JP2932545B2 - Reference voltage generation circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference voltage generation circuit, and more particularly, to a reference voltage generation circuit that provides a comparator or the like that determines the level of various signals with a threshold level serving as a reference for the determination.

2. Description of the Related Art Conventionally, comparators have been widely used as circuits for determining signal levels of various signals. This comparator compares the levels of two input signals and outputs a high-level signal or a low-level signal. When it is determined whether or not various signals are at or above a predetermined level, one comparator is used. A threshold level signal serving as a reference for determination is supplied to an input terminal, and the level of a signal input to another input terminal is determined.

In addition, with the progress of semiconductor technology in recent years,
As the use of ICs is progressing, a circuit including a comparator for judging a signal level is also widely adopted as a circuit including an IC.

Here, the comparator that determines the signal level is used in various fields, and is used, for example, in a lamp disconnection detecting device of a vehicle. An example of a conventional lamp disconnection detecting device for a vehicle will be described with reference to FIG.

In the figure, a current path developing in the disconnection detection resistor R _s to a plurality of lamps 12 is interposed from the battery 10, a comparator 16 which is disposed within IC14 converts the current to a voltage flowing through the lamp 12
To the non-inverting input terminal.

On the other hand, the reference voltage V _R which gives the threshold level is input to the inverting input terminal of the comparator 16. In this example, the voltage drops by the internal power supply V ₁ from the positive side voltage of the battery 10 is supplied as a reference voltage.

Therefore, when the current lamp 12 flows through the sense resistor R _s broken is lower than the current value (threshold current I _th) in the resistance R _s when the output of the comparator 16 is inverted,
The voltage input to the non-inverting input terminal of the comparator 16 becomes lower than the reference voltage input to the inverting input terminal, the output of the comparator 16 changes from a low level to a high level, and the disconnection detection signal _Sd is output.

Here, the threshold current I _th usually requires accuracy of several%, for example, about ± 4%, but R _s , the internal power supply V _{1 of the} IC, and the like tend to further vary.
As shown in the figure, resistors R _V1 and R _V2 are connected to the outside of the circuit 14 and the threshold current I _th is changed by adjusting these resistance values.

FIG. 8 shows a configuration example of another conventional disconnection detecting device. In this example, the external resistance of the IC 14 is only one R _V. Then, adjust the output voltage of the internal power supply V ₁ of the IC14 in the IC with divide by two divider resistors R ₁ and R _2, the level of the divided output by the resistance value of the external resistor R _V doing. A conventional lamp disconnection detecting device is disclosed, for example, in Japanese Utility Model Application Laid-Open No. 61-169837.

[Problems to be Solved by the Invention] However, according to the conventional device shown in FIG.
Requires two external resistors R _V1 and R _V2 , which increases the space occupied on the printed circuit board and increases the cost of parts.

On the other hand, if the configuration shown in FIG. 8 is adopted, only one external resistor is required, and the above disadvantage can be solved. However, when such a structure is employed, determine for dividing resistors R ₁ and R ₂ in the IC14 has a large temperature coefficient of typically several thousand ppm / ° C., detection current flowing through the resistor R _s is normal The threshold current I _th greatly changes with temperature.
There was a problem that accurate judgment could not be made.

That is, with the configuration of Figure 8, the current in resistor R _s when the output of the comparator 16 is inverted (threshold current I _th) is expressed as follows.

I _th = (1 / R _s ) ・ {(R ₂ + R _V ) / (R ₁ + R ₂ + R _V )} ・
V Then, the resistance ratio (R ₁ + R _V ) / (R ₁ + R ₂ + R _V ) changes according to the change of the temperature (chip temperature) of the IC 14, and the threshold current I _th changes.

For example, if R ₁ = 4.7 kΩ, R ₂ = 3.3 kΩ, temperature coefficient of resistance value +2000 ppm / ° C., and R _V = 4.7 kΩ, the resistance ratio to the chip temperature (R ₂ + R _V ) / (R ₁ + R ₂ + R _V ) has a ninth temperature coefficient.
As shown in the figure, it becomes about -400 to -500 ppm / ° C. In order for the comparator 16 to operate normally, the temperature coefficient is required to be ± 200 to 300 ppm / ° C. or less.

That is, when the temperature decreases, the reference voltage input to the non-inverting input terminal of the comparator 16 increases due to the temperature characteristics of the resistance ratio. Therefore, any of the lamps 12 is also not broken, the resistance detection current flowing through the R _s is despite a normal, relatively detection current erroneous of cause lamp breakage due to be considered as dropped The detection signal is output from the comparator 16. Further, when the temperature rises, the reference voltage decreases, so that even if the lamp is disconnected, it cannot be detected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a reference voltage generating circuit capable of generating a stable reference voltage with respect to a temperature change.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method of connecting a temperature compensating resistor having an impurity concentration different from a voltage dividing resistor to the voltage dividing resistor on the IC substrate. The temperature characteristic of the reference voltage can be set according to the impurity concentration difference between the piezoresistor and the temperature compensating diffusion resistor.

According to the present invention configured as described above, the temperature characteristics of the reference voltage can be set by adjusting the relative impurity concentration difference between the voltage dividing resistor and the temperature compensating resistor. Even if a change occurs, the reference voltage can be kept constant by canceling the change in the resistance value.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

First Embodiment FIG. 1 shows the configuration of a first embodiment of the present invention.

In the figure, the conventional example as well as the lamp 12 and the connection point of the resistors R _s for current detection is connected to the non-inverting input terminal of the comparator 16, and inputs a voltage corresponding here to the detected current.

Then, the internal power supply V ₁ was in the interior of the IC 14, the partial pressure formed by the impurity diffusion resistors R ₁ and the temperature compensating resistor divider R _r is provided, an internal power supply V ₁ by the connection of the external resistance R _V
Voltage is divided. Therefore, it is possible to supply the reference voltage V _R which fell predetermined value than the voltage Vcc of the power supply 10 to the non-inverting input terminal of the comparator 16.

Then, any one of the plurality of lamps 12 is disconnected, the current flowing here is reduced, detects the current flowing through the resistor R _s is equal to or less than the threshold current I _th of the foregoing. That is, the resistance voltage drop across R _s is reduced, is the input voltage at the non-inverting terminal of the comparator 16 becomes the reference voltage V _R or supplied to the inverting input terminal. As a result, the output of the comparator 16 is inverted to a high level, and the lamp disconnection detection signal _Sd is output.

Here, feature of the present invention, the partial pressure resistors for temperature compensation having different temperature characteristics from the dividing resistor R ₁ in IC14
The R _r provided in the IC 14, whereby in that to prevent fluctuation of the reference voltage V _R due to a temperature change of the IC 14.

Accordingly, it described variation preventing the reference voltage V _R.

The output voltage of the internal power supply V ₁ was resistors R ₁ and R _V, is divided according to parallel with the resistance value of R _r, which is a voltage drop from the power supply voltage Vcc, an inverting input terminal of the comparator 16 as the reference voltage V _R Supplied to

V _R = V ₁ · R _r R _V / (R ₁ + R _r R _V ) where R _r R _V represents a parallel combined resistance, and R _r R _V = 1 /
(1 / _Rr + 1 / _RV ).

Therefore, by adjusting the size of the external resistor R _V, it is possible to adjust the magnitude of the reference voltage V _R.

Here, the temperature coefficient of the voltage dividing resistor formed inside the IC 14 by impurity diffusion differs depending on the impurity concentration. As shown in FIG. 2, the temperature coefficient generally increases as the impurity concentration decreases. Therefore, the setting of the temperature characteristics of the compensating voltage dividing resistor _Rr can be performed by increasing or decreasing the impurity concentration.

That is, the temperature coefficient of the voltage dividing resistor R ₁ is a ₁ , the temperature coefficient of the temperature compensating voltage dividing resistor R _r is a _r , and the temperature coefficient of the DC power supply V ₁ is a
Assuming that (V ₁ ) and T is the temperature, each temperature coefficient is expressed as follows.

_{a 1 = 1 / R 1 ·} dR 1 / dT, whereas _{a r = 1 / R r ·} dR r / dT, a (V 1) = 1 / V 1 · dV / dT, for simplicity, the R _V It is assumed that the temperature coefficient is 0. This is the external resistor R _V is made of, for example, a metal film resistor, ± 100 ppm / ° C. or less, -400～0Ppm also a carbon film resistor
/ ° C., which is smaller than the temperature coefficient of the internal resistance of the IC 14, and there is no problem even if the temperature coefficient is considered to be 0.

In this way, the temperature coefficient of V _R a (V _R) is given by the following equation.

_{a (V R) = a (} V 1) + R 1 (a (R A) -a 1) / (R 1 + R A) _{wherein, R A = R r R V} , a (R A) = R V · a _r / (R _V + R _r ), where _ar is the temperature coefficient of the temperature compensation resistor R _r .

As is apparent from the above equation, by setting the temperature coefficient a (R _r ) of the temperature compensating voltage dividing resistor _Rr to a predetermined value, the temperature characteristic of the temperature coefficient a (R ₁ ) of the voltage dividing resistor R ₁ can be improved. The temperature characteristic a (V _R ) of the cancellation and the reference voltage V _R can be set to a predetermined value.

The second embodiment basically can suppress the influence of IC temperature with respect to the reference voltage V _R as described above. However, the temperature-compensating voltage dividing resistor R _r
Since the impurity concentration of the resistor is fixedly determined in advance in the step of forming the resistor on the substrate, the variation of the reference voltage V _R can be suppressed exactly in correspondence with the decrease in the resistance value of the voltage dividing resistor R _1. It is not easy to set the resistance value.

For this, the third two temperature compensating voltage dividing resistor for the temperature compensating resistor R _r, as shown in FIGS R _r1 and R _r2 adopted, dividing resistors R ₁ and one of the resistance R _r1 of which The same impurity concentration is used, and only the other resistor _Rr2 is configured to change the impurity concentration.

With this configuration, it is easier to set the resistance value of the temperature-compensating voltage dividing resistor _Rr as a whole than in the embodiment shown in FIG.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG.

In the present embodiment, it is further connected other voltage dividing resistors R ₃ and R ₄ in series between the external and the temperature compensating resistor divider R _r resistor R _V, from between the both resistors R _3, R ₄ reference voltage V _R is taken out.

Here, similarly to the second embodiment, the temperature-compensating voltage dividing resistor is used.
R _r consists parallel resistance of R _r1 and R _r2, a relationship of _{R r} = R _r1 R _2.

Then, the reference voltage V _R is given by the following equation.

V _R = V ₁ · ｛R _r (R ₃ + R ₄ + R _V )｝ / [｛R ₁ + ｛R _r (R ₃ + R ₄ + R _V )｝] · (R ₄ + R _V ) / (R ₃ + R ₄₎ + R _V) where is _{R r1 R r2 = 1 / (} 1 / R r1 + 1 / R r2).

Then, as described above, R _r2 is formed by a diffusion process different from the other _{voltage dividing} resistors, and the impurity concentration thereof is set lower than the others. For this reason, the resistor _Rr2 has a higher temperature coefficient than the other _{voltage dividing} resistors. Therefore, canceling the negative temperature coefficient of the reference voltage V _R generated during temperature variation of IC 14, it is possible to produce a stable reference voltage V _R with respect to temperature.

 Here, this will be described using an equation.

First, the temperature coefficient of the voltage dividing resistors R ₁ · R ₃ and R ₄ a _1, the temperature coefficient of the temperature compensation voltage dividing resistor R _r a _r, the temperature coefficient of the DC power supply V ₁ and a (V ₁₎ . When the temperature is T, the following relationship is established.

a ₁ = 1 / R ₁ · dR ₁ / dT, a _r = 1 / R _r · dR _r / dT, a (V ₁ ) = 1 / V ₁ · dV ₁ / dT Also, as in the above case, It is assumed that the temperature coefficient of R _V is 0.

In this way, the temperature coefficient of V _R a (V _R) is given by the following equation.

a (V _R ) = a (V ₁ ) + R ₁ (a (R _A ) −a ₁ ) / (R ₁ + R _A ) + ΔR ₄ / (R ₄ + R _V ) − (R ₃ + R ₄ ) / ( R ₃ + R ₄ + R _V )｝ a ₁ where R _A = R _r (R ₃ + R ₄ + R _V ), a (R _A ) = ｛(R ₃ + R ₄ + R _V ) _ar + R _r · a ₁ ( _{R 3 + R 4) / (} R 3 + R 4 + R V)} / (R r + R 3 + R 4 + R V) where the temperature coefficient of a _r is _{R r = R r1 R r2,} a r = (R r2 · _{a 1 + R r1 · a r2} ) / (R r1 + R r2), also, a _r2 represents the temperature coefficient of R _r2.

Further, the temperature coefficient of R _r1 is a ₁ the same as the temperature coefficient of the other voltage dividing resistors.

As is clear from the above equation, even if the manufacturing conditions of the _{voltage dividing} resistor are not changed, if the temperature coefficients of the temperature compensating _{voltage dividing} resistors R _r1 and R _r2 are known in advance, the resistance pattern can be changed by changing the resistance pattern.
_r1, and adjusting the ratio of R _r2 arbitrarily to adjust the temperature coefficient a ₂ and, therefore the temperature coefficient a (V _r) of the reference voltage V _R can also be adjusted to the desired value.

As an example, a (V ₁ ) = 0, a ₁ = 2000 ppm / ° C., a ₁ = 44
_{00ppm / ℃, R 1 = 8.8kΩ} , R r1 = 0.96kΩ, R r2 = 4.8kΩ, R
_{V for} the value of R _V when ₃ = 4.0 kΩ and R ₄ = 3.3 kΩ
FIG. 5 shows the change in the temperature coefficient a (V _r ) of _R.

FIG As is apparent from, the temperature coefficient a (V _R) is changed by the value of R _V, the range of R _V in _{1kΩ ≦ R V ≦ 20kΩ, |} a
(V _R ) | ≦ 100 ppm / ° C. is obtained, and the reference voltage V _{R is} extremely small in temperature dependency as compared with the conventional device indicated by the broken line.
Can be obtained.

Fourth Embodiment In the above embodiment, the voltage Vcc potential is used as a reference. However, the voltage Vcc may be used as a reference. FIG. 6 shows a reference voltage VR generation circuit based on the GND potential. In this example, only the reference for setting the voltage is different, and the operation of each unit is exactly the same as in the above-described embodiment.

In the above embodiments, only has caused the reference voltage V _R by the resistance partial pressure, it is also possible to further add an OP amp (operational amplifier), constituting a combination of inverting and non-inverting amplifier .

Further, the reference voltage may be dependent on the power supply voltage or other input, for example, may be changed according to the input frequency as used in F / V conversion.

[Effects of the Invention] As described above, according to the present invention, by disposing a temperature-compensating voltage-dividing resistor in an IC, the fluctuation of the reference voltage and current caused by the temperature rise of the IC is absorbed and the temperature dependency is reduced. Low threshold current, and adjust the voltage value.
It can be easily adjusted only by the external resistance of the IC.

Further, the circuit configuration can be simplified, and the temperature coefficient can be arbitrarily adjusted by changing the value of the voltage-dividing resistor, so that the temperature coefficient can be easily adjusted by simple calculation and pattern correction.

In addition, since only one external resistor for adjusting the output voltage of the IC is required, it is advantageous in terms of cost and board space.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, FIG. 2 is a characteristic diagram showing a relationship between an impurity concentration of a voltage dividing resistor and a temperature coefficient, and FIG. 3 is a second embodiment of the present invention. circuit diagram showing, Figure 4 is a third embodiment of the circuit configuration diagram showing, Fig. 5 characteristic diagram showing the relationship between the reference voltage V _R to the magnitude of the external resistor and the output of the present invention, Figure 6 is 7 and 8 are circuit diagrams of a conventional device, and FIG. 9 is a diagram showing a relationship between an external resistor and a temperature coefficient of an output reference voltage of the conventional device. It is a characteristic diagram. 12 …… Lamp 14 …… IC 16 …… Comparator R ₁ , R ₃ , R ₄ …… Voltage dividing resistor R _r … Temperature compensating voltage dividing resistor R _v …… External resistor R _s …… Disconnection detection resistor V _R …… Reference voltage

Claims (1)

(57) [Claims] 1. A voltage dividing resistor formed on an IC substrate by a diffusion process and supplied with a predetermined DC voltage, and an external resistor externally connected to the IC for adjusting a reference voltage output from the voltage dividing resistor. And connecting a temperature compensating resistor formed on the IC substrate by a diffusion process and having an impurity concentration different from the voltage dividing resistor to the voltage dividing resistor on the IC substrate. A reference voltage generation circuit, wherein temperature characteristics of a reference voltage can be set according to an impurity concentration difference between a piezoresistor and a temperature compensation resistor.