Temperature sensor device

Abstract

To provide a temperature sensor device which is capable of measuring fine temperature variations without requiring a high-performance IC tester and can be manufactured at low cost.SOLUTION: A temperature sensor device is provided, comprising a temperature sensor circuit 2 and a test temperature sensor 1. The test temperature sensor 1 comprises a PN junction element 15 acting as a temperature sensing element, a variable current source configured to supply at least two levels of different forward currents to the PN junction element 15, and a constant voltage source 16 for outputting a constant voltage having the same temperature characteristics as a forward voltage across the PN junction element 15.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a temperature sensor device. [Background technology]

[0002] Temperature sensors used in various applications are required to measure minute temperature changes. For example, there are cases where the temperature detection accuracy must be higher than 1°C.

[0003] 5 is a circuit diagram showing a conventional temperature sensor. The conventional temperature sensor determines the temperature from the difference in forward voltage when currents of different current values ​​are passed through a diode, which is a temperature sensitive element (see, for example, Patent Document 1).

[0004] The difference in voltages output by the temperature sensor, ΔVo (Vo1-Vo2), is expressed as A(kT / q)ln(N), where Vo1 is the voltage obtained by amplifying the forward voltage Vf1 when a forward current I1 flows through the diode, Vo2 is the voltage obtained by amplifying the forward voltage Vf2 when a forward current I2 flows through the diode, k is the Boltzmann constant, T is the absolute temperature, q is the electron charge, A is the amplification factor of the amplifier, and N is the forward current ratio I1 / I2.

[0005] Therefore, temperature T is expressed as qΔVo / {kAln(N)}, and temperature coefficient dΔVo / dT is expressed as dΔVo / dT = A(k / q) ln(N). k = 1.38 x 10^-23 [J / K], q = 1.60 x 10^-19 [C], and if N = 2, the temperature coefficient dΔVo / dT is approximately A x 60 [uV / K].

[0006] Conventional temperature sensors such as those described above can measure temperature with high accuracy because the difference in the forward voltages of diodes is directly proportional to absolute temperature. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Pat. No. 3,812,717 Summary of the Invention [Problem to be solved by the invention]

[0008] However, IC testers used for shipping inspections generally have an applied temperature resolution of 1°C or higher. Therefore, if a temperature sensor is used in a product that measures minute temperature changes, a high-performance IC tester that applies temperature with high resolution during the inspection process is required, resulting in high manufacturing costs.

[0009] Furthermore, if it is necessary to measure a minute temperature change, for example a temperature change of 0.1K, the temperature coefficient dΔVo / dT is A×6 [uV / 0.1K]. In this case, to make the voltage change measurable with a general voltmeter such as an IC tester (temperature coefficient 600uV / 0.1K), the amplifier's amplification factor A must be 100 or more. On the other hand, if the diode forward voltages Vf1 and Vf2 are around 0.6V at a certain temperature, the output voltage of an amplifier with an amplification factor A of 100 or more will be 60V or more. In other words, to measure the voltage output by this amplifier, it is necessary to measure high voltages with high precision.

[0010] Therefore, conventional temperature sensors require a high-performance voltmeter in the IC tester used in the inspection process, which increases the manufacturing cost. One possible solution to this problem is to digitally process the output voltage of a conventional temperature sensor before outputting it.

[0011] However, conventional temperature sensors increase accuracy by calculating the temperature from two forward voltage values, which creates new issues such as the need for larger registers to store the temperature data required for digitization, which increases product costs.

[0012] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a temperature sensor device that is capable of measuring minute temperature changes, does not require a high-performance IC tester, and can be manufactured at low cost. [Means for solving the problem]

[0013] The temperature sensor device of the present invention comprises a temperature sensor circuit and an inspection temperature sensor. The inspection temperature sensor comprises a PN junction element which is a temperature-sensitive element, a variable current source which supplies at least two different values ​​of forward current to the PN junction element, and a constant voltage source which outputs a constant voltage having the same temperature characteristics as the forward voltage of the PN junction element. Effect of the Invention

[0014] According to the present invention, it is possible to provide a temperature sensor device that is capable of measuring minute temperature changes, does not require a high-performance IC tester, and can be manufactured at low cost. [Brief description of the drawings]

[0015] [Figure 1] 1 is a block diagram showing a temperature sensor device including an inspection temperature sensor according to the present invention; [Diagram 2] 4 is a graph showing temperature characteristics of forward voltages Vf1, Vf2 and constant voltage Vb of the inspection temperature sensor of the present embodiment. [Diagram 3] FIG. 2 is a circuit diagram showing an example of a temperature sensor circuit of the temperature sensor device of the present embodiment. [Figure 4] FIG. 2 is a circuit diagram illustrating an example of a temperature sensor according to the present embodiment. [Diagram 5] FIG. 1 is a circuit diagram showing a conventional temperature sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, a temperature sensor device 100 including an inspection temperature sensor 1 of the present invention will be described with reference to the drawings.

[0017] FIG. 1 is a block diagram showing a temperature sensor device 100 including an inspection temperature sensor 1 according to this embodiment. The temperature sensor device 100 includes an inspection temperature sensor 1, a temperature sensor circuit 2, and output terminals T1 to T3. The temperature sensor as a product of the temperature sensor device 100 is included in the temperature sensor circuit 2.

[0018] The inspection temperature sensor 1 includes constant current sources 11 and 12, switches 13 and 14, a diode 15 which is a temperature sensitive element, and a constant voltage source 16. The constant current sources 11 and 12 and the switches 13 and 14 form a variable current source.

[0019] The constant current source 11 has one end connected to a power supply terminal and the other end connected to one end of the switch 13. The constant current source 12 has one end connected to a power supply terminal and the other end connected to one end of the switch 14. The diode 15 has an anode connected to the other end of the switch 13, the other end of the switch 14 and terminal T1, and a cathode connected to the ground terminal. The constant voltage source 16 has one end connected to terminal T2 and the other end connected to the ground terminal. The temperature sensor circuit 2 has an output terminal connected to the terminal T3.

[0020] The constant current source 11 outputs a constant current I1. The constant current source 12 outputs a constant current I2 having a current value different from the constant current I1. The diode 15 generates a forward voltage Vf1 when the constant current I1 is supplied, and generates a forward voltage Vf2 when the constant current I2 is supplied, and outputs the voltages to the terminal T1.

[0021] Constant voltage source 16 outputs to terminal T2 a constant voltage Vb having the same temperature characteristics as forward voltage Vf of diode 15. Constant voltage source 16 is configured to output as constant voltage Vb a forward voltage generated when a constant current slightly smaller than constant currents I1 and I2 flows through a diode of the same type as diode 15. Constant voltage Vb is set to a value slightly lower than forward voltages Vf1 and Vf2, for example.

[0022] The inspection device is a general IC tester and includes a control device and an amplifier. The control device includes a measuring device such as a voltmeter and a memory. For example, the amplifier has a non-inverting input terminal connected to the anode of a diode 15 via a terminal T1, an inverting input terminal connected to an output terminal of a constant voltage source 16 via a terminal T2, and an output terminal connected to the control device.

[0023] Here, the constant voltage Vb is set to a value that allows the voltage obtained by amplifying the difference between the forward voltages Vf1 and Vf2 of the diode 15 with an amplifier to be measured with a voltmeter of a typical IC tester. In other words, the constant voltage Vb is set in consideration of the forward voltages Vf1 and Vf2 of the diode 15, the amplification factor of the amplifier, the capacity of the voltmeter of the testing device, etc.

[0024] The temperature sensor device 100 configured as described above can inspect the accuracy of the temperature sensor circuit 2, which is a product temperature sensor, based on the temperature data output by the inspection temperature sensor 1, which is capable of measuring temperature with high accuracy. Furthermore, the amplifier of the inspection device may have a small amplification factor because it amplifies the difference between the forward voltage Vf1 output by the inspection temperature sensor 1 and the constant voltage Vb, and the difference between the forward voltage Vf2 and the constant voltage Vb. Therefore, the voltmeter of the inspection device only needs to measure small voltages with high accuracy, and does not need to be high performance.

[0025] The operation of the inspection temperature sensor 1 according to this embodiment will be described. First, the switch 13 is turned on and the switch 14 is turned off to supply the constant current I1 from the constant current source 11 to the diode 15. When the constant current I1 flows as a forward current through the diode 15, the forward voltage generated in the diode 15 is defined as Vf1. The forward voltage Vf1 corresponds to the temperature when the constant current I1 flows through the diode 15.

[0026] Next, switch 13 is turned off and switch 14 is turned on to supply constant current I2 from constant current source 12 to diode 15. When constant current I2 flows as a forward current through diode 15, a forward voltage generated in diode 15 is defined as Vf2. The forward voltage Vf2 corresponds to the temperature when constant current I2 flows through diode 15.

[0027] Forward voltages Vf1 and Vf2 generated in diode 15 are output to terminal T1 and input to the non-inverting input terminal of the amplifier of the inspection equipment. Voltage Vb output by constant voltage source 16 is output to terminal T2 and input to the inverting input terminal of the amplifier of the inspection equipment. The amplifier amplifies the difference between forward voltage Vf1 and voltage Vb with an amplification factor A, and also amplifies the difference between forward voltage Vf2 and voltage Vb with an amplification factor A, and outputs them to the control device.

[0028] FIG. 2 is a graph showing the temperature characteristics of the forward voltages Vf1, Vf2 and the constant voltage Vb of the inspection temperature sensor 1 of this embodiment. In this embodiment, the relationship between the constant current I1 and the constant current I2 is I1>I2, that is, the relationship between the forward voltage Vf1 and the forward voltage Vf2 is Vf1>Vf2. The forward voltages Vf1 and Vf2 are both forward voltages generated in the diode 15, and therefore have the same temperature characteristics. The constant voltage Vb is generated in the circuit of the constant voltage source 16 described later, and has the same temperature characteristics as the forward voltages Vf1 and Vf2, but is slightly lower than them.

[0029] A method for determining the temperature from the output voltage of the inspection temperature sensor 1 configured as above will be described below. The inspection temperature sensor 1 outputs forward voltages Vf1 and Vf2 and a constant voltage Vb when forward currents I1 and I2 are passed through the diode 15. The inspection device obtains the temperature from the voltage obtained by amplifying the difference between these output voltages with an amplifier.

[0030] When a forward current I flows through a diode, the forward voltage Vf is expressed by the following equation. Vf = (kT / q) × ln(I / Is) … (1) (k is the Boltzmann constant, T is the absolute temperature, q is the electron charge, and Is is the saturation current).

[0031] From equation (1), the forward voltage Vf1 and forward voltage Vf2 of the diode are expressed by the following equations. Vf1=(kT / q)×ln(I1 / Is) … (2) Vf2=(kT / q)×ln(I2 / Is) … (3)

[0032] The difference between the forward voltage Vf1 and the constant voltage Vb, and the difference between the forward voltage Vf2 and the constant voltage Vb are each amplified by an amplifier with an amplification factor A. The output voltages of the amplifiers are represented by the following equations, where Vo1 and Vo2 are the output voltages of the amplifiers, respectively. Vo1=A{(kT / q)×ln(I1 / Is)-Vb} … (4) Vo2=A{(kT / q)×ln(I2 / Is)-Vb} … (5)

[0033] If the ratio of the forward currents I1 and I2 is N:1, the difference ΔVo in the amplifier output voltage is expressed by the following equation. ΔVo=Vo1-Vo2=A(kT / q)×ln(N) … (6)

[0034] From equation (6), we can see that by taking the difference in the amplifier's output voltage, the term for the constant voltage Vb as well as the term for the diode saturation current Is can be eliminated. Moreover, the absolute temperature T is expressed by the following formula. T=q×ΔVo / {A×k×ln(N)} … (7)

[0035] Therefore, the temperature can be calculated by measuring the amplifier output voltages Vo1 and Vo2 with a voltmeter and using equation (7). Moreover, by differentiating both sides of equation (7), the temperature coefficient dΔVo / dT can be obtained. dΔVo / dT=A×(k / q)×ln(N) … (8)

[0036] Assuming k = 1.38 x 10^-23 [J / K], q = 1.60 x 10^-19 [C], and N = 2, the temperature coefficient dΔVo / dT is expressed by the following equation from equation (8). dΔVo / dT≒A×60[uV / K] … (9)

[0037] Now, if it is necessary to measure a minute temperature change, for example a temperature change of 0.1K, the temperature coefficient is A x 6 [uV / 0.1K] from equation (9). In this case, to make the voltage change (temperature coefficient 600uV / 0.1K) measurable with a general voltmeter such as an IC tester, the amplifier's amplification factor A is set to 100 or more. Here, if the diode forward voltages Vf1 and Vf2 are about 0.6V at a certain temperature and the constant voltage Vb is set to 0.594V, the output voltage of an amplifier with an amplification factor A of 100 will be about 0.6V because it is amplifying the difference, 0.006V, between the forward voltages Vf1 and Vf2 and the constant voltage Vb.

[0038] As described above, the inspection temperature sensor 1 of this embodiment is capable of accurately measuring minute temperature changes (temperature coefficient 600 uV / 0.1 K) even though the voltage amplified by the amplifier of the inspection device is about 0.6 V.

[0039] Therefore, the inspection device used in the inspection process can inspect the temperature sensor circuit 2 based on the temperature calculated from the output voltage of the inspection temperature sensor 1 of this embodiment. That is, the inspection device does not require a high-performance IC tester that applies temperature with high resolution, which can reduce manufacturing costs. Furthermore, since the voltage amplified by the amplifier is about 0.6 V, the inspection device does not require a high-performance voltmeter, which reduces manufacturing costs.

[0040] FIG. 3 is a circuit diagram showing an example of the temperature sensor circuit 2 of the temperature sensor device 100 of this embodiment. The temperature sensor circuit 2 includes a temperature sensor 21, an AD converter 22, an oscillator circuit 23, an interface 24, a register 25, and a control circuit 26. By using a digital temperature sensor, the temperature sensor circuit 2 can easily achieve high detection accuracy, and since the output is a digital signal, testing is also easy.

[0041] FIG. 4 is a circuit diagram showing an example of the temperature sensor 21 of the present embodiment. The temperature sensor 21 includes a constant current source, a diode which is a temperature sensitive element, and an amplifier.

[0042] Since the temperature sensor 21 uses the temperature sensor circuit 2 as a digital temperature sensor, it is desirable to use a circuit configuration that does not increase the size of the digital conversion section. The temperature sensor 21 shown in Fig. 4 does not use a method of calculating the temperature from a binary forward voltage as in the inspection temperature sensor 1, so it is possible to reduce the register size of the digital conversion section.

[0043] As described above, the temperature sensor device 100 of this embodiment is capable of measuring minute temperature changes while keeping manufacturing costs low.

[0044] Since the temperature sensor device 100 includes a highly accurate inspection temperature sensor 1, it is not necessary to use a high-performance IC tester that applies temperature with high resolution in the inspection device, and therefore the manufacturing cost can be reduced. In addition, the amplifier of the inspection device may have a small amplification factor because it amplifies the difference between the forward voltage Vf1 output by the inspection temperature sensor 1 and the constant voltage Vb, and the difference between the forward voltage Vf2 and the constant voltage Vb. Therefore, the inspection device does not require a high-performance voltmeter, and the manufacturing cost can be reduced.

[0045] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and in the implementation stage, it is possible to implement the present invention in various forms other than the above-described embodiments, and various omissions, additions, substitutions, or modifications can be made without departing from the spirit of the invention.

[0046] For example, in the embodiment, the temperature-sensing element is a diode, but it is not limited to this and may be any PN junction element. Also, the forward voltage Vf of the diode is about 0.6 V, and the constant voltage Vb having the same temperature characteristic as the forward voltage Vf of the diode is 0.594 V, but it is not limited to this. Also, the variable current source is described as supplying two different current values ​​to the diode, but it is not limited to this and temperature measurement may be performed using three or more different current values. [Explanation of symbols]

[0047] 1 Inspection temperature sensor 2 Temperature sensor circuit 11, 12 Constant current source 13, 14 Switch 15 Diodes 16 Constant voltage source 21 Temperature Sensor 22 AD converter 23 Oscillator Circuit 24 Interface 25 Registers 26 Control circuit

Claims

1. A temperature sensor circuit and an inspection temperature sensor are provided. The inspection temperature sensor is a PN junction element which is a temperature-sensitive element; a variable current source that supplies at least two different values ​​of forward current to the PN junction element; a constant voltage source that outputs a constant voltage having the same temperature characteristics as the forward voltage of the PN junction element; A temperature sensor device comprising:

2. The inspection temperature sensor is At least two different forward voltages of the PN junction element and the constant voltage are output.

2. The temperature sensor device according to claim 1.

3. 3. The temperature sensor device according to claim 1, wherein the constant voltage is set in consideration of at least two different forward voltages of the PN junction element, the amplification factor of an amplifier in an inspection device, and the capacity of a voltmeter.

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