Semiconductor integrated circuit

Abstract

To provide a semiconductor integrated circuit capable of providing differences in characteristics.SOLUTION: The semiconductor integrated circuit according to an embodiment comprises a first terminal and a second terminal. A change in an externally applied input voltage causes change in a resistance value between the first terminal and the second terminal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a semiconductor integrated circuit. [Background technology]

[0002] For example, there are cases where multiple types of semiconductor integrated circuits are distinguished by external testing, and in such cases, if the characteristics that can be confirmed by externally testing the semiconductor integrated circuits are similar among the multiple types of semiconductor integrated circuits, it can be difficult to distinguish between the semiconductor integrated circuits. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-114337 Summary of the Invention [Problem to be solved by the invention]

[0004] The problem to be solved by the present invention is to provide a semiconductor integrated circuit capable of providing differences in characteristics. [Means for solving the problem]

[0005] The semiconductor integrated circuit of the embodiment has a first terminal and a second terminal, and a resistance value between the first terminal and the second terminal changes as an input voltage input from an external device changes. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram showing a semiconductor integrated circuit according to a first embodiment. [Figure 2] FIG. 1 is a circuit diagram showing a part of a semiconductor integrated circuit according to a first embodiment. [Figure 3] 6 is a graph showing an example of a change in resistance value between the control terminal and the ground terminal according to the first embodiment. [Figure 4]FIG. 10 is a circuit diagram showing a semiconductor integrated circuit according to a second embodiment. [Figure 5] 10 is a graph showing an example of a change in resistance value between a power supply terminal and a control terminal according to the second embodiment. [Figure 6] FIG. 10 is a circuit diagram showing a semiconductor integrated circuit according to a third embodiment. [Figure 7] FIG. 10 is a circuit diagram showing a semiconductor integrated circuit according to a fourth embodiment. [Figure 8] 10 is a graph showing an example of a change in resistance value between a control terminal and a ground terminal according to the fourth embodiment. [Figure 9] 10 is a graph showing an example of a modified example in which the resistance value between the first terminal and the second terminal changes in two stages. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, a semiconductor integrated circuit according to an embodiment will be described with reference to the drawings.

[0008] (First embodiment) FIG. 1 is a diagram illustrating a semiconductor integrated circuit 100 according to a first embodiment. FIG. 2 is a circuit diagram illustrating a portion of the semiconductor integrated circuit 100 according to the first embodiment. The semiconductor integrated circuit 100 illustrated in FIG. 1 is a packaged semiconductor chip. As illustrated in FIG. 1, the semiconductor integrated circuit 100 includes a power supply terminal 10D, a ground terminal 10G, a control terminal 10C, and a switching circuit 20. The power supply terminal 10D, the ground terminal 10G, and the control terminal 10C are exposed to the outside. A power supply voltage VDD is applied to the power supply terminal 10D. A ground GND is connected to the ground terminal 10G. A control voltage VCT is applied to the control terminal 10C. In the first embodiment, the control terminal 10C corresponds to a "first terminal," the ground terminal 10G corresponds to a "second terminal," the power supply terminal 10D corresponds to a "third terminal," and the power supply voltage VDD corresponds to an "input voltage" input from the outside.

[0009] The switching circuit 20 is disposed between a control terminal 10C, which is a first terminal, and a ground terminal 10G, which is a second terminal. As shown in FIG. 2, the switching circuit 20 includes a plurality of transistors 31 to 35 and a plurality of resistance elements 41 to 45. In the first embodiment, the plurality of transistors 31 to 35 are field effect transistors (FETs). The transistors 31, 32, and 34 are P-channel metal-oxide-semiconductor field effect transistors (MOSFETs). The transistors 33 and 35 are N-channel MOSFETs.

[0010] The transistors 31 and 32 are arranged between a power supply terminal 10D to which a power supply voltage VDD is applied and a ground terminal 10G. The transistors 31 and 32 are connected in series. The source terminal of the transistor 31 is connected to the power supply terminal 10D. The drain terminal of the transistor 31 is connected to the source terminal of the transistor 32. The drain terminal of the transistor 32 is connected to the ground GND via a resistive element 45. The gate terminal of the transistor 31 is connected to the drain terminal of the transistor 31. The gate terminal of the transistor 32 is connected to the drain terminal of the transistor 32. As a result, the transistors 31 and 32 are each diode-connected. In the first embodiment, the transistors 31 and 32 correspond to the "first transistor."

[0011] In the circuits disclosed herein, "another element is disposed between a certain element and another element" means that the other element is disposed on the circuit between the certain element and the other element, leading from one to the other.

[0012] The transistors 33, 34, and 35 are arranged between the control terminal 10C and the ground terminal 10G. The drain terminal of the transistor 33 is connected to the control terminal 10C via a resistive element 42. The source terminal of the transistor 33 is connected to the ground GND. The gate terminal of the transistor 33 is connected to the gate terminal of the transistor 31. The source terminal of the transistor 34 is connected to the control terminal 10C. The drain terminal of the transistor 34 is connected to the ground GND via a resistive element 43. The gate terminal of the transistor 34 is connected to the drain terminal of the transistor 33. The drain terminal of the transistor 35 is connected to the control terminal 10C via a resistive element 44. The source terminal of the transistor 35 is connected to the ground GND. The gate terminal of the transistor 35 is connected to the gate terminal of the transistor 32. In the first embodiment, the transistors 33, 34, and 35 correspond to the "second transistor."

[0013] The absolute values ​​of the threshold voltages of the transistors 31 to 35 are the same. However, the absolute values ​​of the threshold voltages of the transistors 31 to 35 may be different from one another. The on-resistance values ​​of the transistors 33, 34, and 35 are sufficiently smaller than the resistance values ​​of the resistive elements 42, 43, and 44. The on-resistance values ​​of the transistors 33, 34, and 35 are, for example, one-hundredth or less of the resistance values ​​of the resistive elements 42, 43, and 44. However, the on-resistance values ​​of the transistors 33, 34, and 35 are not particularly limited.

[0014] One end of the resistor element 41 is connected to the control terminal 10C. The other end of the resistor element 41 is connected to the ground GND. In the first embodiment, the resistor element 41 is a resistor element connected between the control terminal 10C, which is a first terminal, and the ground terminal 10G, which is a second terminal, without a transistor therebetween.

[0015] The resistive elements 42, 43, and 44 are connected in series with the transistors 33, 34, and 35, respectively, between the control terminal 10C and the ground terminal 10G. The resistive element 42 is connected in series with the transistor 33. The resistive element 43 is connected in series with the transistor 34. The resistive element 44 is connected in series with the transistor 35. One end of the resistive element 42 is connected to the control terminal 10C. The other end of the resistive element 42 is connected to the drain terminal of the transistor 33 and the gate terminal of the transistor 34. One end of the resistive element 43 is connected to the drain terminal of the transistor 34. The other end of the resistive element 43 is connected to ground GND. One end of the resistive element 44 is connected to the control terminal 10C. The other end of the resistive element 44 is connected to the drain terminal of the transistor 35. One end of the resistive element 45 is connected to the drain terminal of the transistor 32. The other end of the resistive element 45 is connected to ground GND.

[0016] Resistance elements 41, 42, 43, and 44 are resistance elements that can function as resistance between a control terminal 10C, which is a first terminal, and a ground terminal 10G, which is a second terminal. In the first embodiment, a change in the power supply voltage VDD, which is an input voltage, switches the state of the switching circuit 20, and changes the combination of resistance elements 41 to 44 that function as resistance between the control terminal 10C and the ground terminal 10G. As a result, a change in the power supply voltage VDD input from the outside changes the resistance value CR1 between the control terminal 10C and the ground terminal 10G.

[0017] 3 is a graph showing an example of changes in resistance CR1 between control terminal 10C and ground terminal 10G. In FIG. 3, the horizontal axis represents power supply voltage VDD, and the vertical axis represents resistance CR1 between control terminal 10C and ground terminal 10G. In FIGS. 2 and 3, R1 represents the resistance of resistive element 41, R2 represents the resistance of resistive element 42, R3 represents the resistance of resistive element 43, and R4 represents the resistance of resistive element 44. The resistances R1 to R4 of resistive elements 41 to 44 may be the same or different from one another. In the case of FIG. 3, the control voltage VCT applied to control terminal 10C is a constant voltage equal to or greater than the absolute value of the threshold voltage of transistor 34.

[0018] 3, when the power supply voltage VDD is equal to or higher than 0 V and lower than a voltage value V1, the resistance value CR1 becomes equal to the resistance value R1 of the resistive element 41. The voltage value V1 is the voltage value when the transistor 31 is in the ON state. The voltage value V1 is equal to the threshold voltage of the transistor 31, for example.

[0019] When the power supply voltage VDD is equal to or greater than the voltage value V1 but lower than the voltage value V2, the resistance value CR1 is equal to the combined resistance value R1 / / R2 / / R3 of the parallel-connected resistance elements 41, 42, and 43. The voltage value V2 is higher than the voltage value V1. The voltage value V2 is the voltage value when both transistors 31 and 32 are in the ON state. The absolute value of the voltage value V2 is equal to, for example, the sum of the absolute value of the threshold voltage of transistor 31 and the absolute value of the threshold voltage of transistor 32. In the first embodiment, the absolute value of the threshold voltage of transistor 31 and the absolute value of the threshold voltage of transistor 32 are equal, so the voltage value V2 is, for example, twice the voltage value V1. The combined resistance value R1 / / R2 / / R3 is lower than the resistance value R1.

[0020] When the power supply voltage VDD is equal to or greater than the voltage value V2, the resistance value CR1 is the combined resistance value R1 / / R2 / / R3 / / R4 of the parallel-connected resistance elements 41, 42, 43, and 44. The combined resistance value R1 / / R2 / / R3 / / R4 is lower than the combined resistance value R1 / / R2 / / R3.

[0021] Even if the power supply voltage VDD becomes higher than the voltage value V2, the resistance value CR1 does not change. That is, in the first embodiment, the range in which the resistance value CR1 changes is the range in which the power supply voltage VDD is equal to or lower than the voltage value V2. The voltage value V2 is lower than the voltage value Vd of the power supply voltage VDD input to the semiconductor integrated circuit 100 when the semiconductor integrated circuit 100 is driven. That is, in the first embodiment, the range of the power supply voltage VDD in which the resistance value CR1 between the control terminal 10C and the ground terminal 10G changes is lower than the voltage value Vd of the power supply voltage VDD input during driving.

[0022] As described above, in the first embodiment, the resistance value CR1 between the control terminal 10C and the ground terminal 10G can be changed among three different resistance values ​​by changing the power supply voltage VDD.

[0023] In the first embodiment, when a voltage value equal to or greater than 0V and lower than voltage value V1 corresponds to a "first voltage value," a voltage value equal to or greater than voltage value V1 and lower than voltage value V2, and a voltage value equal to or greater than voltage value V2 correspond to a "second voltage value" higher than the first voltage value. In this case, the resistance value CR1 (resistance value R1) when the power supply voltage VDD is equal to or greater than 0V and lower than voltage value V1 corresponds to a "first resistance value." In this case, the resistance value CR1 (resistance values ​​R1 / / R2 / / R3) when the power supply voltage VDD is equal to or greater than voltage value V1 and lower than voltage value V2, and the resistance value CR1 (resistance values ​​R1 / / R2 / / R3 / / R4) when the power supply voltage VDD is equal to or greater than voltage value V2 correspond to a "second resistance value" lower than the first resistance value.

[0024] When a voltage value equal to or greater than voltage V1 but lower than voltage V2 corresponds to a "first voltage value," a voltage value equal to or greater than voltage V2 corresponds to a "second voltage value" higher than the first voltage value. In this case, the resistance value CR1 (resistance values ​​R1 / / R2 / / R3) when the power supply voltage VDD is equal to or greater than voltage V1 but lower than voltage V2 corresponds to a "first resistance value." In this case, the resistance value CR1 (resistance values ​​R1 / / R2 / / R3 / / R4) when the power supply voltage VDD is equal to or greater than voltage V2 corresponds to a "second resistance value" lower than the first resistance value.

[0025] Next, we will explain how the state of the switching circuit 20 changes when the resistance value CR1 is switched. In the switching circuit 20 shown in FIG. 2, when the power supply voltage VDD is lower than the voltage value V1, the transistors 31 and 32 connected in series between the power supply terminal 10D and the ground terminal 10G are both in the OFF state. In this case, the transistor 33, whose gate terminal is connected to the gate terminal of the transistor 31, and the transistor 35, whose gate terminal is connected to the gate terminal of the transistor 32, are also in the OFF state. When the transistor 33 is in the OFF state, the voltage of the drain terminal of the transistor 33 is the control voltage VCT applied to the control terminal 10C. Therefore, the voltage of the gate terminal of the transistor 34, which is connected to the drain terminal of the transistor 33, is also the control voltage VCT. Therefore, the voltages applied to the gate terminal and source terminal of the transistor 34 are the same value, and the transistor 34 is in the OFF state. As a result, when the power supply voltage VDD is lower than the voltage value V1, all of the transistors 31 to 35 are in the OFF state. As a result, transistor 33, which is arranged between resistive element 42 and ground GND, transistor 34, which is arranged between control terminal 10C and resistive element 43, and transistor 35, which is arranged between resistive element 44 and ground GND, are all in a high impedance state. This opens the connection between control terminal 10C and ground GND via resistive elements 42, 43, and 44. Therefore, only resistive element 41 is connected between control terminal 10C and ground terminal 10G in a state where it functions as a resistor, and resistance value CR1 between control terminal 10C and ground terminal 10G becomes resistance value R1.

[0026] In the switching circuit 20 shown in FIG. 2, when the power supply voltage VDD is equal to or greater than V1 but lower than V2, a voltage equal to or greater than the threshold voltage required to turn on the transistor 31 is applied to the source terminal of the transistor 31. In this case, charge flows from the source terminal to the drain terminal of the transistor 31, increasing the voltages at the drain and gate terminals of the transistor 31. When the voltage at the gate terminal of the transistor 31 exceeds V1, the voltage at the gate terminal of the transistor 33 also exceeds V1, turning the transistor 33 on. When the voltage at the gate terminal of the transistor 31 exceeds V1, the voltage at the drain terminal of the transistor 31 also exceeds V1, so the voltage at the source terminal of the transistor 32 also exceeds V1, turning the transistor 32 on. However, when the power supply voltage VDD is lower than V2, charge flows from the source terminal to the drain terminal of the transistor 32, causing the voltage at the source terminal of the transistor 32 to drop immediately, turning the transistor 32 off. For transistor 32 to be in the ON state, even if a current flows through transistor 32 and the voltage at the source terminal of transistor 32 drops, the dropped source terminal voltage must be greater than the voltages at the drain terminal and gate terminal of transistor 32 by at least the absolute value of the threshold voltage of transistor 32. Therefore, until the power supply voltage VDD reaches voltage value V2, which is the sum of the absolute value of the threshold voltage of transistor 31 and the absolute value of the threshold voltage of transistor 32, the voltages at the gate terminals of transistors 31 and 33 will be equal to or greater than voltage value V1, which is sufficient to turn transistor 33 ON, while transistor 32 will be in the OFF state.

[0027] When transistor 33 is turned on, control terminal 10C is connected to ground terminal 10G via resistor 42. Because the on-resistance of transistor 33 is sufficiently smaller than the resistance R2 of resistor 42, the voltage at the drain terminal of transistor 33 is approximately equal to ground GND. This causes the voltage at the gate terminal of transistor 34, which is connected to the drain terminal of transistor 33, to be approximately equal to ground GND. Because a control voltage VCT greater than or equal to the absolute value of the threshold voltage of transistor 34 is applied to the source terminal of transistor 34, transistor 34 is turned on. This causes control terminal 10C to be connected to ground terminal 10G via resistor 43. Therefore, when power supply voltage VDD is greater than or equal to voltage V1 but less than voltage V2, multiple resistors 41, 42, and 43 are connected in parallel between control terminal 10C and ground terminal 10G, functioning as resistors. Therefore, the resistance value CR1 between the control terminal 10C and the ground terminal 10G is the combined resistance value R1 / / R2 / / R3 of the resistance values ​​R1, R2, and R3 of the resistance elements 41, 42, and 43 connected in parallel.

[0028] In the switching circuit 20 shown in FIG. 2, when the power supply voltage VDD is equal to or greater than the voltage value V2, both transistors 31 and 32 are turned on. When transistor 32 is turned on and charge flows from the source terminal to the drain terminal of transistor 32, the voltages at the drain terminal and gate terminal of transistor 32 increase. When the voltage at the gate terminal of transistor 32 exceeds the absolute value of the threshold voltage, transistor 35, whose gate terminal is connected to the gate terminal of transistor 32, is turned on. When transistor 35 is turned on, the control terminal 10C is connected to the ground terminal 10G via the resistive element 44. Therefore, when the power supply voltage VDD is equal to or greater than the voltage value V2, multiple resistive elements 41, 42, 43, and 44 are connected in parallel between the control terminal 10C and the ground terminal 10G, functioning as resistors. Therefore, the resistance value CR1 between the control terminal 10C and the ground terminal 10G is the combined resistance value R1 / / R2 / / R3 / / R4 of the resistance values ​​R1, R2, R3, and R4 of the resistance elements 41, 42, 43, and 44 connected in parallel.

[0029] As described above, in the first embodiment, a change in the power supply voltage VDD switches the state of the switching circuit 20, changing the combination of the resistive elements functioning as a resistor between the control terminal 10C and the ground terminal 10G. Specifically, when the power supply voltage VDD is equal to or greater than 0 V and lower than a voltage value V1, the resistive element functioning as a resistor between the control terminal 10C and the ground terminal 10G is the resistive element 41. When the power supply voltage VDD is equal to or greater than a voltage value V1 and lower than a voltage value V2, the resistive elements functioning as a resistor between the control terminal 10C and the ground terminal 10G are the resistive elements 41, 42, 43, and 44. When the power supply voltage VDD is equal to or greater than a voltage value V2, the resistive elements functioning as a resistor between the control terminal 10C and the ground terminal 10G are the resistive elements 41, 42, 43, and 44.

[0030] According to the first embodiment, the semiconductor integrated circuit 100 includes a control terminal 10C (first terminal) and a ground terminal 10G (second terminal). A change in the power supply voltage VDD (input voltage) input from the outside changes the resistance CR1 between the control terminal 10C and the ground terminal 10G. Therefore, by changing the power supply voltage VDD input to the semiconductor integrated circuit 100 from the outside, the value of the current flowing between the control terminal 10C and the ground terminal 10G can be changed. This allows the characteristics of the current output when the power supply voltage VDD is applied to the semiconductor integrated circuit 100 from the outside to be different from those of other semiconductor integrated circuits, thereby differentiating the characteristics of the semiconductor integrated circuit 100. Therefore, by detecting the value of the current flowing between the control terminal 10C and the ground terminal 10G with respect to the power supply voltage VDD, it is possible to easily identify the semiconductor integrated circuit 100. For example, the characteristics of the change in the resistance CR1 with respect to the power supply voltage VDD can be made different for each of multiple types of semiconductor integrated circuits 100 that are to be identified from the outside. As a result, by inputting a predetermined value of power supply voltage VDD to each of multiple types of semiconductor integrated circuits 100, it is possible to vary the value of the current flowing between the control terminal 10C and the ground terminal 10G of each type of semiconductor integrated circuit 100. Therefore, by knowing in advance the relationship between the power supply voltage VDD input to each type of semiconductor integrated circuit 100 and the current value output, it is possible to easily identify the type of semiconductor integrated circuit 100 from the output current value. In this way, in the first embodiment, by imparting to the semiconductor integrated circuit 100 a characteristic in which the resistance value CR1 between the control terminal 10C and the ground terminal 10G changes, it is possible to provide differences in the characteristics of the semiconductor integrated circuit 100.

[0031] For example, as shown by the two-dot chain line in FIG. 3 , if there is a semiconductor integrated circuit of the comparative example in which the resistance value CR1 is constant regardless of the value of the power supply voltage VDD, even if a power supply voltage VDD lower than the voltage value V1 is input to the semiconductor integrated circuit of the comparative example, the resistance value CR1 will be the same low value as the combined resistance value R1 / / R2 / / R3 / / R4. On the other hand, in the semiconductor integrated circuit 100 of the first embodiment, when a power supply voltage VDD lower than the voltage value V1 is input, the resistance value CR1 becomes the resistance value R1 higher than the combined resistance value R1 / / R2 / / R3 / / R4. Therefore, when a power supply voltage VDD lower than the voltage value V1 is applied to both the semiconductor integrated circuit 100 of the first embodiment and the semiconductor integrated circuit of the comparative example, the value of the current flowing between the control terminal 10C and the ground terminal 10G in the semiconductor integrated circuit 100 of the first embodiment becomes smaller than that in the semiconductor integrated circuit of the comparative example. This makes it easy to distinguish that the semiconductor integrated circuit 100 of the first embodiment has a smaller value of current flowing between the control terminal 10C and the ground terminal 10G, and the semiconductor integrated circuit of the comparative example has a larger value of current flowing between the control terminal 10C and the ground terminal 10G.

[0032] According to the first embodiment, the range of the power supply voltage VDD (input voltage) in which the resistance value CR1 between the control terminal 10C (first terminal) and the ground terminal 10G (second terminal) changes is lower than the voltage value Vd of the power supply voltage VDD input during operation. Therefore, when the semiconductor integrated circuit 100 is operated, it is possible to suppress changes in the resistance value CR1 between the control terminal 10C and the ground terminal 10G. Therefore, it is possible to suppress the change in the resistance value CR1 from affecting the operation of the semiconductor integrated circuit 100.

[0033] According to the first embodiment, when the power supply voltage VDD (input voltage) is equal to or greater than 0 V and has a first voltage value lower than the voltage value V1, the resistance value CR1 between the control terminal 10C (first terminal) and the ground terminal 10G (second terminal) becomes equal to the resistance value R1 (first resistance value). When the power supply voltage VDD is equal to or greater than the first voltage, that is, when the power supply voltage VDD is equal to or greater than the voltage value V1 and lower than the voltage value V2, the resistance value CR1 between the control terminal 10C and the ground terminal 10G becomes equal to the combined resistance value R1 / / R2 / / R3 (second resistance value) lower than the resistance value R1. Therefore, when the power supply voltage VDD is low, the resistance value CR1 can be increased. This allows the semiconductor integrated circuit 100 to be identified without increasing the power supply voltage VDD.

[0034] According to the first embodiment, the resistance value CR1 between the control terminal 10C (first terminal) and the ground terminal 10G (second terminal) can be changed among three different resistance values ​​by changing the power supply voltage VDD (input voltage). Therefore, by adjusting the resistance values ​​of the resistive elements 41 to 44 to adjust the three resistance values ​​CR1, it is possible to provide more differences in the characteristics of the semiconductor integrated circuit 100. Therefore, it is easier to distinguish the semiconductor integrated circuits 100.

[0035] According to the first embodiment, the semiconductor integrated circuit 100 includes a switching circuit 20 disposed between a control terminal 10C and a ground terminal 10G. The switching circuit 20 includes a plurality of transistors and a plurality of resistive elements. As the power supply voltage VDD (input voltage) changes, the state of the switching circuit 20 is switched, and the combination of resistive elements functioning as a resistor between the control terminal 10C and the ground terminal 10G changes. Therefore, the resistance value CR1 between the control terminal 10C and the ground terminal 10G can be easily changed according to the magnitude of the power supply voltage VDD.

[0036] According to the first embodiment, the multiple transistors included in the switching circuit 20 include transistors 31 and 32 (first transistors) arranged between a power supply terminal 10D to which a power supply voltage VDD (input voltage) is applied and a ground terminal 10G. The transistors 31 and 32 are diode-connected. Therefore, the ON / OFF states of the transistors 31 and 32 can be switched depending on the magnitude of the power supply voltage VDD applied to the power supply terminal 10D. This makes it possible to easily switch the state of the switching circuit 20 depending on the magnitude of the power supply voltage VDD.

[0037] According to the first embodiment, the multiple transistors included in the switching circuit 20 include multiple diode-connected transistors 31 and 32 (first transistors) disposed between the power supply terminal 10D and the ground terminal 10G. The multiple transistors 31 and 32 are connected in series. Therefore, as described above, the states of the multiple transistors 31 and 32 can be switched sequentially as the power supply voltage VDD increases. This allows the state of the switching circuit 20 to be switched stepwise multiple times, and the resistance value CR1 between the control terminal 10C and the ground terminal 10G can be changed in three or more steps. This allows for more differentiation in the characteristics of the semiconductor integrated circuit 100.

[0038] According to the first embodiment, the multiple resistive elements provided in the switching circuit 20 include a resistive element 41 connected between the control terminal 10C and the ground terminal 10G without a transistor. Therefore, the resistive element 41 always functions as a resistor between the control terminal 10C and the ground terminal 10G. This allows the control terminal 10C to be connected to the ground GND regardless of the value of the power supply voltage VDD.

[0039] According to the first embodiment, the multiple transistors included in the switching circuit 20 include transistors 33, 34, and 35 (second transistors) arranged between the control terminal 10C and the ground terminal 10G. The multiple resistive elements included in the switching circuit 20 include resistive elements 42, 43, and 44 connected in series with the transistors 33, 34, and 35 between the control terminal 10C and the ground terminal 10G. Therefore, by switching the states of the transistors 33, 34, and 35 between the ON state and the OFF state, the resistive elements 42, 43, and 44 are switched between a state in which they function as resistors between the control terminal 10C and the ground terminal 10G and a state in which they do not function as resistors between the control terminal 10C and the ground terminal 10G, i.e., an open state. This makes it possible to easily change the resistance value CR1 between the control terminal 10C and the ground terminal 10G.

[0040] According to the first embodiment, the semiconductor integrated circuit 100 includes a power supply terminal 10D as a third terminal. The power supply terminal 10D is a terminal to which a power supply voltage VDD, which is an input voltage, is applied. Therefore, the terminal to which the power supply voltage VDD is input can be a terminal separate from the control terminal 10C and the ground terminal 10G. As a result, by keeping the control voltage VCT applied to the control terminal 10C constant, the value of the current flowing between the control terminal 10C and the ground terminal 10G can be kept constant regardless of the power supply voltage VDD, as long as the resistance value CR1 between the control terminal 10C and the ground terminal 10G is the same. Therefore, by detecting the value of the current flowing between the control terminal 10C and the ground terminal 10G, the semiconductor integrated circuit 100 can be more easily identified.

[0041] (Second embodiment) The second embodiment differs from the first embodiment in the configuration of the switching circuit 220. In the following description, the same components as those in the above-described embodiments may be denoted by the same reference numerals as appropriate, and the description thereof may be omitted.

[0042] Fig. 4 is a circuit diagram showing a semiconductor integrated circuit 200 according to the second embodiment. As shown in Fig. 4, the semiconductor integrated circuit 200 includes a power supply terminal 210D, a control terminal 210C, and a ground terminal 210G. In the second embodiment, the power supply terminal 210D corresponds to the "first terminal," and the control terminal 210C corresponds to the "second terminal."

[0043] The switching circuit 220 includes a plurality of transistors 31, 32, 233, 234, 235, and 236, and a plurality of resistor elements 241, 242, 243, 244, 245, and 246. The transistor 233 is similar to the transistor 33 of the first embodiment, except that a drain terminal of the transistor 233 is connected to the power supply terminal 210D via a resistor element 244. The transistor 235 is similar to the transistor 35 of the first embodiment, except that a drain terminal of the transistor 235 is connected to the power supply terminal 210D via a resistor element 246.

[0044] The transistors 234 and 236 are arranged between the power supply terminal 210D and the control terminal 210C. In the second embodiment, the transistors 234 and 236 correspond to the "second transistor." The transistors 234 and 236 are field-effect transistors. More specifically, the transistors 234 and 236 are P-channel MOSFETs. The source terminal of the transistor 234 is connected to the power supply terminal 210D. The drain terminal of the transistor 234 is connected to the control terminal 210C via a resistor 242. The gate terminal of the transistor 234 is connected to the drain terminal of the transistor 233. The source terminal of the transistor 236 is connected to the power supply terminal 210D. The drain terminal of the transistor 236 is connected to the control terminal 210C via a resistor 243.

[0045] The absolute values ​​of the threshold voltages of the transistors 31 to 236 are the same. However, the absolute values ​​of the threshold voltages of the transistors 31 to 236 may be different from one another. The on-resistance values ​​of the transistors 234 and 236 are sufficiently smaller than the resistance values ​​of the resistive elements 242 and 243. The on-resistance values ​​of the transistors 234 and 236 are, for example, one-hundredth or less of the resistance values ​​of the resistive elements 242 and 243. However, the on-resistance values ​​of the transistors 234 and 236 are not particularly limited.

[0046] The resistive elements 241, 242, and 243 are disposed between the power supply terminal 210D and the control terminal 210C. One end of the resistive element 241 is connected to the power supply terminal 210D. The other end of the resistive element 241 is connected to the control terminal 210C. The resistive element 241 is a resistive element connected between the power supply terminal 210D, which is a first terminal, and the control terminal 210C, which is a second terminal, without a transistor interposed therebetween. One end of the resistive element 242 is connected to the drain terminal of the transistor 234. The other end of the resistive element 242 is connected to the control terminal 210C. One end of the resistive element 243 is connected to the drain terminal of the transistor 236. The other end of the resistive element 243 is connected to the control terminal 210C. The resistive elements 242 and 243 are resistive elements connected in series with the transistors 234 and 236, respectively, between the power supply terminal 210D and the control terminal 210C.

[0047] The resistive elements 244 and 246 are disposed between the power supply terminal 210D and the ground terminal 10G. One end of the resistive element 244 is connected to the power supply terminal 210D. The other end of the resistive element 244 is connected to the drain terminal of the transistor 233. One end of the resistive element 246 is connected to the power supply terminal 210D. The other end of the resistive element 246 is connected to the drain terminal of the transistor 235.

[0048] In the second embodiment, the resistive elements 241, 242, and 243 are resistive elements that can function as a resistor between the power supply terminal 210D, which is a first terminal, and the control terminal 210C, which is a second terminal. In the second embodiment, the state of the switching circuit 20 is switched by a change in the power supply voltage VDD, which is an input voltage, and the combination of the resistive elements 241 to 243 that function as a resistor between the power supply terminal 210D and the control terminal 210C changes. As a result, a resistance value CR2 between the power supply terminal 210D and the control terminal 210C changes as the power supply voltage VDD input from the outside changes.

[0049] Fig. 5 is a graph showing an example of changes in resistance value CR2 between power supply terminal 210D and control terminal 210C. In Fig. 5, the horizontal axis represents power supply voltage VDD, and the vertical axis represents resistance value CR2 between power supply terminal 210D and control terminal 210C. In Figs. 4 and 5, R1 represents the resistance value of resistive element 241, R2 represents the resistance value of resistive element 242, and R3 represents the resistance value of resistive element 243. In the case of Fig. 5, control voltage VCT applied to control terminal 210C is equal to or lower than power supply voltage VDD applied to power supply terminal 210D.

[0050] As shown in FIG. 5, when the power supply voltage VDD is equal to or greater than 0 V and lower than V1, the resistance value CR2 is equal to the resistance value R1 of the resistor element 241. When the power supply voltage VDD is equal to or greater than V1 and lower than V2, the resistance value CR2 is equal to the combined resistance value R1 / / R2 of the resistor elements 241 and 242 connected in parallel. The combined resistance value R1 / / R2 is lower than the resistance value R1. When the power supply voltage VDD is equal to or greater than V2, the resistance value CR2 is equal to the combined resistance value R1 / / R2 / / R3 of the resistor elements 241, 242, and 243 connected in parallel. The combined resistance value R1 / / R2 / / R3 is lower than the combined resistance value R1 / / R2. Even if the power supply voltage VDD becomes higher than V2, the resistance value CR2 does not change. That is, in the second embodiment, the range in which the resistance value CR2 changes is the range in which the power supply voltage VDD is equal to or lower than V2.

[0051] In the second embodiment, when the resistance value R1 corresponds to the "first resistance value," the combined resistance values ​​R1 / / R2 and R1 / / R2 / / R3 correspond to the "second resistance value." When the combined resistance value R1 / / R2 corresponds to the "first resistance value," the combined resistance value R1 / / R2 / / R3 corresponds to the "second resistance value."

[0052] Next, a description will be given of the change in state of the switching circuit 220 when the resistance value CR2 is switched. In the switching circuit 220 shown in FIG. 4, when the power supply voltage VDD is lower than the voltage value V1, the transistors 31, 32, 233, 234, and 235 are turned off, as in the first embodiment. When the transistor 235 is turned off, the voltage at the drain terminal of the transistor 235 is the power supply voltage VDD applied to the power supply terminal 210D. Therefore, the voltage at the gate terminal of the transistor 236 connected to the drain terminal of the transistor 235 is also the power supply voltage VDD. Therefore, the voltages applied to the gate terminal and source terminal of the transistor 236 are the same value, and the transistor 236 is turned off. As a result, when the power supply voltage VDD is lower than the voltage value V1, all of the transistors 31 to 236 are turned off. Therefore, only resistive element 241 is connected between power supply terminal 210D and control terminal 210C in a state where it functions as a resistor, and resistance value CR2 between power supply terminal 210D and control terminal 210C becomes resistance value R2.

[0053] In the switching circuit 220 shown in FIG. 4, when the power supply voltage VDD is equal to or greater than the voltage value V1 but lower than the voltage value V2, a voltage equal to or greater than the threshold voltage required to turn the transistor 31 ON is applied to the source terminal of the transistor 31. As a result, similar to the first embodiment, the transistors 233 and 234 are turned ON. Meanwhile, the transistors 32, 235, and 236 remain OFF. Therefore, the resistive elements 241 and 242 are connected in parallel between the power supply terminal 210D and the control terminal 210C, functioning as resistors. Therefore, when the power supply voltage VDD is equal to or greater than the voltage value V1 but lower than the voltage value V2, the resistance value CR2 between the power supply terminal 210D and the control terminal 210C is the combined resistance value R1 / / R2 of the resistance values ​​R1 and R2 of the resistive elements 241 and 242 connected in parallel.

[0054] In the switching circuit 220 shown in FIG. 4, when the power supply voltage VDD is equal to or greater than the voltage value V2, the transistor 32 is turned on, as in the first embodiment. This causes the transistors 31, 32, 233, 234, and 235 to be turned on, as in the first embodiment. When the transistor 235 is turned on, the voltage at the drain terminal of the transistor 235 becomes substantially equal to the ground GND. This causes the voltage at the gate terminal of the transistor 236, connected to the drain terminal of the transistor 235, to become substantially equal to the ground GND. Because the power supply voltage VDD is applied to the source terminal of the transistor 236, the transistor 236 is turned on. When the transistor 236 is turned on, the power supply terminal 210D is connected to the control terminal 210C via the resistive element 243. Therefore, when the power supply voltage VDD is equal to or greater than the voltage value V2, the resistive elements 241, 242, and 243 are connected in parallel between the power supply terminal 210D and the control terminal 210C, functioning as resistors. Therefore, the resistance value CR2 between the power supply terminal 210D and the control terminal 210C is the combined resistance value R1 / / R2 / / R3 of the resistance values ​​R1, R2, and R3 of the resistance elements 241, 242, and 243.

[0055] Other configurations and operations of the switching circuit 220 are similar to those of the switching circuit 20 in the first embodiment. Other configurations and operations of the semiconductor integrated circuit 200 are similar to those of the semiconductor integrated circuit 100 in the first embodiment.

[0056] According to the second embodiment, the first terminal, power supply terminal 210D, is a terminal to which power supply voltage VDD is applied as an input voltage. Therefore, the terminal to which the input voltage is applied and one terminal for detecting a current based on a change in resistance value CR2 can be the same terminal. This allows a test to identify the semiconductor integrated circuit 200 using only two terminals. This makes it easier to identify the semiconductor integrated circuit 200.

[0057] (Third embodiment) The third embodiment differs from the first embodiment in the configuration of the switching circuit 320. In the following description, the same components as those in the above-described embodiments may be denoted by the same reference numerals as appropriate, and the description thereof may be omitted.

[0058] FIG. 6 is a circuit diagram showing a semiconductor integrated circuit 300 according to the third embodiment. As shown in FIG. 6, a switching circuit 320 of the semiconductor integrated circuit 300 includes a current source circuit 350. The current source circuit 350 includes a pair of transistors 351 and 352. The pair of transistors 351 and 352 are field-effect transistors. More specifically, the pair of transistors 351 and 352 are P-channel MOSFETs. The pair of transistors 351 and 352 form a current mirror circuit. The source terminals of the transistors 351 and 352 are connected to each other. The source terminals of the transistors 351 and 352 are connected to a power supply terminal 310D. The power supply terminal 310D is similar to the power supply terminal 10D of the first embodiment, except that it is connected to the source terminal of the transistor 31 via the current source circuit 350.

[0059] The drain terminal of the transistor 351 is connected to the ground GND via the resistor element 346. The drain terminal of the transistor 351 is connected to the gate terminal of the transistor 351. The drain terminal of the transistor 352 is connected to the source terminal of the transistor 351. The gate terminal of the transistor 352 is connected to the gate terminal of the transistor 351.

[0060] When the power supply voltage VDD applied to the power supply terminal 310D increases and the transistor 351 turns on, a current Id flows from the power supply terminal 310D to ground GND via the transistor 351. The current Id is expressed as Id = (VDD - Vth) / R6, where Vth is the absolute value of the threshold voltage of the transistor 351. R6 is the resistance of the resistor 346. The pair of transistors 351 and 352 form a current mirror circuit. Therefore, when the current Id flows through the transistor 351, a current proportional to the size ratio between the transistors 351 and 352 also flows through the transistor 352. When a current flows through the transistor 352, the voltage at the source terminal of the transistor 31 increases. This allows a voltage to be applied to the source terminal of the transistor 31 via the current source circuit 350.

[0061] Other configurations and operations of the switching circuit 320 are similar to those of the switching circuit 20 in the first embodiment. Other configurations and operations of the semiconductor integrated circuit 300 are similar to those of the semiconductor integrated circuit 100 in the first embodiment.

[0062] (Fourth embodiment) The fourth embodiment differs from the first embodiment in the configuration of the switching circuit 420. In the following description, the same components as those in the above-described embodiments may be denoted by the same reference numerals as appropriate, and the description thereof may be omitted.

[0063] 7 is a circuit diagram showing a semiconductor integrated circuit 400 of the fourth embodiment. As shown in FIG. 7, a switching circuit 420 of the semiconductor integrated circuit 400 has a plurality of transistors 431 to 437 and a plurality of resistor elements 441 to 446. The plurality of transistors 431 to 437 are field-effect transistors. The plurality of transistors 431, 432, and 433 are P-channel MOSFETs. The plurality of transistors 434, 435, 436, and 437 are N-channel MOSFETs.

[0064] In the fourth embodiment, the multiple transistors 431, 432, and 433 correspond to "first transistors" arranged between the power supply terminal 410D and the ground terminal 10G. The multiple transistors 431, 432, and 433 are each diode-connected. The transistors 431, 432, and 433 are connected in series. The source terminal of the transistor 431 is connected to the power supply terminal 410D. The drain terminal of the transistor 431 is connected to the gate terminal of the transistor 431 and the source terminal of the transistor 432. The drain terminal of the transistor 432 is connected to the gate terminal of the transistor 432 and the source terminal of the transistor 433. The drain terminal of the transistor 433 is connected to the gate terminal of the transistor 433. The drain terminal of the transistor 433 is connected to the ground GND via a resistor 446.

[0065] The transistors 434 and 436 are arranged between the power supply terminal 410D and the ground terminal 10G. The drain terminal of the transistor 434 is connected to the power supply terminal 410D via a resistive element 444. The source terminal of the transistor 434 is connected to the ground GND. The gate terminal of the transistor 434 is connected to the gate terminal of the transistor 432. The drain terminal of the transistor 436 is connected to the power supply terminal 410D via a resistive element 445. The source terminal of the transistor 436 is connected to the ground GND. The gate terminal of the transistor 436 is connected to the gate terminal of the transistor 433.

[0066] In the fourth embodiment, the transistors 435 and 437 correspond to a "second transistor" arranged between the control terminal 410C and the ground terminal 10G. The drain terminal of the transistor 435 is connected to the control terminal 410C via a resistor 441. The source terminal of the transistor 435 is connected to the ground GND. The gate terminal of the transistor 435 is connected to the drain terminal of the transistor 434. The drain terminal of the transistor 437 is connected to the control terminal 410C via resistors 441 and 442. The source terminal of the transistor 437 is connected to the ground GND. The gate terminal of the transistor 437 is connected to the drain terminal of the transistor 436.

[0067] The absolute values ​​of the threshold voltages of the transistors 431 to 437 are the same. However, the absolute values ​​of the threshold voltages of the transistors 431 to 437 may be different from one another. The on-resistance values ​​of the transistors 435 and 437 are sufficiently smaller than the resistance values ​​of the resistive elements 441, 442, and 443. The on-resistance values ​​of the transistors 435 and 437 are, for example, one-hundredth or less of the resistance values ​​of the resistive elements 441, 442, and 443. However, the on-resistance values ​​of the transistors 435 and 437 are not particularly limited.

[0068] Resistance element 441 is connected in series with transistor 435 between control terminal 410C and ground terminal 10G. Resistance elements 441 and 442 are connected in series with transistor 437 between control terminal 410C and ground terminal 10G. Resistance elements 441, 442, and 443 are connected in series between control terminal 410C and ground terminal 10G without a transistor in between.

[0069] One end of the resistor element 441 is connected to the control terminal 410C. The other end of the resistor element 441 is connected to the drain terminal of the transistor 435 and one end of the resistor element 442. The other end of the resistor element 442 is connected to the drain terminal of the transistor 437 and one end of the resistor element 443. The other end of the resistor element 443 is connected to the ground GND.

[0070] Other configurations of the power supply terminal 410D are the same as other configurations of the power supply terminal 10D in the first embodiment. Other configurations of the control terminal 410C are the same as other configurations of the control terminal 10C in the first embodiment. In the fourth embodiment, the power supply terminal 410D corresponds to the "third terminal" and the control terminal 410C corresponds to the "first terminal."

[0071] In the fourth embodiment, the resistive elements 441, 442, and 443 are resistive elements that can function as a resistor between the control terminal 410C, which is a first terminal, and the ground terminal 10G, which is a second terminal. In the fourth embodiment, the state of the switching circuit 420 is switched by a change in the power supply voltage VDD, which is an input voltage, and the combination of the resistive elements 441 to 443 that function as a resistor between the control terminal 410C and the ground terminal 10G changes. As a result, a resistance value CR3 between the control terminal 410C and the ground terminal 10G changes as the power supply voltage VDD input from the outside changes.

[0072] 8 is a graph showing an example of changes in resistance value CR3 between control terminal 410C and ground terminal 10G. In Fig. 8, the horizontal axis represents power supply voltage VDD, and the vertical axis represents resistance value CR3 between control terminal 410C and ground terminal 10G. In Fig. 7 and Fig. 8, R1 represents the resistance value of resistive element 441, R2 represents the resistance value of resistive element 442, and R3 represents the resistance value of resistive element 443.

[0073] As shown in FIG. 8, when the power supply voltage VDD is equal to or greater than 0 V and lower than a voltage value V1, the resistance value CR3 is equal to the combined resistance value R1+R2+R3 of the series-connected resistance elements 441, 442, and 443. The voltage value V1 is equal to, for example, the absolute value of the threshold voltages of the transistors 435 and 437. When the power supply voltage VDD is equal to or greater than a voltage value V1 and lower than a voltage value V2, the resistance value CR3 is equal to the resistance value R1 of the resistance element 441. The resistance value R1 is lower than the combined resistance value R1+R2+R3. The voltage value V2 is higher than the voltage value V1. The voltage value V2 is equal to, for example, the sum of the absolute value of the threshold voltage of the transistor 431 and the absolute value of the threshold voltage of the transistor 432. In the fourth embodiment, the absolute values ​​of the threshold voltages of the transistors are equal to each other, so the voltage value V2 is twice the voltage value V1.

[0074] When the power supply voltage VDD is equal to or greater than the voltage V2 but lower than the voltage V3, the resistance CR3 is the combined resistance R1+R2 of the resistor elements 441 and 442 connected in series. The combined resistance R1+R2 is higher than the resistance R1 but lower than the combined resistance R1+R2+R3. The voltage V3 is higher than the voltage V2. For example, the voltage V3 is equal to the sum of the absolute values ​​of the threshold voltages of the transistors 431, 432, and 433. In the fourth embodiment, the absolute values ​​of the threshold voltages of the transistors are equal to each other, so the voltage V3 is three times the voltage V1.

[0075] When the power supply voltage VDD is equal to or greater than the voltage V3, the resistance value CR3 is equal to the combined resistance value R1+R2+R3 of the series-connected resistor elements 441, 442, and 443. Even if the power supply voltage VDD becomes higher than the voltage V3, the resistance value CR3 does not change. In other words, in the fourth embodiment, the range in which the resistance value CR3 changes is the range in which the power supply voltage VDD is equal to or less than the voltage V3.

[0076] If a voltage value equal to or greater than voltage V1 but lower than voltage V2 corresponds to the "third voltage value," a voltage value equal to or greater than voltage V2 but lower than voltage V3, and a voltage value equal to or greater than voltage V3 correspond to the "fourth voltage value." In this case, the resistance value CR3 (resistance value R1) when the power supply voltage VDD is equal to or greater than voltage V1 but lower than voltage V2 corresponds to the "third resistance value." In this case, the resistance value CR3 (resistance value R1+R2) when the power supply voltage VDD is equal to or greater than voltage V2 but lower than voltage V3, and the resistance value CR3 (resistance value R1+R2+R3) when the power supply voltage VDD is equal to or greater than voltage V3 correspond to the "fourth resistance value," which is higher than the third resistance value.

[0077] When a voltage value equal to or greater than voltage V2 but lower than voltage V3 corresponds to the "third voltage value," a voltage value equal to or greater than voltage V3 corresponds to the "fourth voltage value." In this case, when the power supply voltage VDD is equal to or greater than voltage V2 but lower than voltage V3, the resistance value CR3 (resistance value R1+R2) corresponds to the "third resistance value." In this case, when the power supply voltage VDD is equal to or greater than voltage V3, the resistance value CR3 (resistance value R1+R2+R3) corresponds to the "fourth resistance value" higher than the third resistance value.

[0078] Next, a description will be given of the change in state of the switching circuit 320 when the resistance value CR3 is switched. In the switching circuit 320 shown in Fig. 7, when the power supply voltage VDD is lower than the voltage value V1, the transistors 431, 432, and 433 are turned OFF, as in the first embodiment. In this case, the transistor 434, whose gate terminal is connected to the gate terminal of the transistor 432, and the transistor 436, whose gate terminal is connected to the gate terminal of the transistor 433, are also turned OFF.

[0079] The gate terminals of the transistors 435 and 437 are connected to the power supply terminal 410D via resistor elements 444 and 445, respectively. Therefore, the power supply voltage VDD is applied to the gate terminals of the transistors 435 and 437. However, when the power supply voltage VDD is lower than a voltage value V1, which is equal to the absolute value of the threshold voltages of the transistors 435 and 437, the transistors 435 and 437 are turned off. In this case, three resistor elements 441, 442, and 443 are connected in series between the control terminal 410C and the ground terminal 10G, functioning as resistors. As a result, when the power supply voltage VDD is lower than the voltage value V1, the resistance value CR3 between the control terminal 410C and the ground terminal 10G is the combined resistance value R1+R2+R3.

[0080] When the power supply voltage VDD is equal to or greater than the voltage value V1 but lower than the voltage value V2, a voltage equal to or greater than the threshold voltage of the transistor 431 is applied to the source terminal of the transistor 431. However, a voltage lower than the voltage value V2, which is twice the absolute value of the threshold voltage, cannot turn the transistor 432 ON. Therefore, the transistors 432 and 433 remain OFF. Meanwhile, the power supply voltage VDD applied to the gate terminals of the transistors 435 and 437 is equal to or greater than the absolute value of the threshold voltages of the transistors 435 and 437, so the transistors 435 and 437 are ON. When the transistor 435 is ON, the control terminal 410C and the ground terminal 10G are connected via the resistor element 441 and the transistor 435. When the transistor 437 is ON, the control terminal 410C and the ground terminal 10G are connected via the resistor element 441, the resistor element 442, and the transistor 437. In this case, the current flowing from the control terminal 410C to the ground terminal 10G flows through a path that passes through the resistor element 441 and the transistor 435, which has a lower resistance value than the other paths. Therefore, the resistor element connected between the control terminal 410C and the ground terminal 10G can be considered to be only the resistor element 441. As a result, when the power supply voltage VDD is equal to or greater than the voltage value V1 and lower than the voltage value V2, the resistance value CR3 between the control terminal 410C and the ground terminal 10G becomes the resistance value R1.

[0081] When the power supply voltage VDD is equal to or greater than the voltage value V2 but lower than the voltage value V3, i.e., when the power supply voltage VDD is equal to or greater than two times but lower than three times the absolute value of the threshold voltage, the transistors 431 and 432 are turned on, and the voltages at the drain and gate terminals of the transistor 432 rise. This causes the transistor 434, whose gate terminal is connected to the gate terminal of the transistor 432, to turn on. When the transistor 434 turns on, the voltage at the drain terminal of the transistor 434 becomes approximately equal to the ground potential GND. This causes the transistor 435, whose gate terminal is connected to the drain terminal of the transistor 434, to turn off. On the other hand, when the power supply voltage VDD is equal to or greater than the voltage value V2 but lower than the voltage value V3, the power supply voltage VDD has not reached a voltage value that can turn the transistor 433 on, and the transistor 433 remains off. Therefore, the transistor 436, whose gate terminal is connected to the gate terminal of the transistor 433, also remains off. This causes the transistor 437 to remain on. Therefore, when the power supply voltage VDD is equal to or greater than the voltage value V2 but lower than the voltage value V3, the path from the control terminal 410C to the ground terminal 10G via the resistor element 441 and the transistor 435 becomes high impedance, while the control terminal 410C and the ground terminal 10G are connected via the resistor elements 441, 442 and the transistor 437. Therefore, when the power supply voltage VDD is equal to or greater than the voltage value V2 but lower than the voltage value V3, the resistance value CR3 between the control terminal 410C and the ground terminal 10G becomes the combined resistance value R1+R2 of the two resistor elements 441, 442.

[0082] When the power supply voltage VDD is equal to or greater than the voltage value V3, i.e., when the power supply voltage VDD is equal to or greater than three times the absolute value of the threshold voltage, transistors 431, 432, and 433 are turned on. This also turns on transistor 434, whose gate terminal is connected to the gate terminal of transistor 432, and transistor 436, whose gate terminal is connected to the gate terminal of transistor 433. When transistor 436 is turned on, the voltage of the drain terminal of transistor 436 becomes approximately equal to the ground potential. This causes transistor 437, whose gate terminal is connected to the drain terminal of transistor 436, to be turned off. Therefore, both the path from control terminal 410C to ground terminal 10G via resistor 441 and transistor 435 and the path from control terminal 410C to ground terminal 10G via resistors 441, 442, and transistor 437 become high impedance. Therefore, current flows through the path from control terminal 410C to ground terminal 10G via resistors 441, 442, and 443. Therefore, when the voltage value is equal to or higher than V3, the resistance value CR3 between the control terminal 410C and the ground terminal 10G is the combined resistance value R1+R2+R3 of the resistance elements 441, 442, and 443.

[0083] Other configurations and operations of the switching circuit 420 are similar to those of the switching circuit 20 in the first embodiment. Other configurations and operations of the semiconductor integrated circuit 400 are similar to those of the semiconductor integrated circuit 100 in the first embodiment.

[0084] According to the fourth embodiment, when the power supply voltage VDD (input voltage) is equal to or greater than the voltage value V1 and is equal to a third voltage value lower than the voltage value V2, the resistance value CR3 between the control terminal 410C and the ground terminal 10G becomes a third resistance value (resistance value R1). When the power supply voltage VDD is equal to or greater than the voltage value V2 and is equal to a fourth voltage value lower than the voltage value V3, the resistance value CR3 between the control terminal 410C and the ground terminal 10G becomes a fourth resistance value (resistance value R1+R2) higher than the third resistance value. Therefore, when the power supply voltage VDD increases, the resistance value CR3 between the control terminal 410C and the ground terminal 10G can be increased. Even in this case, by appropriately setting the value of each resistance element, the value of the current flowing between the control terminal 410C and the ground terminal 10G when a predetermined power supply voltage VDD is applied to the semiconductor integrated circuit 400 can be adjusted. This allows the semiconductor integrated circuit 400 to have characteristics different from other semiconductor integrated circuits. Therefore, similar to the above-described embodiments, the semiconductor integrated circuit 400 can be easily identified. Furthermore, when the power supply voltage VDD increases, the resistance CR3 between the control terminal 410C and the ground terminal 10G increases. For example, when the control voltage VCT applied to the control terminal 410C increases with an increase in the power supply voltage VDD, the value of the current flowing between the control terminal 410C and the ground terminal 10G is less likely to change. Therefore, by appropriately designing the change in the resistance CR3 in response to changes in the power supply voltage VDD, a constant current circuit can be obtained with a simple structure. For example, in a configuration in which the resistance between the power supply terminal 410D and another terminal increases when the power supply voltage VDD applied to the power supply terminal 410D increases, the value of the current flowing between the power supply terminal 410D and another terminal is less likely to change even when the power supply voltage VDD changes, as long as the voltage of the other terminal remains constant.

[0085] According to at least one of the embodiments described above, the semiconductor integrated circuit of the embodiment has a first terminal and a second terminal. The resistance value between the first terminal and the second terminal changes as the input voltage applied from the outside changes. This makes it easy to identify the semiconductor integrated circuit.

[0086] In the above-described embodiments, the resistance between the first and second terminals varies in three stages in response to changes in the input voltage. However, this is not limiting. The resistance between the first and second terminals may also vary in two stages in response to changes in the input voltage. FIG. 9 is a graph showing an example of a modified example in which the resistance CR4 between the first and second terminals varies in two stages. As shown in FIG. 9, when the power supply voltage VDD is equal to or greater than 0 V and lower than the voltage V1, the resistance CR4 is equal to the resistance R1. When the power supply voltage VDD is equal to or greater than the voltage V1, the resistance CR4 is equal to the combined resistance R1 / / R2 / / R3. When the power supply voltage VDD is greater than the voltage V1, the resistance CR4 does not change. A semiconductor integrated circuit in which the resistance CR4 varies as shown in FIG. 9 can be realized, for example, by removing transistor 32 from the semiconductor integrated circuit 100 of the first embodiment, connecting the drain terminal of transistor 31 to one end of resistor 45, and removing the path from the control terminal 10C to the ground terminal 10G via resistor 44 and transistor 35. In this case, the resistance value CR4 is the resistance value between the control terminal 10C and the ground terminal 10G.

[0087] The resistance between the first terminal and the second terminal may be variable among three or more different resistance values ​​as the input voltage changes. The resistance between the first terminal and the second terminal may vary in any manner with respect to the input voltage. The resistance between the first terminal and the second terminal may vary continuously with respect to the input voltage. The input voltage may be any voltage, and may be a voltage other than the power supply voltage. The input voltage may be the control voltage VCT in the above-described embodiments. The value of the input voltage at which the resistance between the first terminal and the second terminal changes is not particularly limited. For example, the voltage values ​​V1 and V2 described in the above-described embodiments may be different values ​​in each embodiment. The first terminal and the second terminal may be any terminal. The first terminal and the second terminal may be terminals other than a power supply terminal, a ground terminal, or a control terminal. As long as the resistance between the first terminal and the second terminal changes with respect to the input voltage, the circuit configuration of the semiconductor integrated circuit is not particularly limited and may be any circuit configuration.

[0088] When the switching circuit of the semiconductor integrated circuit has a plurality of transistors, the types of the transistors are not particularly limited. The plurality of transistors in the switching circuit may be, for example, bipolar transistors. When the switching circuit has a plurality of resistor elements, the resistance values ​​of the resistor elements are not particularly limited.

[0089] The characteristic of a semiconductor integrated circuit, in which the resistance value between the first terminal and the second terminal changes as the input voltage changes, may be used for purposes other than identifying the semiconductor integrated circuit described above. For example, the resistance value between the first terminal and the second terminal may change depending on the input voltage, and the function of the semiconductor integrated circuit may be switched for each changed resistance value. Furthermore, as described in the fourth embodiment, the change in the characteristic may be utilized to configure a circuit having a specific function, such as a constant current circuit.

[0090] The input circuit and the semiconductor device according to the embodiments include the following additional features. (Appendix 1) A first terminal; A second terminal; Equipped with A semiconductor integrated circuit in which a resistance value between the first terminal and the second terminal changes in response to a change in an externally applied input voltage. (Appendix 2) 2. The semiconductor integrated circuit according to claim 1, wherein the range of the input voltage in which the resistance value between the first terminal and the second terminal changes is lower than the voltage value of the input voltage input during operation. (Appendix 3) When the input voltage has a first voltage value, a resistance value between the first terminal and the second terminal becomes a first resistance value; 3. The semiconductor integrated circuit according to claim 1, wherein, when the input voltage is a second voltage value higher than the first voltage value, a resistance value between the first terminal and the second terminal becomes a second resistance value lower than the first resistance value. (Appendix 4) when the input voltage has a third voltage value, a resistance value between the first terminal and the second terminal is a third resistance value; 4. The semiconductor integrated circuit according to claim 1, wherein, when the input voltage is a fourth voltage value higher than the third voltage value, a resistance value between the first terminal and the second terminal becomes a fourth resistance value higher than the third resistance value. (Appendix 5) 5. The semiconductor integrated circuit according to claim 1, wherein a resistance value between the first terminal and the second terminal can be changed among three or more different resistance values ​​by changing the input voltage. (Appendix 6) a switching circuit disposed between the first terminal and the second terminal; the switching circuit includes a plurality of transistors and a plurality of resistor elements; 6. The semiconductor integrated circuit according to claim 1, wherein a change in the input voltage switches a state of the switching circuit, and a combination of the resistive elements functioning as a resistor between the first terminal and the second terminal changes. (Appendix 7) the plurality of transistors includes a first transistor disposed between a terminal to which the input voltage is applied and the second terminal; 7. The semiconductor integrated circuit according to claim 6, wherein the first transistor is diode-connected. (Appendix 8) the plurality of transistors includes a plurality of the first transistors, 8. The semiconductor integrated circuit according to claim 7, wherein the plurality of first transistors are connected in series. (Appendix 9) 9. The semiconductor integrated circuit according to claim 6, wherein the plurality of resistive elements include a resistive element connected between the first terminal and the second terminal without a transistor therebetween. (Appendix 10) the plurality of transistors includes a second transistor disposed between the first terminal and the second terminal; 10. The semiconductor integrated circuit according to claim 6, wherein the plurality of resistive elements include a resistive element connected in series with the second transistor between the first terminal and the second terminal. (Appendix 11) A third terminal is provided. 11. The semiconductor integrated circuit according to claim 1, wherein the third terminal is a terminal to which the input voltage is applied. (Appendix 12) 11. The semiconductor integrated circuit according to claim 1, wherein the first terminal is a terminal to which the input voltage is applied.

[0091] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0092] 10C, 410C...Control terminal (first terminal), 10D, 310D, 410D...Power terminal (third terminal), 10G...Ground terminal (second terminal), 20, 220, 320, 420...Switching circuit, 31, 32, 431...Transistor (first transistor), 33, 34, 35, 233, 234, 235, 236, 351, 352, 431, 432, 433, 434, 435, 436, 4 37...transistor, 41, 42, 43, 44, 45, 241, 242, 243, 244, 246, 346, 441, 442, 443, 444, 445, 446...resistance elements, 100, 200, 300, 400...semiconductor integrated circuit, 210C...control terminal (second terminal), 210D...power supply terminal (first terminal), CR1, CR2, CR3, CR4...resistance value, VDD...power supply voltage (input voltage)

Claims

1. A first terminal; A second terminal; Equipped with A semiconductor integrated circuit in which a resistance value between the first terminal and the second terminal changes in response to a change in an externally applied input voltage.

2. 2. The semiconductor integrated circuit according to claim 1, wherein the range of the input voltage in which the resistance value between the first terminal and the second terminal changes is lower than the voltage value of the input voltage input during driving.

3. When the input voltage has a first voltage value, a resistance value between the first terminal and the second terminal becomes a first resistance value; 2. The semiconductor integrated circuit according to claim 1, wherein when the input voltage is a second voltage value higher than the first voltage value, a resistance value between the first terminal and the second terminal becomes a second resistance value lower than the first resistance value.

4. when the input voltage has a third voltage value, a resistance value between the first terminal and the second terminal is a third resistance value; 2. The semiconductor integrated circuit according to claim 1, wherein when the input voltage is a fourth voltage value higher than the third voltage value, a resistance value between the first terminal and the second terminal becomes a fourth resistance value higher than the third resistance value.

5. 2. The semiconductor integrated circuit according to claim 1, wherein the resistance value between the first terminal and the second terminal can be changed among three or more different resistance values ​​by changing the input voltage.

6. a switching circuit disposed between the first terminal and the second terminal; the switching circuit includes a plurality of transistors and a plurality of resistor elements; 2. The semiconductor integrated circuit according to claim 1, wherein a state of the switching circuit is switched by a change in the input voltage, and a combination of the resistive elements functioning as a resistor between the first terminal and the second terminal is changed.

7. the plurality of transistors includes a first transistor disposed between a terminal to which the input voltage is applied and the second terminal; The semiconductor integrated circuit according to claim 6 , wherein the first transistor is diode-connected.

8. the plurality of transistors includes a plurality of the first transistors, The semiconductor integrated circuit according to claim 7 , wherein the plurality of first transistors are connected in series.

9. 7. The semiconductor integrated circuit according to claim 6, wherein said plurality of resistance elements includes a resistance element connected between said first terminal and said second terminal without a transistor therebetween.

10. the plurality of transistors includes a second transistor disposed between the first terminal and the second terminal; 7. The semiconductor integrated circuit according to claim 6, wherein said plurality of resistive elements includes a resistive element connected in series with said second transistor between said first terminal and said second terminal.

11. a third terminal; The semiconductor integrated circuit according to claim 1 , wherein the third terminal is a terminal to which the input voltage is applied.

12. The semiconductor integrated circuit according to claim 1 , wherein the first terminal is a terminal to which the input voltage is applied.

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