JPH06258145A - Temperature monitor circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To suppress the change of the temperature identification point of the temperature monitor circuit due to the process variation and stabilize the operation of the automatic power-off mechanism including the temperature monitor circuit. [Structure] A first constant current source composed of a transistor T ₁ and a resistor R _2, which forms a predetermined reference potential V _R by flowing a current I ₁ through the resistor R ₁ , and a transistor T ₂ and a resistor R _3.
Second , which forms the temperature monitor potential V _D by flowing the current I ₂ through the diodes D _{1 to} D ₃ which are composed of
Of a constant current source, the temperature monitor circuit including a differential amplifier circuit DA for receiving a reference potential V _R and the temperature monitor potential V _D, providing a current feedback path comprising a resistor R ₄ and R _5. As a result, the gradient of the amount of change in the temperature monitor potential V _D due to the change in the saturation current of the diode is made gentle, and the difference between the reference potential V _R and the temperature monitor potential V _D , that is, the amount of change in the potential of the temperature monitor circuit as a whole. On the other hand, it is possible to suppress the change in the temperature identification point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature monitor circuit, and more particularly to a technique which is particularly effective when used in a temperature monitor circuit included in an automatic power-off mechanism of a computer system.

[0002]

2. Description of the Related Art The forward temperature or the base-emitter voltage of a diode or a transistor (in this specification, a bipolar transistor is simply referred to as a transistor) is changed according to its junction temperature to control the temperature inside the device. There is a temperature monitor circuit to monitor. In addition, there is an automatic power-off mechanism that includes a temperature monitoring circuit and automatically turns off the power by identifying that the temperature inside the device has abnormally increased due to a failure of the cooling device, etc. is there.

Regarding a computer system having an automatic power-off mechanism and its integrated operation management, for example, 1
In 991, "HITAC M" issued by Hitachi, Ltd.
880 Processor Group Catalog ", page 15, etc.

[0004]

Prior to the present invention, the inventors of the present application implemented a temperature monitor circuit as shown in FIG. 5 as a temperature monitor circuit used in the automatic power-off mechanism of the computer system described above. developed. In the figure, the temperature monitor circuit has a base with a predetermined constant voltage V.
_It receives _CS and its emitter is supplied with a power supply voltage V _EE via a resistor R _2.
Similarly, the transistor T ₁ acting as a constant current source by being coupled to the constant current source and the base of which receives the constant voltage V _CS and the emitter of which is coupled to the power source voltage V _EE via the resistor R ₃ are also the constant current source. And a transistor T ₂ acting as. The constant current source composed of the transistor T ₁ and the resistor R ₂ supplies a predetermined current I ₁ to the resistor R ₁ to form a predetermined reference potential V _R. Also, the transistor T ₂ and the resistor R ₃
The constant current source consisting of 3 supplies a predetermined current I ₂ to the _three diodes D _{1 to} D ₃ in series to form the temperature monitor potential V _D. The reference potential V _R is supplied to the inverting input terminal − of the differential amplifier circuit DA, and the temperature monitor potential V _D is supplied to its non-inverting input terminal +.

Here, the reference potential V _R is obtained as V _R = V _CC -I ₁ R ₁ . In addition, the current I ₁ is applied to the transistor T ₁
When the base-emitter voltage of V _BE1 is V _BE1 , I ₁ = (Vcs−V _BE1 −V _EE ) / R ₂ is satisfied. Therefore, the reference potential V _R is

[Number 1] V _R = V _CC - the _{(R 1 / R 2) (} Vcs-V BE1 -V EE).

On the other hand, the temperature monitor potential V _D is obtained as V _D = V _CC -3V _F when the forward voltage of the diodes D _{1 to} D ₃ is V _F. Further, as is well known, the forward voltage V _F of the diodes D _{1 to} D ₃ is V _F = (kT / q) (lnI ₂ −lnI _S ) when its saturation current is I _S , and this formula Forward current I ₂ of transistor T
_When the base-emitter voltage of ₂ is V _BE2 , I ₂ = (Vcs−V _BE2 −V _EE ) / R ₃ is obtained. Therefore, the temperature monitor potential V _D is

## EQU00002 ## V _D = V _CC -3 (kT / q) [ln {(Vcs-V _BE2- V _EE ) / R ₃ } -lnI _S ]. In the above equation, k is a Boltzmann's constant, q is an electron charge amount, and T is a junction temperature of the diodes D _{1 to} D _{3 in} absolute temperature display, that is, a computer system including this temperature monitor circuit. It corresponds to the temperature inside the device. I _S is the saturation current of the diodes D _{1 to} D ₃ , and lnI ₂ and lnI _S represent the natural logarithms of the forward current I ₂ and the saturation current I _S of the diodes D _{1 to} D ₃ , respectively. Hereinafter, similarly, the natural logarithmic value is denoted by ln.

In Equations 1 and 2, when the potential of each power supply voltage and the current values of the currents I ₁ and I ₂ can be regarded as constant, the ground potential V _CC , the constant voltage V _CS , the power supply voltage V _EE, and the transistor T _{1 Has} a constant base-emitter voltage V _BE1 . Therefore, as shown in FIG. 4, the reference potential V _R is a constant potential that is not changed by the internal temperature T of the apparatus, and the potential of the temperature monitor potential V _D is the currents I ₂ and I _{2.
Since S} has a substantially constant value smaller than 1, it increases in proportion to the temperature T in the apparatus. The output signal TMO of the differential amplifier circuit DA is a low level when the device temperature T is the differential amplifier circuit DA that is, the temperature monitor potential V _D lower than the temperature identification point PA of the temperature monitor circuit is lower than the reference potential V _R Then, the temperature T inside the device is determined by the temperature identification point PA of the temperature monitor circuit.
When the temperature monitor potential V _D becomes higher than the reference potential V _R and exceeds the reference potential V _R , it is inverted to a high level. That is, in the temperature monitor circuit of FIG. 5, it is possible to identify that the temperature inside the apparatus has become abnormally high due to the high level change of the output signal TMO of the differential amplifier circuit DA, and automatically turn off the power of the computer system. Becomes

However, as the performance of computer systems has advanced, it has become clear by the inventors of the present application that the above-mentioned temperature monitor circuit also has the following problems. That is, in Equation 2, the saturation current I _S of the diodes D _{1 to} D ₃ is considered to be a substantially constant value. However, as is well known, I _S = q {(D _p p _no ) / L _p + (D _n n _po ) / L _n }, resulting in process variations, that is, the diffusion constant D _p and diffusion length L _{p of the} P-type impurity and the diffusion constant D of the N-type impurity.
_{It is} a function of _n and the diffusion length L _n . Further, as is clear from the equation 1, the reference potential V _R is as shown in FIG.
While being a constant value that does not cause potential variation [Delta] V _R by the natural logarithm lnI _S saturation current I _S, the temperature monitor potential V _D from Equation 2,

## EQU00003 ## V _D = V _CC -3 (kT / q) ln {(Vcs-V _BE2- V _EE ) / R ₃ } +3 (kT / q) lnI _S , which is the natural logarithmic value of the saturation current I _S. A potential change amount ΔV _D proportional to lnI _S is generated. Note that p _no in the above equation is the minority carrier density of the P-type semiconductor in the thermal equilibrium state,
n _po is the minority carrier density of the N-type semiconductor.

Considering the variation of the temperature monitor circuit as a model, as is apparent from FIG. 4, when the temperature monitor potential V _D is constant, the rise of the reference potential V _R , that is, the potential change amount + ΔV _R, is the temperature monitor circuit. Temperature discrimination point is increased to the operating point PB side, and its decrease, that is, the amount of potential change −
ΔV _R lowers this to the operating point PC side. On the other hand, if the reference potential V _R is constant, the rise of the temperature monitor potential V _D , that is, the amount of potential change + ΔV _D , on the contrary, lowers the temperature identification point of the temperature monitor circuit to the operating point PD side, and the decrease, that is, the amount of potential change. -ΔV _D raises this to the operating point PE side. In other words, the change in temperature identification points viewed as a whole the temperature monitor circuit, the reference potential V difference clogging [Delta] V between the potential variation [Delta] V _D of the potential variation [Delta] V _R and the temperature monitor potential V _D of _{R R} - [Delta] V _D
Although becomes proportional to, the conventional temperature monitoring circuits, the difference [Delta] V _R - [Delta] V _D, as shown in FIG. 6, the temperature monitor potential V _D in the axial natural logarithm lnI _S saturation current The potential change amount ΔV _D is mirror-inverted, and increases in the negative direction as the natural logarithm lnI _S of the saturation current increases. As a result, the temperature discrimination point of the temperature monitor circuit changes due to the saturation current I _S of the diodes D _{1 to} D ₃ , that is, the process variation, which limits the performance improvement of the computer system including the temperature monitor circuit. .

An object of the present invention is to provide a temperature monitor circuit which suppresses changes in temperature identification points due to process variations. Another object of the present invention is to stabilize the operation of an automatic power-off mechanism including a temperature monitor circuit, and to promote high performance of a computer system including an automatic power-off mechanism.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0012]

The outline of the representative one of the inventions disclosed in the present application will be briefly described as follows. That is, a first transistor that receives a predetermined constant voltage at its base and a second resistance means, one of which is coupled to the emitter of the first transistor, is used to cause a predetermined current to flow through the first resistance means. A first constant current source for forming a predetermined reference potential; a second transistor for receiving the constant voltage at its base; and a third resistance means, one of which is coupled to the emitter of the second transistor. A second constant current source that forms a temperature monitor potential by causing a predetermined current to flow through a diode serving as a detection element, and one of its input terminals receives the reference potential and the other input terminal receives the temperature monitor potential. A temperature monitor circuit including a differential amplifier circuit; and a fourth resistance means provided between the other of the first and second resistance means connected in common and a second power supply voltage; Add current feedback path including a fifth resistor means provided between the base sheet point and the second transistor.

[0013]

According to the above means, while suppressing the potential change of the reference potential of the temperature monitor circuit due to the change of the saturation current of the diode serving as the temperature detecting element, the slope of the amount of change in the potential of the temperature monitor potential is made gentle and the reference potential is reduced. Also, the difference in the potential change amount of the temperature monitor potential, that is, the slope of the potential change amount seen in the temperature monitor circuit as a whole can be made gentle.
As a result, changes in the saturation current of the diode, that is, changes in the temperature identification point of the temperature monitor circuit due to process variations, can be suppressed, so the operation of the automatic power-off mechanism including the temperature monitor circuit is stabilized, and automatic power-off is performed. It is possible to promote higher performance of a computer system including the mechanism.

[0014]

1 is a circuit diagram of an embodiment of a temperature monitor circuit to which the present invention is applied. Further, FIG. 3 shows a characteristic diagram of an embodiment showing the relationship between the reference potential and the temperature monitor potential in the temperature monitor circuit of FIG. 1 and the natural logarithm of the saturation current of the diode, and FIG. The characteristic view of one embodiment showing the relationship between the temperature discrimination point of the temperature monitor circuit of No. 1 and the temperature inside the apparatus is shown. Based on these figures, the configuration and operation of the temperature monitor circuit of this embodiment and its features will be described. The temperature monitor circuit of this embodiment is included in the automatic power-off mechanism of the computer system, although not particularly limited. Each circuit element of FIG. 1 is formed on one semiconductor substrate such as single crystal silicon together with other predetermined circuit elements (not shown) of the automatic power-off mechanism. In the following circuit diagrams, the bipolar transistors shown are all NPN type transistors.

In FIG. 1, the temperature monitor circuit of this embodiment includes a transistor T ₁ (first transistor) which receives a predetermined constant voltage V _CS at its base. The collector of the transistor T ₁ is coupled to the ground potential V _CC (first power supply voltage) via the resistor R ₁ (first resistance means), and its emitter is connected to the resistor R ₂ (second resistance means). Combined with one. As a result, the transistor T ₁ constitutes a constant current source (first constant current source) together with the resistor R ₂ , and a predetermined current I ₁ is passed through the resistor R ₁ to form a predetermined reference potential V _R. The collector potential of the transistor T ₁ , that is, the reference potential V
_R is supplied to one input terminal of the differential amplifier circuit DA, that is, the inverting input terminal −.

The temperature monitoring circuit further comprises another transistor T ₂ (second node) whose base is coupled to the supply point of the constant voltage V _CS via a resistor R ₅ (fifth resistor means).
Transistor). The collector of the transistor T ₂ is not particularly limited, but is connected to the ground potential V via _three diodes D _{1 to} D ₃ (temperature detecting elements) in series.
_It is coupled to _CC and its emitter is coupled to one of the resistors R ₃ (third resistance means). As a result, the transistor T ₂ becomes constant current source (second constant current source) together with the resistor R _3.
And a predetermined current I ₂ is passed through the diodes D _{1 to} D ₃ to form the temperature monitor potential V _D. Transistor T
The collector potential of ₂ , that is, the temperature monitor potential V _D is supplied to the other input terminal of the differential amplifier circuit DA, that is, the non-inverting input terminal +. The other of the resistors R ₂ and R ₃ is coupled to the power supply voltage V _EE (second power supply voltage) via the resistor R ₄ (fourth resistance means) forming the current feedback path.

Consequently, the output signal TMO of the differential amplifier circuit DA, that is, the temperature monitor circuit is set to a predetermined low level when the temperature monitor potential V _D is lower than the reference potential V _R , and the temperature monitor potential V _D is the reference potential V _R. When it is higher, it is set to a high level like the ground potential V _CC . When the output signal TMO of the temperature monitor circuit is set to a high level, a predetermined power supply disconnection circuit is activated in the automatic power supply disconnection mechanism including the temperature monitor circuit, whereby the power supply of the computer system is automatically disconnected. .

In this embodiment, the reference potential V _R obtained as the collector potential of the transistor T ₁ of the temperature monitor circuit is

## EQU4 ## V _R = V _CC -I ₁ R ₁ is obtained. Further, the temperature monitor potential V _D obtained as the collector potential of the transistor T ₂ is obtained as V _D = V _CC −3V _F when the forward voltage of the diodes D _{1 to} D ₃ is V _F, and the diode D ₁ is obtained. ~ D ₃ forward voltage V
_{Since F} is V _F = (kT / q) (lnI ₂ −lnI _S ),

## EQU5 ## V _D = V _CC -3 (kT / q) (lnI ₂ -lnI _S ).

Current values of the currents I ₁ and I ₂ obtained by the two constant current sources including the transistors T ₁ and T ₂ with the ground potential V _CC and the power supply voltage V _EE and the potential of the constant current source V _CS regarded as constant. when it can be considered a constant, reference voltage V _R
4 has a constant potential that is not changed by the temperature T in the apparatus, and the potential of the temperature monitor potential V _D has a substantially constant value in which the currents I ₂ and I _S are smaller than 1. , Increases in proportion to the temperature T in the apparatus. Therefore, the output signal TMO of the differential amplifier circuit DA, that the temperature monitoring circuit is less than the differential amplifier circuit DA clogging Temperature Temperature monitoring lower than the temperature discrimination point PA of the monitor circuit potential V _D is the reference potential V _R device temperature T At this time, it is set to the low level, and when the temperature T in the apparatus exceeds the temperature identification point PA of the temperature monitor circuit and the temperature monitor potential V _D becomes higher than the reference potential V _R , it is inverted to the high level. In the automatic power-off mechanism including the temperature monitor circuit, a predetermined power-off circuit differentially operates in response to a change in the output signal TMO of the differential amplifier circuit DA to a high level, whereby the power of the computer system is automatically turned off. .

By the way, the transistor T ₁ and the resistor R ₂
In the constant current source consisting of, when the base-emitter voltage of the transistor T ₁ is V _BE1 , the following relationship holds: V _EE = V _CS −V _BE1 −I ₁ R ₂ − (I ₁ + I ₂ ) R ₄ The current I ₁ is

## _EQU6 ## I ₁ = (V _CS −V _BE1 −I ₂ R ₄ −V _EE ) / (R ₂ + R ₄ ). On the other hand, in the constant current source composed of the transistor T ₂ and the resistor R ₃ , assuming that the base-emitter voltage of the transistor T ₂ is V _BE2 and the resistance value of the resistor R ₅ is zero, V _EE = V _CS −V _BE2 − Since the relationship of I ₂ R ₃ − (I ₁ + I ₂ ) R ₄ is established, the current I ₂ is

## _EQU7 ## I ₂ = (V _CS −V _BE2 −I ₁ R ₄ −V _EE ) / (R ₃ + R ₄ ).

Therefore, by substituting equation 7 into equation 6,

I ₁ = {R ₃ (V _CS −V _EE ) − (R ₃ + R ₄ ) V _BE1 + R ₄ V _BE2 } / {(R ₂ + R ₄ ) (R ₃ + R ₄ ) −R ₄ ² } Is obtained, and on the contrary, Substituting Equation 6 into Equation 7,

Equation 9] _{I 2 = {R 2 (V} CS -V EE) + R 4 V BE1 - (R 2 + R 4) V BE2} / {(R 3 + R 4) (R 2 + R 4) -R 4 2} Is obtained.

From these facts, the above-mentioned formula 4 becomes the formula 8
Substituting

## EQU10 ## V _R = V _CC −R ₁ {R ₃ (V _CS −V _EE ) − (R ₃ + R ₄ ) V _BE1 + R ₄ V _BE2 } / {(R ₂ + R ₄ ) (R ₃ + R ₄ ) -R ₄ ² }, and the above Equation 5 is substituted by Equation 9,

Equation 11] _{V D = V CC -3 (kT} / q) ln [{R 2 (V CS -V EE) + R 4 V BE1 - (R 2 + R 4) V BE2} / {(R 3 + R 4) (R ₂ + R ₄ ) −R ₄ ² }] +3 (kT / q) lnI _S.

Here, if the constant current characteristic of the circuit is guaranteed, the base-emitter voltages V _BE1 and V _BE2 of the transistors T ₁ and T ₂ are V _BE1 = V _BE2 = V _BE and V _BE = Since (kT / q) (lnI ₁ −lnI _s ) = (kT / q) (lnI ₂ −lnI _s ), the above formula 10 is

## EQU12 ## V _R = V _CC -R ₁ {R ₃ (V _CS -V _EE ) -R ₃ V _BE } / {(R ₂ + R ₄ ) (R ₃ + R ₄ ) -R ₄ ² } = V _CC -R ₁ {R ₃ (V _CS −V _EE ) − R ₃ (kT / q) (lnI ₁ −lnI _S )} / {(R ₂ + R ₄ ) (R ₃ + R ₄ ) −R ₄ ² } . As a result, the reference potential V _R has a saturation current I _{S with a} proportional coefficient K _{A of} K _A = R ₁ R ₃ (kT / q) / {(R ₂ + R ₄ ) (R ₃ + R ₄ ) −R ₄ ² }. Natural logarithm of l
It is inversely proportional to nI _S. However, in this embodiment, the resistance values of the resistors R _{1 to} R ₄ are set so that the proportionality coefficient K _A becomes so small that it can be ignored.
_As shown in FIG. 3, the potential change amount ΔV _R of _R is the natural logarithmic value lnI _S of the saturation current I _S of the diodes D _{1 to} D _3.
As becomes larger, it increases slightly in the negative direction.

On the other hand, when the constant current characteristic of the circuit is guaranteed,
The above formula 11 is

V _D = V _CC -3 (kT / q) ln [{R ₂ (V _CS -V _EE ) -R ₂ V _BE } / {(R ₃ + R ₄ ) (R ₂ + R ₄ ) -R ^{_{4 2}] + 3 (kT}} / q) lnI S = V CC -3 (kT / q) ln [{R 2 (V CS -V EE) - R 2 (kT / q) (lnI 2 -lnI S)} _{/ {(R 3 + R 4} ) (R 2 + R 4) -R 4 2}] + 3 (kT / q) lnI S = V CC -3 (kT / q) ln (K B + K C lnI S) + 3 ( kT / q) lnI _S. Here, K _B in the above equation is K _B = R ₂ {V _CS −V _EE − (kT / q) lnI ₂ } / {(R ₃ + R ₄ ) (R ₂ + R ₄ ) −R ₄ ² }. K _C is a constant and is a proportional coefficient of the natural logarithmic value lnI _{S such} that K _C = R ₂ (kT / q) / {(R ₃ + R ₄ ) (R ₂ + R ₄ ) −R ₄ ² }.

As is clear from the comparison between this equation 13 and the above equation 3, the first term and the third term of equation 13 are
That is, that is, the potential change amount ΔV _D of the conventional temperature monitor potential V _D shown by the dotted line in FIG. Further, the second term of the mathematical expression 13 is the potential change amount Δ of the temperature monitor potential V _D.
It acts to reduce V _D , and its value is the reference potential V
It is designed to be sufficiently large compared to the potential variation [Delta] V _R of _R. Therefore, the potential change amount ΔV of the temperature monitor potential V _D in the temperature monitor circuit of this embodiment.
_D is the natural logarithm lnI _S takes a relatively small value portion of the saturation current I _S, the potential variation of the conventional temperature monitor potential V _D shown by a dotted line is reduced by the action of the second term of Equation 13 While gradually away from a straight line [Delta] V _D, the saturation current after the natural logarithm lnI _S of I _S is a relatively large value, the linear potential variation [Delta] V _D of the conventional temperature monitor potential V _D shown by a dotted line Grows along. As a result, the slope of the potential variation [Delta] V _D of the temperature monitor potential V _D becomes what is small in the natural logarithm lnI _S takes a relatively small value portion of the saturation current I _S.

As shown in FIG. 4, the temperature monitor potential V
When a constant _D, increases i.e. the potential variation of the reference potential V _R + [Delta] V _R, the differential amplifier circuit DA, that the temperature discrimination point of the temperature monitor circuit is increased to the operating point PB side, the decrease i.e. potential change amount -ΔV _R lowers this to the operating point PC side. On the other hand, if the reference potential V _R is kept constant, the rise of the temperature monitor potential V _D , that is, the amount of potential change + ΔV _D , on the contrary, lowers the temperature identification point of the temperature monitor circuit to the operating point PD side, and the decrease, that is, the potential change. The amount −ΔV _D makes this higher on the operating point PE side. Thus, changes in temperature identification points viewed as a whole the temperature monitor circuit, reference potential V potential variation of the _R [Delta] V _R
And the difference between the temperature monitor potential V _{D and} the potential change amount ΔV _D , that is, ΔV _R −ΔV _D. In this embodiment, the difference [Delta] V _R - [Delta] V between the reference potential V potential variation of the _R [Delta] V _R and the temperature monitor potential V _D of the potential variation [Delta] V _D
D, as shown in FIG. 3, in the portion where the natural logarithm lnI _S saturation current I _S takes a relatively small value, decreases in the potential variation [Delta] V _D of the temperature monitor potential V _D is small, the dotted line in it away from the conventional differential [Delta] V _R - [Delta] V _D shown after natural logarithm lnI _S saturation current I _S is a relatively large value, the conventional differential [Delta] V _R represented by a dotted line -
It increases with the same inclination as ΔV _D. Therefore, the difference ΔV _R
Slope of - [Delta] V _D is a natural logarithm lnI _S saturation current I _S
Becomes smooth in the portion where takes a relatively small value, and its size is an average small value. As a result, a change in the saturation current I _S of the diode, that is, a change in the temperature identification point of the temperature monitor circuit due to process variation can be suppressed, so that the operation of the automatic power-off mechanism including the temperature monitor circuit is stabilized, and the automatic power-off mechanism is activated. It is possible to promote high performance of the computer system including it.

By the way, in the above description, it is assumed that the constant current characteristic of the circuit is guaranteed, and the base-emitter voltages V _BE1 and V _BE2 of the transistors T ₁ and T ₂ are V _BE1 = V _BE2 = V _BE . It has been assumed that there is a relationship, but in reality the currents I ₁ and I ₂ obtained by the constant current source change, and with these current changes the base-emitter voltages V _BE1 and V ₂ of the transistors T ₁ and T ₂ V _BE2 changes.

[0028] Here, the base-emitter voltage V of the current I ₁ and the transistors T ₁ obtained by transistors T _1
BE1 is assumed to be constant with respect to current I ₂ current I ₁ provided by transistor T _2, I ₂ = I ₁ + [Delta] I made changes with a difference [Delta] it, the base-emitter voltage V _BE2 of the transistor T ₂ is the transistor If the base emitter voltage V _BE1 of T ₁ is changed with a difference ΔV _{BE of} V _BE2 = V _BE1 + ΔV _BE , the formula 10 is

V _R = V _CC −R ₁ {R ₃ (V _CS −V _EE ) − (R ₃ + R ₄ ) V _BE1 + R ₄ (V _BE1 + ΔV _BE )} / {(R ₂ + R ₄ ) ( R ₃ + R ₄ ) −R ₄ ² } = V _CC −R ₁ {R ₃ (V _CS −V _EE ) −R ₃ V _BE1 + R ₄ ΔV _BE )} / {(R ₂ + R ₄ ) (R ₃ + R ₄ ) -R ₄ ² }, and Equation 11 is

[Equation 15] V _D = V _CC -3 (kT / q) ln [{R ₂ (V _CS -V _EE ) + R ₄ V _{BE 1-} (R ₂ + R ₄ ) (V _{BE 1} + ΔV _BE )} / {(R _{3 + R 4) (R 2} + R 4) -R 4 2}] + 3 (kT / q) lnI S = V CC -3 (kT / q) ln [{R 2 (V CS -V EE) - R 2 V _BE1 - a _{(R 2 + R 4) ΔV} bE)} / {(R 3 + R 4) (R 2 + R 4) -R 4 2}] + 3 (kT / q) lnI S.

On the other hand, the base-emitter voltages V _BE1 and V _BE2 of the transistors T ₁ and T ₂ are as follows: V _BE1 = (kT / q) (lnI ₁ −lnI _S ) V _BE2 = (kT / q) (lnI ₂ −lnI obtained as _S), also assuming a V _BE2 = V _BE1 + ΔV _bE the relationship, the difference [Delta] V _bE with respect to the base-emitter voltage V _BE1 of the transistor T ₁ of the base-emitter voltage V _BE2 of the transistor T ₂ are, [Delta] V _bE = V _{BE2 -V BE1 = (kT / q} ) (lnI 2 -lnI S) - and comprising _{(kT / q) (lnI 1} -lnI S) = (kT / q) (lnI 2 -lnI 1).

Therefore, the above equation 14 is

V _R = V _CC −R ₁ {R ₃ (V _CS −V _EE ) −R ₃ (kT / q) (lnI ₁ −lnI _S ) + R ₄ (kT / q) (lnI ₂ −lnI ₁ )} / {(R ₂ + R ₄ ) (R ₃ + R ₄ ) −R ₄ ² } = V _CC −R ₁ {R ₃ (V _CS −V _EE ) − (R ₃ + R ₄ ) (kT / q) lnI ₁ + R ₄ (kT / q) lnI ₂ −R ₃ (kT / q) lnI _S } / {(R ₂ + R ₄ ) (R ₃ + R ₄ ) −R ₄ ² }

Equation 17] _{V D = V CC -3 (kT} / q) ln [{R 2 (V CS -V EE) - R 2 (kT / q) (lnI 1 -lnI S) - (R 2 + R 4) (KT / q) (lnI ₂ −lnI ₁ )} / {(R ₃ + R ₄ ) (R ₂ + R ₄ ) −R ₄ ² }] + 3 (kT / q) lnI _S = V _CC -3 (kT / q ) Ln [R ₂ {V _CS −V _EE + (R ₄ / R ₂ ) (kT / q) lnI ₁ } − (R ₂ + R ₄ ) (kT / q) lnI ₂ + R ₂ (kT / q) lnI _S } / {(R ₃ + R ₄ ) (R ₂ + R ₄ ) −R ₄ ² }] + 3 (kT / q) lnI _S.

As previously mentioned, the current I ₁ is considered constant and the current I ₂ is I ₂ = I ₁ + ΔI. Therefore, the reference potential V _R of the equation 16 has a proportional coefficient K _D of K _D = R ₁ R ₄ (kT / q) / {(R ₂ + R ₄ ) (R ₃ + R ₄ ) −R ₄ ² } ₂ That is, current I ₁ +
Proportional to the natural logarithmic value ln (I ₁ + ΔI) of ΔI, and K _E = R ₁ R ₃ (kT / q) / {(R ₂ + R ₄ ) (R ₃ + R ₄ ) −R ₄ ² } The coefficient K _E is proportional to the natural logarithm lnI _S of the saturation current I _S of the diodes D _{1 to} D ₃ . The temperature monitor potential V _D of the formula _{17, K F = R 2 {V} CS -V EE + (R 4 / R 2) (kT / q) lnI 1} / {(R 3 + R 4) (R 2 ^{_{+ R 4) -R 4 2}}} K G = (R 2 + R 4) (kT / q) / {(R 3 + R 4) (R 2 + R 4) -R 4 2} K H = R 2 (kT / q ) / {(R ₃ + R ₄ ) (R ₂ + R ₄ ) −R ₄ ² },

V _D = V _CC −3 (kT / q) ln {K _F −K _G lnI ₂ + K _H lnI _S } = V _CC −3 (kT / q) ln {K _F −K _G ln (I ₁ + ΔI) + K _H lnI _S }.

As can be inferred by engineers engaged in related fields, the difference ΔI between the current I _{2 and} the current I ₁ is
This can be intentionally obtained by the feedback resistor R ₅ provided between the base of the transistor T ₁ of FIG. 1, that is, the supply point of the constant voltage V _CS and the base of the transistor T ₂ . Also,
As is clear from the comparison between the equation 18 and the equation 13, the term K _G ln (I ₁ + ΔI) in the equation 18 is the current I ₂
Of the temperature monitor potential at a portion where the natural logarithmic value lnI _S of the saturation current I _S in FIG. 3 has a relatively small value. The slope of V _D becomes even gentler. As a result, by providing the feedback resistor R _S , the reference potential V due to the process variation is obtained.
The difference between _R and the temperature monitor potential V _D ΔV _R −ΔV _D, that is, the change in the temperature discriminating point of the temperature monitor circuit as a whole is further reduced, and the operation of the automatic power-off mechanism including the temperature monitor circuit is accordingly stabilized. Will be things.

As shown in the above-described embodiment, by applying the present invention to the temperature monitor circuit included in the automatic power-off mechanism of the computer system, the following operational effects can be obtained. That is, (1) a first transistor which receives a predetermined constant voltage at its base and a second resistance means, one of which is coupled to the emitter of the first transistor, is provided with a predetermined current to the first resistance means. A first constant current source which forms a predetermined reference potential by flowing the second constant current source, a second transistor which receives the constant voltage at its base, and a third resistance means, one of which is coupled to the emitter of the second transistor. And a second constant current source for forming a temperature monitor potential by causing a predetermined current to flow in a diode serving as a temperature detecting element, and one of the input terminals receives the reference potential and the other input terminal receives the temperature monitor. A temperature monitor circuit having a differential amplifier circuit for receiving a potential; and a fourth resistance means provided between the second commonly connected first and second resistance means and the second power supply voltage; Electric By adding a current feedback path including a fifth resistance means provided between the voltage supply point and the base of the second transistor, the potential of the reference potential of the temperature monitor circuit according to the change of the saturation current of the diode is added. The effect that the slope of the amount of change in the potential of the temperature monitor potential can be made gentle while suppressing the change is obtained.

(2) According to the above item (1), the difference between the potential change amount of the reference potential and the potential change amount of the temperature monitor potential, that is, the slope of the potential change amount viewed from the entire temperature monitor circuit can be made gentle. The effect is obtained. (3) According to the above items (1) and (2), it is possible to suppress the change in the saturation current of the diode, that is, the change in the temperature identification point of the temperature monitor circuit due to the process variation. (4) According to the above items (1) to (3), it is possible to stabilize the operation of the automatic power-off mechanism including the temperature monitor circuit and promote the high performance of the computer system including the automatic power-off mechanism. The effect is obtained.

Although the invention made by the present inventor has been specifically described based on the embodiments, the invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say. For example, in FIG. 1, the number of diodes provided as the temperature detection element can be set arbitrarily, and a bipolar transistor or the like can be used as the temperature detection element. The reference potential V _R and the temperature monitor potential V _D are the differential amplifier circuit DA.
May be input to the opposite input terminals, that is, the non-inverting and inverting input terminals, respectively. In this case, it goes without saying that the logic level of the output signal TMO of the differential amplifier circuit DA, that is, the temperature monitor circuit is inverted. If sufficient effect by the feedback resistor R ₄ is obtained, it is not necessary to provide a feedback resistor R _5.
The resistor R _{4 in} FIG. 1 can be replaced with a constant current source S ₁ that passes a predetermined current, as shown in FIG. Further, the temperature monitor circuit can be basically configured by a PNP type bipolar transistor, and various embodiments can be adopted for the specific circuit configuration, the polarity of the power supply voltage, and the like.

In the above description, the case where the invention made by the present inventor is mainly applied to the temperature monitor circuit included in the automatic power-off mechanism of the computer system which is the background field of application has been described, but the invention is not limited thereto. However, the present invention is also applicable to, for example, a temperature monitor circuit formed as a single unit, an automatic power-off mechanism of other various systems, and various devices including a similar temperature monitor circuit. The present invention relates to a temperature monitor circuit including at least two constant current sources that form a reference potential and a temperature monitor potential and a differential amplifier circuit that receives these reference potential and temperature monitor potential, and an apparatus including such a temperature monitor circuit. Widely applicable to.

[0037]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows. That is, a first transistor that receives a predetermined constant voltage at its base and a second resistance means, one of which is coupled to the emitter of the first transistor, is used to cause a predetermined current to flow through the first resistance means. A first constant current source for forming a predetermined reference potential; a second transistor for receiving the constant voltage at its base; and a third resistance means, one of which is coupled to the emitter of the second transistor. A second constant current source that forms a temperature monitor potential by applying a predetermined current to a diode that serves as a detection element;
A temperature monitor circuit including a differential amplifier circuit that receives the reference potential at one input terminal thereof and the temperature monitor potential at the other input terminal thereof, and the other of the first and second resistance means commonly coupled to each other. A current feedback path including a fourth resistance means provided between the second power supply voltage and a fifth resistance means provided between the constant voltage supply point and the base of the second transistor is added. By suppressing the potential change of the reference potential of the temperature monitor circuit due to the change of the process variation represented by the saturation current of the diode, the slope of the amount of change in the potential of the temperature monitor potential is made gentle, and the reference potential and the temperature monitor potential are changed. The difference in the amount of change in potential, that is, the slope of the amount of change in potential seen as the entire temperature monitor circuit can be made gentle. As a result, it is possible to suppress changes in the temperature identification point of the temperature monitor circuit due to process variations.
It is possible to stabilize the operation of the automatic power-off mechanism including the temperature monitor circuit and promote the high performance of the computer system including the automatic power-off mechanism.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a temperature monitor circuit to which the present invention is applied.

FIG. 2 is a circuit diagram showing a second embodiment of a temperature monitor circuit to which the present invention is applied.

3 is a characteristic diagram showing an embodiment for explaining a relationship between a reference potential and a temperature monitor potential and a saturation current of a diode in the temperature monitor circuit of FIG.

FIG. 4 is a characteristic diagram showing an embodiment for explaining a relationship between a temperature identification point of the temperature monitor circuit of FIG. 1 and an in-apparatus temperature.

FIG. 5 is a circuit diagram showing an example of a temperature monitor circuit developed by the inventors of the present application prior to the present invention.

6 is a characteristic diagram showing an example for explaining a relationship between a reference potential and a temperature monitor potential in the temperature monitor circuit of FIG. 5 and a saturation current of a diode. T _{1 to} T ₂ ... NPN type bipolar transistor, D
_{1 to} D ₃ ... Diode, R _{1 to} R ₅ ... Resistor, D
A ... Differential amplifier circuit. S ₁ ... Constant current source.

Claims (4)

[Claims] 1. A first constant current source for forming a predetermined reference potential by flowing a predetermined current through a first resistance means, and a predetermined temperature monitor for supplying a predetermined current through a predetermined temperature detecting element. A second constant current source that forms a potential, a differential amplifier circuit that receives the reference potential at one input terminal thereof and the temperature monitor potential at the other input terminal, and the first and second
And a current feedback path provided between the constant current sources of the temperature monitor circuit. 2. A first transistor, wherein said first constant current source receives a predetermined constant voltage at its base, and has its collector coupled to a first power supply voltage via said first resistance means, One of which includes a second resistance means coupled to the emitter of the first transistor,
Of the constant current source of the second transistor, the base of which receives the constant voltage, the collector of which is coupled to the first power supply voltage through the temperature detection element, and the one of which is an emitter of the second transistor. Third resistance means coupled to the fourth feedback means, wherein the current feedback path is provided between the other of the second and third resistance means and the second power supply voltage. The temperature monitor circuit according to claim 1, comprising: 3. The current feedback path comprises a fifth resistance means provided between the constant voltage supply point and the base of the second transistor. 2 temperature monitor circuit. 4. The temperature detecting element comprises a predetermined number of diodes arranged in series, and the temperature monitor circuit is included in an automatic power-off mechanism of a computer system. The temperature monitor circuit according to claim 1, claim 2, or claim 3.