JP2003344181A - Temperature sensor circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature sensor circuit for reducing noises interfusing with an output signal by an influence of the noises included in a power supply voltage. <P>SOLUTION: The temperature sensor circuit has a first voltage dividing circuit comprising a first resistor R11 having a positive temperature coefficient, and a second resistor R12 serially connected to the first resistor R11 and having a negative temperature coefficient. Further, the circuit has a first voltage dividing circuit for dividing the power supply voltage to obtain a divided voltage; a second voltage dividing circuit comprising a third resistor R13 and a fourth resistor R14 serially connected to the third resistor R13, and dividing the power supply voltage and obtaining the same divided voltage as the first voltage dividing circuit at a normal temperature; a differential circuit 25 for differentially amplifying the divided voltages from the first and the second voltage dividing circuits; and a reference voltage circuit for adding a reference voltage obtained by buffering the divided power supply voltage to an output from the differential circuit. The differential circuit cancels the noise included in the power supply voltage. The noises included in the power supply voltage and interfusing with the output signal can be reduced by adding the reference voltage as the divided power supply voltage to the output from differential circuit without amplification. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature sensor circuit, and more particularly to a temperature sensor circuit that outputs a temperature signal having a voltage according to ambient temperature.

[0002]

2. Description of the Related Art FIG. 3 shows a circuit diagram of an example of a conventional temperature sensor circuit. In the figure, the power supply voltage Vcc output from the constant voltage source 10 is supplied to one end of each of the resistors R1 and R2. The other end of the resistor R1 is connected to the non-inverting input terminal of the operational amplifier 14 which constitutes the non-inverting amplifier 12, and
The diode D1 is connected to the anode of the diode D1.
Is connected to the anode of the diode D2, and the cathode of the diode D2 is grounded.

Each of the diodes D1 and D2 has a temperature coefficient of -2 mV / ° C, and the other end of the resistor R1 and the diode D2.
The temperature coefficient at the connection point A with the anode of No. 1 is -4 mV
/ ° C. The output terminal of the operational amplifier 14 is connected to the terminal 16, and is also connected to the inverting input terminal of the operational amplifier 14 and one end of the resistor R5 via the resistor R4.

The other end of the resistor R2 is connected to one end of the resistor R3 and the non-inverting input terminal of the operational amplifier 18. The other end of the resistor R3 is grounded, and the power source voltage Vcc is divided by the resistors R2 and R3. The output terminal and the inverting input terminal of the operational amplifier 18 are short-circuited to form a buffer amplifier, and the output terminal of the operational amplifier 18 is connected to the other end of the resistor R5. The resistors R3 and R4 and the buffer amplifier generate the reference voltage Vref and supply it to the inverting input terminal of the operational amplifier 14. As a result, the non-inverting amplifier 12 including the operational amplifier 14 amplifies the voltage at the connection point A and outputs it as a temperature signal from the terminal 16.

[0005]

In the conventional temperature sensor circuit, the power supply voltage V output from the constant voltage source 10 at room temperature.
When the noise component Vn is included in cc, there is a problem that the noise component mixed in the temperature signal output from the terminal 16 becomes large.

This is because when the resistance values of the resistors R2 and R3 are the same, the reference voltage Vref output from the operational amplifier 18 becomes V.
A noise component represented by n / 2 is included, and this noise component Vn / 2 is gain A (A = 1 + R4) of the non-inverting amplifier 12.
/ R5) is amplified, and the noise component mixed in the temperature signal becomes Vn · A / 2. Note that the gain A is usually several times to several tens times, and Vn <Vn · A / 2
Therefore, the noise component increases.

The present invention has been made in view of the above points, and an object of the present invention is to provide a temperature sensor circuit capable of reducing noise mixed in an output signal due to the influence of noise included in a power supply voltage.

[0008]

According to a first aspect of the present invention, there is provided a first resistor (R11) having a positive temperature coefficient and a second resistor (R11) having a negative temperature coefficient connected in series. A first voltage divider circuit (R11, R12), which is composed of a resistor (R12) and divides the power supply voltage to obtain a divided voltage; a third resistor (R13); and a third resistor (R13) connected in series. Four
A second voltage dividing circuit (R13, R14), which is composed of a resistor (R14) and divides the power supply voltage to obtain the same voltage dividing voltage as the first voltage dividing circuit (R11, R12) at room temperature, and a first voltage dividing circuit. (R
11, R12) and the second voltage dividing circuit (R13,
Differential circuit (25) for differentially amplifying the divided voltage of R14)
And a reference voltage circuit that divides the power supply voltage and adds the reference voltage obtained by buffering to the output of the differential circuit (25) to obtain the divided voltage of the first voltage dividing circuit (R11, R12). By differentially amplifying the divided voltage of the second voltage dividing circuit (R13, R14), noise included in the power supply voltage is canceled, and the differential circuit (25 The noise included in the output signal with respect to the noise included in the power supply voltage can be reduced by adding it to the output of FIG.

The invention according to claim 2 is the third resistor (R1
Since 3) has a negative temperature coefficient and the fourth resistor (R14) has a positive temperature coefficient, the sensitivity of the temperature sensor can be increased.

It should be noted that the reference numerals in the above parentheses are given for easy understanding and are merely examples, and the present invention is not limited to the illustrated modes.

[0011]

1 is a circuit diagram of an embodiment of a temperature sensor circuit according to the present invention. In the figure, the constant voltage source 20 outputs a power supply voltage Vcc. Resistor R11 connected in series,
R12 is a voltage divider circuit that divides the power supply voltage Vcc, and similarly resistors R13 and R14 connected in series are voltage divider circuits that divide the power supply voltage Vcc.

The resistors R11 and R14 are, for example, diffusion resistors having a positive temperature coefficient and have the same resistance value. The resistors R12 and R13 are made of, for example, polysilicon resistors having a negative temperature coefficient, and have the same resistance value.

The diffusion resistance is p, as shown in FIG.
An n-type well 32 is formed on the type semiconductor substrate 30, and a p-type diffusion layer 34 is formed on the n-type well 32. Metal electrodes 35 and 36 are provided on both ends of the p-type diffusion layer 34, and the p-type diffusion layer 34 is used as a resistor.

The polysilicon resistor has an n-type well 42 formed in a p-type semiconductor substrate 40 as shown in FIG.
An insulating layer 43 is provided on the mold well 42, and a polysilicon layer 44 is formed thereon. Metal electrodes 45 and 46 are provided on both ends of the polysilicon layer 42, and the polysilicon layer 44
Is used as a resistor.

Since the resistance R11 has a positive temperature coefficient and the resistance R12 has a negative temperature coefficient, the resistance R11 increases as the ambient temperature rises.
The potential of the connection point B of 11 and R12 decreases. Also, the resistance R
Since 13 has a negative temperature coefficient and resistor R14 has a positive temperature coefficient, the potential at the connection point C between resistors R13 and R14 rises when the ambient temperature rises.

The base of the npn transistor Q1 is connected to the connection point B, and the npn transistor Q2 is connected to the connection point C.
The base of is connected. The collector of the transistor Q1 is p and the collector and base of the pnp transistor Q3.
It is connected to the base of the np transistor Q4, the emitter of the transistor Q1 is grounded via the constant current source 22, and is connected to one end of the resistor R15.

The collector of the transistor Q2 is pn
It is connected to the collector of the p-transistor Q4, the emitter of the transistor Q2 is grounded via the constant current source 24, and is connected to the other end of the resistor R15. The transistors Q3 and Q4 each have a power supply voltage Vcc supplied to their emitters to form a current mirror circuit, and the transistors Q1 and Q2 form a differential circuit 25 using the transistors Q3 and Q4 as current sources. Also, the transistor Q2
Is connected to the terminal 26 and one end of the resistor R16.

Further, resistors R17 and R18 connected in series are provided.
Divides the power supply voltage Vcc. The connection point of the resistors R17 and R18 is connected to the non-inverting input terminal of the operational amplifier 28. The output terminal and the inverting input terminal of the operational amplifier 28 are short-circuited to form a buffer amplifier.
The output terminal of is connected to the other end of the resistor R16. The resistors R17, R18 and the buffer amplifier 28 have a reference voltage V
ref is generated and supplied to the differential circuit 25 via the resistor R16.

The differential circuit 25 converts the potential difference between the connection points B and C into a current, and the converted current flows into the voltage by flowing through the resistor R16. The amplification degree A of the differential circuit 25 is represented by A = R16 / R15.

Here, the connection points B and C are at the same potential at a predetermined temperature (normal temperature) at which the resistors R11 and R12 have the same resistance value, and since no current flows through the resistor R16, the output voltage Vout of the terminal 26 is the reference voltage. It becomes Vref.

In this state, the noise component V is added to the power supply voltage Vcc.
When n is included, the potentials at the connection points B and C are (V
cc + Vn) / 2, and the noise component is canceled and removed by the differential circuit 25.

When the resistors R17 and R18 have the same resistance value, the reference voltage Vref output from the operational amplifier 28 is Vr.
ef = (Vcc + Vn) / 2, and the noise component Vn
/ 2 is included, but this noise component is not amplified by the differential circuit 25. As a result, the output voltage Vout
The noise component at is reduced to 1/2 of the noise component of the power supply voltage Vcc.

By the way, when the ambient temperature rises, the connection point B
Potential of the resistor R1 decreases and the potential of the connection point C increases.
5, a current flows from the transistor Q2 side toward the transistor Q1 side, and therefore a current flows from the resistor R16 toward the collector of the transistor Q2, whereby the sum of the voltage Vr generated at the resistor R16 and the reference voltage Vref is output. The voltage becomes Vout, and the output voltage Vout rises.
On the contrary, when the ambient temperature decreases, the output voltage Vo
ut decreases.

In the above embodiment, the resistors R11 and R1 are
Although 4 has a positive temperature coefficient and resistors R12 and R13 have a negative temperature coefficient, either one of resistors R12 and R13 has a positive temperature coefficient, or one of resistors R11 and R14 has a negative temperature coefficient. It is also possible to use a coefficient. However, the structure of the above-described embodiment has high sensitivity as a temperature sensor.

[0025]

As described above, the invention according to claim 1 is
A first voltage divider circuit comprising a first resistor having a positive temperature coefficient and a second resistor connected in series with the first resistor and having a negative temperature coefficient, for dividing a power supply voltage to obtain a divided voltage; 3 resistors,
A second voltage divider circuit, which is connected in series with the third resistor and includes a fourth resistor, which divides the power supply voltage to obtain the same divided voltage as the first voltage divider circuit at room temperature, and the divided voltage of the first voltage divider circuit. A differential circuit for differentially amplifying the divided voltage of the second voltage dividing circuit, and a reference voltage circuit for adding a reference voltage obtained by dividing and buffering the power supply voltage to the output of the differential circuit. Thus, by differentially amplifying the divided voltage of the first voltage dividing circuit and the divided voltage of the second voltage dividing circuit, noise included in the power supply voltage is canceled and the reference voltage obtained by dividing the power supply voltage is amplified. It is possible to reduce the noise included in the output signal with respect to the noise included in the power supply voltage by adding the noise to the output of the differential circuit without the need.

According to the second aspect of the present invention, the third resistor has a negative temperature coefficient and the fourth resistor has a positive temperature coefficient, whereby the sensitivity of the temperature sensor can be increased.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a temperature sensor circuit of the present invention.

FIG. 2 is a cross-sectional structure diagram of a diffusion resistance and a polysilicon resistance.

FIG. 3 is a circuit diagram of an example of a conventional temperature sensor circuit.

[Explanation of symbols]

20 constant voltage source 22, 24 constant current source 25 differential circuit 30, 40 p-type semiconductor substrate 32, 42 n-type well 34 p-type diffusion layer 35, 36, 45, 46 Metal electrodes 43 Insulation layer 44 Polysilicon layer Q1, Q2 npn transistor Q3, Q4 pnp transistor R11-R18 resistance

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5J066 AA01 AA12 CA46 FA09 HA08                       HA19 HA25 KA01 KA02 KA05                       MA13 MA21 ND12 ND23 PD01                       QA02                 5J500 AA01 AA12 AC46 AF09 AH08                       AH19 AH25 AK01 AK02 AK05                       AM13 AM21 AQ02 DN12 DN23                       DP01

Claims (2)

[Claims] 1. A first resistor comprising a first resistor having a positive temperature coefficient and a second resistor connected in series with the first resistor and having a negative temperature coefficient, for dividing a power supply voltage to obtain a divided voltage. A second voltage divider circuit, a third resistor, and a fourth resistor connected in series with the third resistor, which divides the power supply voltage to obtain the same divided voltage as the first voltage divider circuit at room temperature. A voltage circuit, a differential circuit for differentially amplifying the divided voltage of the first voltage dividing circuit and the divided voltage of the second voltage dividing circuit, and a reference obtained by dividing and buffering the power supply voltage. A temperature sensor circuit comprising a reference voltage circuit for adding a voltage to the output of the differential circuit. 2. The temperature sensor circuit according to claim 1, wherein the third resistor has a negative temperature coefficient and the fourth resistor has a positive temperature coefficient.