th power. Therefore, as shown in FIG.
The frequency f of 1 is small, and the frequency f of the repetitive pulse 602 becomes large at low temperatures.

The above was explained using an example in which the present invention was implemented in CMOS.
As shown in FIG. 7, even if both the P-channel and N-channel transistors are replaced, a 4:4 configuration is possible. Furthermore, the reference voltage source is not limited to a diode; for example, a difference in threshold voltage may be used, or a constant voltage source with or without temperature characteristics may be used.

〔effect〕

As described above, according to the present invention, with a small pattern area,
Digital processing allows you to obtain high-capacity temperature ↑a information.

The above digital processing can be used to measure the time until the output of the voltage comparator is reversed or to measure the repetition frequency of the output of the voltage comparator, so there is a degree of freedom in actual use. The scope of application is wide. Further, although it is necessary to adjust the constant current value, it is not particularly difficult because it can be done by selecting the size of the constant current transistor.

[Brief explanation of the drawing]

Fig. 1 shows the first embodiment of the present invention. Fig. 5...
・Bias generation circuit 16...bias 17 of transistor 6...bias 15 of transistor 10...electrode of discharge transistor 8 FIG. 2 (α), Cb) is an operation timing diagram of the circuit in FIG. 1 ・201 ...The gate potential of the discharge transistor Fig. 6 shows the temperature characteristics of constant current and constant voltage. Fig. 4 shows the warm characteristics of the time until the voltage comparator is reversed. Fig. 5 shows the temperature characteristics of the second embodiment of the present invention. Diagram 501 showing an example...
Bias generation circuit Fig. 6 (a), (i is the operation timing diagram of @Ayu in Fig. 5) Fig. 7 is a diagram 701 showing the third embodiment of the present invention...
Bias generation circuit 702... Capacitor 705... Discharge transistor 704... Constant current transistor 705... Constant current transistor 706... Diode group 707... Voltage comparator 708... Capacitor terminal voltage 709 ...Diode group terminal voltage 710--Discharge transistor electrode □711...More than voltage comparator output Applicant Suwa Seikosha Co., Ltd. Agent Patent attorney Tsutomu Mogami Figure 1 Figure 2 Figure 3 Figure 1 Degree 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] (Li) A constant current source and a capacitor are connected in series between power supplies, and a current source with a constant current source of t'+tJ is provided, comprising a comparator that compares a terminal voltage of the capacitor with a reference voltage. is a temperature detection circuit characterized in that its redundant current value changes with temperature. (2) Claim 1 characterized in that the voltage value of reference '1t1.pressure changes with temperature. The temperature detection circuit according to claim 1. (3) The temperature detection circuit according to claim 1, characterized in that the discharge switch opens and closes depending on the comparison result.