Semiconductor circuit and determination method

Abstract

The objective is to provide a semiconductor circuit and determination method that can easily determine the region in which the reference voltage is stable. [Solution] The semiconductor circuit of the embodiment includes a bandgap reference circuit section that generates a reference voltage and a detection circuit section. The bandgap reference circuit section includes a control transistor positioned between a wiring to which a first power supply voltage is applied and a reference voltage wiring, and a control circuit section that applies a drive voltage to the control transistor so that the reference voltage becomes a first predetermined value. The control transistor has a first terminal connected to the wiring to which the first power supply voltage is applied, a second terminal connected to the reference voltage wiring, and a drive terminal. The control transistor turns ON when the voltage of the drive terminal, with the voltage of the first terminal as a reference, is a negative value and below a threshold. The detection circuit section includes a first determination circuit section that outputs a signal indicating whether or not the reference voltage is stable at the first predetermined value based on the drive voltage output from the control circuit section.

Description

Technical Field

[0001] Embodiments of the present invention relate to a semiconductor circuit and a determination method.

Background Art

[0002] A bandgap reference (BGR) circuit that generates a reference voltage is known. In the bandgap reference circuit, when the value of the power supply voltage applied to the bandgap reference circuit is low, there is a problem that the generated reference voltage becomes unstable. Therefore, when using the reference voltage generated by the bandgap reference circuit, it is necessary to take measures to suppress the occurrence of an incorrect output in the region where the reference voltage becomes unstable. Conventionally, for example, a voltage region where the reference voltage becomes unstable is specified in advance, and a threshold value based on the value of the specified region is set, so that determination using the reference voltage is not performed in the voltage region where the reference voltage becomes unstable. However, in this case, since it is necessary to specify and set the threshold value in advance, there is a problem that the circuit design is time-consuming.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem to be solved by the present invention is to provide a semiconductor circuit and a determination method capable of easily determining a region where a reference voltage is stable.

Means for Solving the Problems

[0005] The semiconductor circuit of the embodiment includes a bandgap reference circuit section that generates a reference voltage and a detection circuit section. The bandgap reference circuit section includes a control transistor positioned between a wiring to which a first power supply voltage is applied and a reference voltage wiring to which the reference voltage is applied, and a control circuit section that applies a drive voltage to the control transistor so that the reference voltage becomes a first predetermined value. The control transistor has a first terminal connected to the wiring to which the first power supply voltage is applied, a second terminal connected to the reference voltage wiring, and a drive terminal to which the drive voltage is applied. The control transistor turns ON when the voltage of the drive terminal, with the voltage of the first terminal as a reference, is a negative value and below a threshold. The detection circuit section includes a first determination circuit section that outputs a signal indicating whether or not the reference voltage is stable at the first predetermined value based on the drive voltage output from the control circuit section. [Brief explanation of the drawing]

[0006] [Figure 1] A circuit diagram showing a semiconductor circuit of the first embodiment. [Figure 2] This figure shows an example of how the BGR power supply voltage and reference voltage change when the circuit power supply voltage of the first embodiment is changed. [Figure 3] This figure shows an example of how the BGR power supply voltage, drive voltage, first voltage, second voltage, third voltage, fourth voltage, fifth voltage, and output voltage change when the circuit power supply voltage of the first embodiment is varied. [Figure 4] A circuit diagram showing a semiconductor circuit of the second embodiment. [Figure 5] A circuit diagram showing a semiconductor circuit of the third embodiment. [Modes for carrying out the invention]

[0007] The semiconductor circuit and determination method of the embodiment will be described below with reference to the drawings.

[0008] (First embodiment) Figure 1 is a circuit diagram showing a semiconductor circuit 100 of a first embodiment. As shown in Figure 1, the semiconductor circuit 100 comprises a power supply unit 10, a bandgap reference circuit unit 20, and a detection circuit unit 30. The power supply unit 10 applies the BGR power supply voltage Vs to the bandgap reference circuit unit 20. In the first embodiment, the power supply unit 10 is a regulator circuit that generates the BGR power supply voltage Vs using the circuit power supply voltage VDD applied to the semiconductor circuit 100. In other words, in the first embodiment, the BGR power supply voltage Vs is a voltage generated based on the circuit power supply voltage VDD. The power supply unit 10 outputs the BGR power supply voltage Vs to the wiring 11. The wiring 11 is the wiring to which the BGR power supply voltage Vs is applied. In the first embodiment, the BGR power supply voltage Vs corresponds to the "first power supply voltage". The circuit power supply voltage VDD is a voltage referenced to the reference potential VSS. In the first embodiment, the circuit power supply voltage VDD corresponds to the "second power supply voltage". The reference potential VSS is the reference potential in the semiconductor circuit 100. The reference potential VSS is not particularly limited, as long as it is the reference potential for the semiconductor circuit 100. The power supply unit 10 is placed between the power supply voltage wiring 41 to which the circuit power supply voltage VDD is applied and the ground 42 which is the reference potential VSS. The power supply unit 10 may also be a circuit that short-circuits the power supply voltage wiring 41 and wiring 11. In this case, the BGR power supply voltage Vs will be equal to the circuit power supply voltage VDD.

[0009] In the circuit of this disclosure, "another element is placed between one element and another element" means that the other element is provided on the circuit between one element and the other element, from one to the other.

[0010] The bandgap reference circuit section 20 generates a reference voltage Vr. The bandgap reference circuit section 20 includes a reference voltage wiring 20a, a control circuit section 21, a control transistor 22, bipolar transistors 23 and 24, and resistor elements 25a, 25b, and 25c. The reference voltage wiring 20a is the wiring to which the reference voltage Vr is applied.

[0011] The control transistor 22 is positioned between the wiring 11 to which the BGR power supply voltage Vs is applied and the reference voltage wiring 20a to which the reference voltage Vr is applied. In the first embodiment, the control transistor 22 is a P-channel field-effect transistor (FET). More specifically, the control transistor 22 is a P-channel MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The control transistor 22 has a source terminal 22s, a drain terminal 22d, and a gate terminal 22g. The source terminal 22s is connected to the wiring 11. The drain terminal 22d is connected to the reference voltage wiring 20a. A drive voltage Vd is applied to the gate terminal 22g from the control circuit unit 21. In the first embodiment, the source terminal 22s corresponds to the "first terminal," the drain terminal 22d corresponds to the "second terminal," and the gate terminal 22g corresponds to the "drive terminal." The control transistor 22 turns ON when the voltage at the gate terminal 22g, referenced to the voltage at the source terminal 22s, i.e., the gate-source voltage, is a negative value and below a threshold.

[0012] In the first embodiment, bipolar transistors 23 and 24 are NPN type bipolar transistors. In each of the bipolar transistors 23 and 24, the collector terminal C and the base terminal B are connected to each other. In other words, each of the bipolar transistors 23 and 24 is diode-connected.

[0013] Resistors 25a and 25b and a bipolar transistor 23 are connected in series and placed between the reference voltage wiring 20a and ground 42. One end of resistor 25a is connected to the reference voltage wiring 20a. The other end of resistor 25a is connected to one end of resistor 25b. The other end of resistor 25b is connected to the collector terminal C of the bipolar transistor 23. The emitter terminal E of the bipolar transistor 23 is connected to ground 42. The series connection of resistors 25a and 25b and the bipolar transistor 23 forms a first current path 26a. The first current path 26a connects the reference voltage wiring 20a and ground 42. The resistance values ​​of resistors 25a and 25b are not particularly limited.

[0014] The resistor 25c and the bipolar transistor 24 are connected in series and placed between the reference voltage wiring 20a and ground 42. One end of the resistor 25c is connected to the reference voltage wiring 20a. The other end of the resistor 25c is connected to the collector terminal C of the bipolar transistor 24. The emitter terminal E of the bipolar transistor 24 is connected to ground 42. The series connection of the resistor 25c and the bipolar transistor 24 forms a second current path 26b. The second current path 26b connects the reference voltage wiring 20a and ground 42. The first current path 26a and the second current path 26b are arranged in parallel with each other between the reference voltage wiring 20a and ground 42. The resistance value of the resistor 25c is not particularly limited.

[0015] The control circuit unit 21 applies a drive voltage Vd to the control transistor 22 so that the reference voltage Vr becomes a first predetermined value Ve. The control circuit unit 21 receives the voltage Va in the portion of the first current path 26a between resistor element 25a and resistor element 25b, and the voltage Vb in the portion of the second current path 26b between resistor element 25c and bipolar transistor 24 as input. The control circuit unit 21 adjusts the value of the drive voltage Vd so that voltage Va and voltage Vb are equal to each other. In the first embodiment, the bandgap reference circuit unit 20 is configured such that when voltage Va and voltage Vb are equal to each other, the value of the generated reference voltage Vr becomes a first predetermined value Ve. The first predetermined value Ve is, for example, about 1.2V.

[0016] Furthermore, the statement "the control circuit unit 21 applies a drive voltage Vd to the control transistor 22 so that the reference voltage Vr becomes a first predetermined value Ve" means that the control circuit unit 21 only needs to control the value of the drive voltage Vd with the first predetermined value Ve as the target value for the reference voltage Vr, and it is acceptable that the reference voltage Vr does not become the first predetermined value Ve as a result of applying the drive voltage Vd to the control transistor 22. For example, as will be described later, if the BGR power supply voltage Vs is lower than a certain value, the reference voltage Vr will not become the first predetermined value Ve no matter how the drive voltage Vd is adjusted. In this case, the control circuit unit 21 controls the drive voltage Vd so that the reference voltage Vr becomes a value close to the first predetermined value Ve within the range that can be adjusted by the drive voltage Vd.

[0017] The detection circuit unit 30 can detect, based on a reference voltage Vr, when the circuit power supply voltage VDD falls below a second predetermined value VDDa. The second predetermined value VDDa is a value that is appropriately set based on the voltage value required for a circuit using the circuit power supply voltage VDD, and is not particularly limited. The detection circuit unit 30 is connected to the bandgap reference circuit unit 20. The detection circuit unit 30 includes a first determination circuit unit 31, a second determination circuit unit 32, a third determination circuit unit 33, and resistor elements 34a, 34b, 34c, and 34d.

[0018] The resistance elements 34a and 34b are connected in series and are arranged between the reference voltage wiring 20a and the ground 42. One end of the resistance element 34a is connected to the reference voltage wiring 20a. The other end of the resistance element 34a is connected to one end of the resistance element 34b. The other end of the resistance element 34b is connected to the ground 42. The resistance values of the resistance elements 34a and 34b are appropriately set based on, for example, what values the first voltage V1 and the second voltage V2, which will be described later, are to take.

[0019] The resistance elements 34c and 34d are connected in series and are arranged between the power supply voltage wiring 41 and the ground 42. One end of the resistance element 34c is connected to the power supply voltage wiring 41. The other end of the resistance element 34c is connected to one end of the resistance element 34d. The other end of the resistance element 34d is connected to the ground 42. The resistance values of the resistance elements 34c and 34d are appropriately set based on, for example, what value the third voltage V3, which will be described later, is to take.

[0020] The drive voltage Vd output from the control circuit unit 21 and the first voltage V1 are input to the first determination circuit unit 31. The first voltage V1 is a voltage based on the reference voltage Vr. In the first embodiment, the first voltage V1 is the voltage obtained by dividing the reference voltage Vr by the resistance elements 34a and 34b, that is, the resistance division of the reference voltage Vr. The first voltage V1 is the voltage between the resistance element 34a and the resistance element 34b. The value of the first voltage V1 is determined by the value of the reference voltage Vr and the ratio of the resistance element 34a to the resistance element 34b.

[0021] The first determination circuit unit 31 is a comparator that compares the drive voltage Vd and the first voltage V1 and outputs the fourth voltage V4. When the drive voltage Vd is higher than the first voltage V1, the first determination circuit unit 31 sets the level of the output fourth voltage V4 to high. When the drive voltage Vd is less than or equal to the first voltage V1, the first determination circuit unit 31 sets the level of the output fourth voltage V4 to low.

[0022] The second determination circuit section 32 receives the second voltage V2 and the third voltage V3. The second voltage V2 is a voltage based on the reference voltage Vr. In the first embodiment, the second voltage V2 is the voltage obtained by dividing the reference voltage Vr by the resistance elements 34a and 34b, that is, the resistive voltage division of the reference voltage Vr. The second voltage V2 is the voltage between the resistance element 34a and the resistance element 34b. The value of the second voltage V2 is determined by the value of the reference voltage Vr and the ratio between the resistance element 34a and the resistance element 34b. In the first embodiment, the value of the second voltage V2 is the same as the value of the first voltage V1. The third voltage V3 is a voltage based on the circuit power supply voltage VDD. In the first embodiment, the third voltage V3 is the voltage obtained by dividing the circuit power supply voltage VDD by the resistance elements 34c and 34d, that is, the resistive voltage division of the circuit power supply voltage VDD. The third voltage V3 is the voltage between the resistance element 34c and the resistance element 34d. The value of the third voltage V3 is determined by the value of the circuit power supply voltage VDD and the ratio between the resistance element 34c and the resistance element 34d. <> <>

[0023] <> The second determination circuit section 32 is a comparator that compares the second voltage V2 and the third voltage V3 and outputs the fifth voltage V5. When the third voltage V3 is higher than the second voltage V2, the second determination circuit section 32 sets the level of the output fifth voltage V5 to high. When the third voltage V3 is less than or equal to the second voltage V2, the second determination circuit section 32 sets the level of the output fifth voltage V5 to low. <> <>

[0024] <> Note that between the resistance element 34a and the wiring portion that becomes the first voltage V1 connected to the first determination circuit section 31, between the wiring portion that becomes the first voltage V1 connected to the first determination circuit section 31 and the wiring portion that becomes the second voltage V2 connected to the second determination circuit section 32, and between the wiring portion that becomes the second voltage V2 connected to the second determination circuit section 32 and the resistance element 34b, at least one or more other resistance elements may be arranged respectively. <> <>

[0025] <> The third determination circuit 33 receives the signal output from the first determination circuit 31, i.e., the fourth voltage V4, and the signal output from the second determination circuit 32, i.e., the fifth voltage V5. The third determination circuit 33 outputs an output voltage Vt based on the fourth voltage V4 and the fifth voltage V5. The output voltage Vt is the output signal of the detection circuit 30. In the first embodiment, the third determination circuit 33 is an AND gate. The third determination circuit 33 sets the level of the output output voltage Vt to high when both the level of the fourth voltage V4 and the level of the fifth voltage V5 are high. The third determination circuit 33 sets the level of the output output voltage Vt to low when at least one of the levels of the fourth voltage V4 and the fifth voltage V5 is low. In other words, the third determination circuit 33 sets the level of the output output voltage Vt to low when the level of the fourth voltage V4 is low and the level of the fifth voltage V5 is low.

[0026] When the output voltage Vt level is high, the circuit power supply voltage VDD is greater than or equal to the second predetermined value VDDa. In other words, when the output voltage Vt level is high, the output voltage Vt is a signal indicating that the circuit power supply voltage VDD is greater than or equal to the second predetermined value VDDa. As described above, the output voltage Vt level is high when both the fourth voltage V4 level and the fifth voltage V5 level are high. In the first embodiment, the predetermined condition is met when both the fourth voltage V4 level and the fifth voltage V5 level are high. When the predetermined condition is met, the third determination circuit 33 outputs an output voltage Vt with a high level as a signal indicating that the circuit power supply voltage VDD is greater than or equal to the second predetermined value VDDa. When the output voltage Vt level is low, the circuit power supply voltage VDD is lower than the second predetermined value VDDa. In other words, when the output voltage Vt level is low, the output voltage Vt is a signal indicating that the circuit power supply voltage VDD is lower than the second predetermined value VDDa. If the above predetermined conditions are not met, the third determination circuit 33 outputs an output voltage Vt with a low level as a signal indicating that the circuit power supply voltage VDD is lower than the second predetermined value VDDa.

[0027] Figure 2 shows an example of the changes in BGR power supply voltage Vs and reference voltage Vr when the circuit power supply voltage VDD is changed. The top graph in Figure 2 shows the change in circuit power supply voltage VDD. The middle graph in Figure 2 shows the change in BGR power supply voltage Vs. The bottom graph in Figure 2 shows the change in reference voltage Vr. Figure 3 shows an example of the changes in BGR power supply voltage Vs, drive voltage Vd, first voltage V1, second voltage V2, third voltage V3, fourth voltage V4, fifth voltage V5, and output voltage Vt when the circuit power supply voltage VDD is changed. The top graph in Figure 3 shows the changes in BGR power supply voltage Vs, drive voltage Vd, and first voltage V1. The second graph from the top in Figure 3 shows the change in fourth voltage V4. The third graph from the top in Figure 3 shows the changes in second voltage V2 and third voltage V3. The second graph from the bottom in Figure 3 shows the change in fifth voltage V5. The bottom graph in Figure 3 shows the change in output voltage Vt. In the graphs in Figures 2 and 3, the horizontal axis represents time t.

[0028] Examples in Figures 2 and 3 show the changes in each voltage when the circuit power supply voltage VDD is varied from time t0 to time t10. As shown in Figure 2, the circuit power supply voltage VDD increases linearly from value VDD1 to value VDD2 between time t0 and time t5, and decreases linearly from value VDD2 to value VDD1 between time t5 and time t10. Value VDD1 is lower than the second predetermined value VDDa. Value VDD2 is higher than the second predetermined value VDDa. As shown in Figure 3, the third voltage V3 is a resistive voltage divider of the circuit power supply voltage VDD, so although its magnitude is different, it changes similarly to the circuit power supply voltage VDD between time t0 and time t10.

[0029] As shown in Figure 2, when the circuit power supply voltage VDD changes, the BGR power supply voltage Vs, which is based on the circuit power supply voltage VDD, also changes in the same way as the circuit power supply voltage VDD. The BGR power supply voltage Vs increases linearly from value Vs1 to value Vs2 between time t0 and time t5, and then decreases linearly from value Vs2 to value Vs1 between time t5 and time t10.

[0030] The reference voltage Vr is less than the first predetermined value Ve from time t0 until before time t2. When time t2 arrives and the BGR power supply voltage Vs becomes a third predetermined value Vsa, which is greater than the value Vs1, the reference voltage Vr becomes the first predetermined value Ve. Between time t0 and time t2, the reference voltage Vr increases as the BGR power supply voltage Vs increases. Between time t2 and time t8, the BGR power supply voltage Vs is greater than or equal to the third predetermined value Vsa, and the reference voltage Vr is maintained constant at the first predetermined value Ve. In other words, in the first embodiment, when the BGR power supply voltage Vs is greater than or equal to the third predetermined value Vsa, the reference voltage Vr stabilizes at the first predetermined value Ve. After time t8 has passed and the BGR power supply voltage Vs falls below the third predetermined value Vsa, the reference voltage Vr falls below the first predetermined value Ve. Between time t8 and time t10, the reference voltage Vr decreases as the BGR power supply voltage Vs decreases. The third predetermined value Vsa is higher than value Vs1 and lower than value Vs2. The third predetermined value Vsa is, for example, the same value as the first predetermined value Ve. The third predetermined value Vsa may be a different value from the first predetermined value Ve.

[0031] As shown in Figure 3, the first voltage V1 and the second voltage V2 are resistive voltage dividers of the reference voltage Vr, and therefore, although their voltage values ​​are different in magnitude, they change similarly to the reference voltage Vr from time t0 to time t10. In the first embodiment, the first voltage V1 and the second voltage V2 are the same value, so the first voltage V1 and the second voltage V2 are kept constant at a predetermined voltage divide value Ve1 between time t2 and time t8. The predetermined voltage divide value Ve1 is lower than the first predetermined value Ve.

[0032] At time t0, the value Vs1 of the BGR power supply voltage Vs is greater than the absolute value of the threshold of the control transistor 22. Therefore, when the BGR power supply voltage Vs is applied to the source terminal 22s of the control transistor 22 at time t0, the gate-source voltage of the control transistor 22 becomes below the threshold, and the control transistor 22 turns ON. When the control transistor 22 turns ON, current flows from the power supply unit 10 to the first current path 26a and the second current path 26b, and a reference voltage Vr is generated in the reference voltage wiring 20a. If the BGR power supply voltage Vs is lower than the third predetermined value Vsa, the voltages Va and Vb input to the control circuit unit 21 will not be the same value, and the reference voltage Vr will be lower than the first predetermined value Ve. In this case, the control circuit unit 21 increases the current flowing through the control transistor 22 to raise the reference voltage Vr by increasing the current flowing through the control transistor 22 in order to make the voltages Va and Vb the same value, and sets the drive voltage Vd to zero or nearly zero. Therefore, as shown in Figure 3, the drive voltage Vd is almost zero from time t0 until just before time t2 when the BGR power supply voltage Vs is low and the reference voltage Vr cannot be set to the first predetermined value Ve. When the reference voltage Vr is lower than the first predetermined value Ve, the current flowing through the control transistor 22 and the reference voltage Vr increase as the BGR power supply voltage Vs rises.

[0033] In the examples in Figures 2 and 3, when the BGR power supply voltage Vs reaches the third predetermined value Vsa at time t2, voltages Va and Vb become the same value, and the reference voltage Vr becomes the first predetermined value Ve. However, if the drive voltage Vd remains zero or nearly zero while the BGR power supply voltage Vs rises above the third predetermined value Vsa, voltages Va and Vb become different values, and the reference voltage Vr rises above the first predetermined value Ve. The control circuit 21 increases the drive voltage Vd when the BGR power supply voltage Vs rises above the third predetermined value Vsa in order to maintain the state in which voltages Va and Vb are the same value. Specifically, the control circuit 21 increases the drive voltage Vd so that the voltage difference between the source terminal 22s and the gate terminal 22g of the control transistor 22 becomes a constant value Vc. In other words, the control circuit 21 increases the drive voltage Vd so that the voltage difference between the BGR power supply voltage Vs and the drive voltage Vd becomes a constant value Vc. The value Vc will be, for example, approximately the threshold value of the control transistor 22. The value Vc is, for example, about 0.7V.

[0034] As shown in Figure 3, after time t2, when the BGR power supply voltage Vs becomes greater than the third predetermined value Vsa, the drive voltage Vd rises sharply, and then rises linearly as the BGR power supply voltage Vs rises until time t5. The drive voltage Vd rises linearly as the BGR power supply voltage Vs rises from the time when the difference between the drive voltage Vd and the BGR power supply voltage Vs becomes value Vc. In the example in Figure 3, at time t3a, which is after time t3, the difference between the drive voltage Vd and the BGR power supply voltage Vs becomes value Vc. The value of the BGR power supply voltage Vs at time t3a is the fourth predetermined value Vsb, which is higher than the third predetermined value Vsa. After time t5, when the BGR power supply voltage Vs begins to fall, the drive voltage Vd begins to fall together with the BGR power supply voltage Vs, and after time t6a, which is after time t6, when the BGR power supply voltage Vs becomes lower than the fourth predetermined value Vsb, it drops sharply, and thereafter becomes zero or nearly zero. Time t3a is before time t4. Time t6a is before time t7.

[0035] The first determination circuit 31 compares the fluctuating drive voltage Vd with the first voltage V1 as described above and outputs the fourth voltage V4. Between time t0 and time t2, the drive voltage Vd is zero or nearly zero, so the drive voltage Vd is lower than the first voltage V1. In this case, the first determination circuit 31 sets the level of the fourth voltage V4 to low (L). After time t2, when the drive voltage Vd rises sharply and becomes higher than the first voltage V1, the first determination circuit 31 sets the level of the fourth voltage V4 to high (H). In the example in Figure 3, at time t3, the drive voltage Vd is the same value as the first voltage V1, so after time t3, the first determination circuit 31 sets the level of the fourth voltage V4 to high (H). Between time t2 and time t8, the first voltage V1 is constant at a predetermined voltage divider value Ve1. Therefore, between time t3 and time t7, when the drive voltage Vd is higher than the predetermined voltage divider value Ve1, the level of the fourth voltage V4 remains high (H). After time t7, when the drive voltage Vd falls below the predetermined voltage divider value Ve1, the level of the fourth voltage V4 becomes low (L).

[0036] Here, the drive voltage Vd rises sharply from zero or near zero when the BGR power supply voltage Vs becomes higher than the third predetermined value Vsa, and the reference voltage Vr becomes the first predetermined value Ve. Therefore, when the drive voltage Vd becomes higher than the first voltage V1, the BGR power supply voltage Vs is a value that can stabilize the reference voltage Vr at the first predetermined value Ve. Consequently, when the level of the fourth voltage V4 is high (H), the BGR power supply voltage Vs is a value that can stabilize the reference voltage Vr at the first predetermined value Ve, and the reference voltage Vr is at the first predetermined value Ve.

[0037] On the other hand, when the level of the fourth voltage V4 is low (L), the BGR power supply voltage Vs will be lower than the third predetermined value Vsa and the reference voltage Vr will be lower than the first predetermined value Ve, except for a short period of time from time t2 to time t3 and from time t7 to time t8 when the drive voltage Vd changes rapidly. Therefore, when the level of the fourth voltage V4 is low (L), the BGR power supply voltage Vs can be considered to be a value that is not large enough to stabilize the reference voltage Vr at the first predetermined value Ve.

[0038] Thus, the first determination circuit 31 outputs a fourth voltage V4 as a signal indicating whether or not the reference voltage Vr is stable at a first predetermined value Ve, based on the drive voltage Vd output from the control circuit 21. The first determination circuit 31 outputs a fourth voltage V4 with a high level as a signal indicating that the reference voltage Vr is stable at a first predetermined value Ve, when the drive voltage Vd is higher than the first voltage V1. The determination performed by the first determination circuit 31 is a determination method of the first embodiment for determining the reference voltage Vr generated by the bandgap reference circuit 20. The determination method includes determining whether or not the reference voltage Vr is stable at a first predetermined value Ve, based on the drive voltage Vd output from the control circuit 21. The determination method includes determining that the reference voltage Vr is stable at a first predetermined value Ve when the drive voltage Vd is higher than the first voltage V1 based on the reference voltage Vr.

[0039] The second determination circuit 32 compares the third voltage V3, which is the resistive voltage divide of the circuit power supply voltage VDD, with the second voltage V2, which is the resistive voltage divide of the reference voltage Vr, to determine whether the circuit power supply voltage VDD has fallen below the second predetermined value VDDa. Here, if the reference voltage Vr is always at the first predetermined value Ve, it is possible to determine whether the circuit power supply voltage VDD has fallen below the second predetermined value VDDa based solely on the determination result of the second determination circuit 32. However, as described above, if the BGR power supply voltage Vs is lower than the third predetermined value Vsa, the reference voltage Vr becomes unstable and lower than the first predetermined value Ve. Therefore, if the BGR power supply voltage Vs is lower than the third predetermined value Vsa, the second determination circuit 32 may produce an incorrect output.

[0040] In the example shown in Figure 3, the third voltage V3 is higher than the second voltage V2 between time t0 and time t1, between time t4 and time t6, and between time t9 and time t10, and the level of the fifth voltage V5 is high (H). Between time t2 and time t8, when the second voltage V2 stabilizes at a constant predetermined voltage divider value Ve1, at times t4 and t6, when the value of the third voltage V3 is the same as the value of the second voltage V2, i.e., the predetermined voltage divider value Ve1, the circuit power supply voltage VDD becomes the second predetermined value VDDa, as shown in Figure 2. Therefore, between time t4 and time t6, the circuit power supply voltage VDD is greater than or equal to the second predetermined value VDDa. Consequently, the fact that the level of the fifth voltage V5 is high (H) between time t4 and time t6 is normal operation of the second determination circuit 32. On the other hand, between time t0 and time t1, and between time t9 and time t10, the circuit power supply voltage VDD is lower than the second predetermined value VDDa. Therefore, if the second determination circuit 32 is performing its determination operation correctly, the level of the fifth voltage V5 will be low (L) between time t0 and time t1, and between time t9 and time t10. However, between time t0 and time t1, and between time t9 and time t10, the reference voltage Vr is unstable and lower than the first predetermined value Ve. As a result, even though the circuit power supply voltage VDD is lower than the second predetermined value VDDa, the third voltage V3 becomes higher than the second voltage V2, and the level of the fifth voltage V5 becomes high (H). In other words, between time t0 and time t1, and between time t9 and time t10, the second determination circuit 32 is outputting an incorrect value.

[0041] In the first embodiment, even if the second determination circuit 32 outputs an incorrect value as described above, the first determination circuit 31 and the third determination circuit 33 are provided to suppress the output voltage Vt that is ultimately output incorrectly. As described above, the fourth voltage V4 output from the first determination circuit 31 is a signal indicating whether or not the reference voltage Vr is stable at a first predetermined value Ve. Therefore, in the determination made by the second determination circuit 32 when the level of the fourth voltage V4 is high (H), the reference voltage Vr is stable at the first predetermined value Ve, thus suppressing the occurrence of the incorrect output described above.

[0042] Here, the third determination circuit 33 sets the output voltage Vt level to high (H) only when both the level of the fourth voltage V4 input from the first determination circuit 31 and the level of the fifth voltage V5 input from the second determination circuit 32 are high (H). Therefore, in the example in Figure 3, the output voltage Vt level is high (H) only from time t4 to time t6, when the level of the fifth voltage V5 is high (H), within the period from time t3 to time t7 when the level of the fourth voltage V4 is high (H). In this way, by providing the first determination circuit 31 and the third determination circuit 33, even if the level of the fifth voltage V5 is high (H) when the reference voltage Vr is unstable, the output voltage Vt level will not be high (H). Therefore, the erroneous output of the output voltage Vt is suppressed.

[0043] The voltage range in which the first determination circuit 31 operates includes the voltage range in which the second determination circuit 32 operates. The voltage range in which the first determination circuit 31 operates is the same as or wider than the voltage range in which the second determination circuit 32 operates. As a result, the second determination circuit 32 will not operate in the voltage range in which the first determination circuit 31 does not operate. Therefore, the first determination circuit 31 will not fail to operate if the second determination circuit 32 outputs an incorrect value, and the incorrect output voltage Vt can be effectively suppressed.

[0044] The value of the BGR power supply voltage Vs at the threshold for operation of the second determination circuit 32 is greater than the value of the BGR power supply voltage Vs at which the reference voltage Vr fails. The threshold for operation of the second determination circuit 32 is the value at which the level of the output fifth voltage V5 switches between high and low when the second determination circuit 32 is operating normally. The value of the BGR power supply voltage Vs at which the reference voltage Vr fails is a value where the BGR power supply voltage Vs is lower than the voltage values ​​shown in Figures 2 and 3, and the reference voltage Vr can no longer be generated. If the value of the BGR power supply voltage Vs at the threshold for operation of the second determination circuit 32 is less than or equal to the value of the BGR power supply voltage Vs at which the reference voltage Vr fails, the level of the fifth voltage V5 will be high (H) in the entire voltage range in which the reference voltage Vr is generated, and the second determination circuit 32 will not operate normally.

[0045] According to the first embodiment, the semiconductor circuit 100 includes a bandgap reference circuit section 20 that generates a reference voltage Vr, and a detection circuit section 30. The bandgap reference circuit section 20 includes a control transistor 22 positioned between a wiring 11 to which a BGR power supply voltage Vs (first power supply voltage) is applied and a reference voltage wiring 20a to which a reference voltage Vr is applied, and a control circuit section 21 that applies a drive voltage Vd to the control transistor 22 so that the reference voltage Vr becomes a first predetermined value Ve. The control transistor 22 has a source terminal 22s (first terminal) connected to the wiring to which the BGR power supply voltage Vs is applied, a drain terminal 22d (second terminal) connected to the reference voltage wiring 20a, and a gate terminal 22g (drive terminal) to which a drive voltage Vd is applied, and turns ON when the voltage of the gate terminal 22g, referenced to the voltage of the source terminal 22s, is a negative value and less than or equal to a threshold. The detection circuit unit 30 includes a first determination circuit unit 31 that outputs a signal indicating whether or not the reference voltage Vr is stable at a first predetermined value Ve, based on the drive voltage Vd output from the control circuit unit 21. In other words, the determination method of the first embodiment includes determining whether or not the reference voltage Vr is stable at a first predetermined value Ve, based on the drive voltage Vd output from the control circuit unit 21.

[0046] The control circuit unit 21 controls the control transistor 22 so that the reference voltage Vr becomes a first predetermined value Ve. Therefore, if the BGR power supply voltage Vs is lower than the value that can stabilize the reference voltage Vr at the first predetermined value Ve, the control circuit unit 21 attempts to increase the reference voltage Vr by putting the control transistor 22 into a state where more current can flow. Since the control transistor 22 turns ON when the voltage at the gate terminal 22g, referenced to the voltage at the source terminal 22s, is a negative value and below a threshold, the control circuit unit 21 sets the drive voltage Vd to zero or nearly zero until the BGR power supply voltage Vs becomes a value that can stabilize the reference voltage Vr at the first predetermined value Ve. On the other hand, if the BGR power supply voltage Vs becomes greater than the value that makes the reference voltage Vr a first predetermined value Ve, the control circuit unit 21 increases the drive voltage Vd to prevent the current flowing through the control transistor 22 from becoming too high and causing the reference voltage Vr to exceed the first predetermined value Ve. Therefore, when the BGR power supply voltage Vs becomes greater than or equal to a value that can stabilize the reference voltage Vr at a first predetermined value Ve, the drive voltage Vd rises from zero or nearly zero. Thus, by determining whether the drive voltage Vd has risen from zero or nearly zero using the first determination circuit 31, it is possible to determine whether the reference voltage Vr is stable at the first predetermined value Ve. The drive voltage Vd is a value that is automatically adjusted by the control circuit 21 in response to changes in the BGR power supply voltage Vs. Therefore, even if the designer of the semiconductor circuit 100 does not set a threshold in advance, it is possible to determine whether the reference voltage Vr is stable by making a determination using the first determination circuit 31 based on the drive voltage Vd. Thus, the region in which the reference voltage Vr is stable can be easily determined.

[0047] According to the first embodiment, the first determination circuit 31 receives a drive voltage Vd and a first voltage V1 based on a reference voltage Vr as inputs. When the drive voltage Vd is higher than the first voltage V1, the first determination circuit 31 outputs a signal indicating that the reference voltage Vr is stable at a first predetermined value Ve, i.e., a fourth voltage V4 with a high level. In other words, the determination method of the first embodiment includes determining that the reference voltage Vr is stable at a first predetermined value Ve when the drive voltage Vd is higher than the first voltage V1 based on the reference voltage Vr. Since the reference voltage Vr is maintained at the first predetermined value Ve once it stabilizes, when the reference voltage Vr stabilizes, the first voltage V1 based on the reference voltage Vr is also maintained at a predetermined voltage divide value Ve1. Therefore, when the drive voltage Vd starts to rise, the first voltage V1 is at the predetermined voltage divide value Ve1. Therefore, the first determination circuit 31 can easily determine that the reference voltage Vr is stable by determining that the rising drive voltage Vd has become higher than a predetermined voltage divider value Ve1.

[0048] According to the first embodiment, the first voltage V1 is a resistive voltage divider of the reference voltage Vr. Therefore, the first voltage V1 is lower than the reference voltage Vr. As a result, the predetermined voltage divide value Ve1 at which the first voltage V1 stabilizes is also lower than the first predetermined value Ve at which the reference voltage Vr stabilizes. Therefore, when the reference voltage Vr reaches the first predetermined value Ve and the drive voltage Vd rises, the value of the BGR power supply voltage Vs at which the drive voltage Vd becomes equal to the predetermined voltage divide value Ve1 can be reduced. As a result, the value of the BGR power supply voltage Vs at which the drive voltage Vd becomes higher than the predetermined voltage divide value Ve1 can be kept low within a range that allows the reference voltage Vr to be stabilized. Consequently, the range of BGR power supply voltage Vs at which the first determination circuit 31 can determine that the reference voltage Vr is stable can be suitably widened. It is preferable that the value at which the first voltage V1 stabilizes, i.e., the predetermined voltage divider value Ve1, is set to be, for example, higher than 0V and within a range of less than or equal to the smallest value of the drive voltage Vd among the values ​​of the drive voltage Vd where the difference with the BGR power supply voltage Vs is value Vc. The value of the drive voltage Vd where the difference with the BGR power supply voltage Vs is value Vc is the value of the drive voltage Vd from time t3a to time t6a. The smallest value of the drive voltage Vd among the values ​​of the drive voltage Vd where the difference with the BGR power supply voltage Vs is value Vc is the value of the drive voltage Vd at times t3a and t6a. By setting the predetermined voltage divider value Ve1 to be higher than 0V and less than or equal to the smallest value of the drive voltage Vd, the value of the drive voltage Vd can be made to be greater than or equal to the value of the first voltage V1 throughout the entire range in which the difference of the drive voltage Vd with respect to the BGR power supply voltage Vs changes by value Vc. The range in which the difference of the drive voltage Vd with respect to the BGR power supply voltage Vs changes by value Vc is the region in which the reference voltage Vr is stable. Therefore, by setting the predetermined voltage divider value Ve1 for which the first voltage V1 is stable as described above, the range of BGR power supply voltage Vs in which the first determination circuit 31 can determine that the reference voltage Vr is stable, that is, the range in which the fourth voltage V4 is high (H), can be more favorably widened.

[0049] In the first embodiment, the predetermined voltage divide value Ve1 at which the first voltage V1 stabilizes is less than or equal to the value obtained by subtracting the value Vc from the first predetermined value Ve. This allows the drive voltage Vd to be the same value as the predetermined voltage divide value Ve1 while the drive voltage Vd rises sharply from time t2 to time t3, and while the drive voltage Vd falls sharply from time t7 to time t8. Therefore, the range of BGR power supply voltage Vs at which the first determination circuit 31 can determine that the reference voltage Vr is stable can be more suitably widened. The predetermined voltage divide value Ve1 shown in Figure 3 is, for example, equal to the value obtained by subtracting the value Vc from the first predetermined value Ve. Note that when the BGR power supply voltage Vs becomes the fourth predetermined value Vsb, the difference between the BGR power supply voltage Vs and the drive voltage Vd becomes the value Vc, and the values ​​of the drive voltage Vd and the predetermined voltage divide value Ve1 may become equal.

[0050] According to the first embodiment, the detection circuit unit 30 has a second determination circuit unit 32 and a third determination circuit unit 33, and is capable of detecting, based on a reference voltage Vr, that the circuit power supply voltage VDD has fallen below a second predetermined value VDDa. The second determination circuit unit 32 receives a second voltage V2 based on the reference voltage Vr and a third voltage V3 based on the circuit power supply voltage VDD as inputs. The third determination circuit unit 33 receives a signal output from the first determination circuit unit 31, i.e., a fourth voltage V4, and a signal output from the second determination circuit unit 32, i.e., a fifth voltage V5. When a predetermined condition is met, the third determination circuit unit 33 outputs a signal indicating that the circuit power supply voltage VDD is equal to or greater than the second predetermined value VDDa, i.e., an output voltage Vt with a high level. The third determination circuit 33 outputs an output voltage Vt that indicates the circuit power supply voltage VDD is lower than the second predetermined value VDDa, i.e., a low level, when the fourth voltage V4 output from the first determination circuit 31 is a signal indicating that the drive voltage Vd is less than or equal to the first voltage V1. The third determination circuit 33 also outputs an output voltage Vt that indicates the circuit power supply voltage VDD is lower than the second predetermined value VDDa, i.e., a low level, when the signal output from the second determination circuit 32 is a signal indicating that the third voltage V3 is less than or equal to the second voltage V2. The predetermined conditions are met when the fourth voltage V4 output from the first determination circuit 31 is a signal indicating that the drive voltage Vd is higher than the first voltage V1, and the fifth voltage V5 output from the second determination circuit 32 is a signal indicating that the third voltage V3 is higher than the second voltage V2. Therefore, even if the second determination circuit 32 outputs an incorrect value when the reference voltage Vr is unstable, the output voltage Vt will not output an incorrect value unless the first determination circuit 31 has determined that the drive voltage Vd is higher than the first voltage V1. Consequently, the detection circuit 30 can accurately monitor the circuit power supply voltage VDD based on the reference voltage Vr.

[0051] According to the first embodiment, the second voltage V2 is a resistive voltage divider of the reference voltage Vr. The third voltage V3 is a resistive voltage divider of the circuit power supply voltage VDD. Therefore, regardless of the magnitudes of the reference voltage Vr and the circuit power supply voltage VDD, the magnitudes of the second voltage V2 and the third voltage V3 compared in the second determination circuit 32 can be adjusted by adjusting the resistance values ​​of the resistive elements 34a to 34d. This makes it possible to set the value of the circuit power supply voltage VDD when the third voltage V3 is equal to the second voltage V2, i.e., the second predetermined value VDDa, regardless of the magnitudes of the reference voltage Vr and the circuit power supply voltage VDD.

[0052] According to the first embodiment, the BGR power supply voltage Vs is a voltage generated based on the circuit power supply voltage VDD. Therefore, the BGR power supply voltage Vs can be generated without providing an external power supply. The effect of easily determining the region in which the reference voltage Vr stabilizes based on the drive voltage Vd is particularly useful when the BGR power supply voltage Vs is a voltage generated based on the circuit power supply voltage VDD. This will be explained in detail below.

[0053] For example, conventionally, instead of the first determination circuit 31, a monitoring circuit was provided to monitor the circuit power supply voltage VDD. When the circuit power supply voltage VDD was equal to or greater than a second predetermined value VDDa, the level of the input from the monitoring circuit to the third determination circuit 33 was set to high, thereby suppressing the occurrence of false outputs when the reference voltage Vr was low and unstable. However, with this method, it was necessary to pre-determine what value of the circuit power supply voltage VDD would cause the reference voltage Vr to become unstable, and to set the threshold of the monitoring circuit based on the determined value. Furthermore, when the BGR power supply voltage Vs is a voltage generated based on the circuit power supply voltage VDD, variations in the characteristics of the circuit that generates the BGR power supply voltage Vs, i.e., the power supply unit 10, cause variations in the value of the BGR power supply voltage Vs relative to the circuit power supply voltage VDD. Therefore, the threshold set in the monitoring circuit that monitors the circuit power supply voltage VDD had to be a threshold that took these variations into account, which resulted in the problem that the voltage range in which the reference voltage Vr could be determined to be stable became unnecessarily narrow.

[0054] To address this problem, according to the first embodiment, as described above, by monitoring the drive voltage Vd with the first determination circuit unit 31, it is easy to determine whether the reference voltage Vr is stable or not. Therefore, it is not necessary to set a range of circuit power supply voltage VDD in which the reference voltage Vr becomes unstable, as is the case with the monitoring circuit unit described above. Furthermore, even when the BGR power supply voltage Vs is generated based on the circuit power supply voltage VDD, the state of the reference voltage Vr can be monitored by the drive voltage Vd. Therefore, even if the BGR power supply voltage Vs fluctuates with respect to the circuit power supply voltage VDD, it is possible to accurately detect that the reference voltage Vr has become stable. Consequently, it is easy to match the voltage range in which the reference voltage Vr can be determined to be stable with the range in which the reference voltage Vr is actually stable at the first predetermined value Ve. As a result, it is possible to suppress the voltage range in which the reference voltage Vr can be determined to be stable using the first determination circuit unit 31 from becoming unnecessarily narrow. As described above, the effect of easily determining the region in which the reference voltage Vr is stable based on the drive voltage Vd is particularly useful when the BGR power supply voltage Vs is a voltage generated based on the circuit power supply voltage VDD.

[0055] According to the first embodiment, the control transistor 22 is a P-channel field-effect transistor. Therefore, unlike when the control transistor 22 is a bipolar transistor, no current flows from the first terminal, the source terminal 22s, to the drive terminal, the gate terminal 22g. Consequently, power consumption can be reduced more easily compared to when the control transistor 22 is a bipolar transistor. In addition, since no current flows from the gate terminal 22g to the control circuit section 21 and the first determination circuit section 31, the operation of each circuit section can be made more stable. Furthermore, since there is no need to provide a resistive element to convert current to voltage, the number of components in the semiconductor circuit 100 can be reduced.

[0056] (Second embodiment) Figure 4 is a circuit diagram showing the semiconductor circuit 200 of the second embodiment. In the following description, components similar to those in the embodiments described above may be denoted by the same reference numerals, and their descriptions may be omitted. The power supply unit 210 of the semiconductor circuit 200 shown in Figure 4 is an external power supply. The power supply unit 210 applies the BGR power supply voltage Vs to the control transistor 22. In the second embodiment, the BGR power supply voltage Vs output from the power supply unit 210 is a voltage that occurs independently of the circuit power supply voltage VDD. The power supply unit 210 is connected to ground 42. In the second embodiment, since the power supply unit 210 is an external power supply, the variation in the BGR power supply voltage Vs with respect to the circuit power supply voltage VDD can be reduced compared to the case where the power supply unit 210 is an internal power supply based on the circuit power supply voltage VDD. The other configurations of the semiconductor circuit 200 are the same as the other configurations of the semiconductor circuit 100 in the first embodiment.

[0057] (Third embodiment) Figure 5 is a circuit diagram showing a semiconductor circuit 300 of the third embodiment. In the following description, components similar to those in the embodiments described above may be omitted from explanation by using the same reference numerals. As shown in Figure 5, the control transistor 322 in the bandgap reference circuit section 320 of the semiconductor circuit 300 is a PNP type bipolar transistor. The control transistor 322 has an emitter terminal 322e, a collector terminal 322c, and a base terminal 322b. The emitter terminal 322e is connected to the wiring 11. The collector terminal 322c is connected to the reference voltage wiring 20a. A drive voltage Vd is applied to the base terminal 322b. A resistor element 322f for converting current to voltage is connected to the base terminal 322b. In the third embodiment, the emitter terminal 322e corresponds to the "first terminal," the collector terminal 322c corresponds to the "second terminal," and the base terminal 322b corresponds to the "drive terminal." Even if the control transistor 322 is a PNP bipolar transistor, the semiconductor circuit 300 operates in the same manner as the semiconductor circuit 100 in the first embodiment described above. The other configurations of the semiconductor circuit 300 are the same as the other configurations of the semiconductor circuit 100 in the first embodiment.

[0058] According to the third embodiment, the control transistor 322 is a PNP-type bipolar transistor. Therefore, the control transistor 322 can be made less expensive compared to using a P-channel type field-effect transistor as the control transistor 322.

[0059] According to at least one embodiment described above, the semiconductor circuit of the embodiment includes a bandgap reference circuit section that generates a reference voltage and a detection circuit section. The bandgap reference circuit section includes a control transistor positioned between a wiring to which a first power supply voltage is applied and a reference voltage wiring to which a reference voltage is applied, and a control circuit section that applies a drive voltage to the control transistor so that the reference voltage becomes a first predetermined value. The control transistor has a first terminal connected to the wiring to which the first power supply voltage is applied, a second terminal connected to the reference voltage wiring, and a drive terminal to which a drive voltage is applied. The control transistor turns ON when the voltage of the drive terminal, with the voltage of the first terminal as a reference, is a negative value and below a threshold. The detection circuit section includes a first determination circuit section that outputs a signal indicating whether or not the reference voltage is stable at a first predetermined value based on the drive voltage output from the control circuit section. This makes it easy to determine the region in which the reference voltage is stable based on the drive voltage output from the control circuit section.

[0060] The first determination circuit unit may have any configuration as long as it can determine whether the reference voltage is stable at a first predetermined value based on the drive voltage output from the control circuit unit. The first determination circuit unit may have a threshold value internally and determine whether the reference voltage is stable by comparing the threshold value with the drive voltage. In the determination method of the embodiment, the determination of whether the reference voltage is stable can be made in any way. In the determination method, a processor to which the drive voltage output from the control circuit unit is input may determine whether the reference voltage is stable based on the drive voltage. In this case, the processor may determine whether the reference voltage is stable by executing a program stored in the memory unit.

[0061] The first power supply voltage may be any voltage. The second power supply voltage may be any voltage. The first voltage may be any voltage as long as it is based on the reference voltage. The first voltage may be the same value as the reference voltage. The second voltage may be any voltage as long as it is based on the reference voltage. The second voltage may be the same value as the reference voltage. The first and second voltages may be different values ​​from each other. The third voltage may be any voltage as long as it is based on the second power supply voltage (circuit power supply voltage). The third voltage may be the same value as the second power supply voltage.

[0062] The second and third determination circuits may have any circuit configuration as long as they have their respective determination functions. The second and third determination circuits may not be provided. The detection circuit may be any detection circuit as long as it has the first determination circuit. The control circuit may have any configuration as long as it can apply a drive voltage to the control transistor so that the reference voltage becomes a first predetermined value. The control transistor may be any type of transistor as long as it is a transistor that turns ON when the voltage of the drive terminal, referenced to the voltage of the first terminal, is a negative value and below a threshold. The configuration of the bandgap reference circuit that generates the reference voltage is not limited to the embodiments described above. Any known bandgap reference circuit configuration can be adopted as the configuration of the bandgap reference circuit. The application of the semiconductor circuit is not particularly limited.

[0063] The semiconductor circuit and determination method of the embodiment include the following appended aspects. (Note 1) A bandgap reference circuit section that generates a reference voltage, Detection circuit section, Equipped with, The aforementioned bandgap reference circuit section is A control transistor is positioned between the wiring to which the first power supply voltage is applied and the reference voltage wiring to which the reference voltage is applied. A control circuit unit that applies a drive voltage to the control transistor so that the reference voltage becomes a first predetermined value, It has, The control transistor is A first terminal connected to the wiring to which the first power supply voltage is applied, A second terminal connected to the aforementioned reference voltage wiring, The drive terminal to which the aforementioned drive voltage is applied, The device has the following characteristics, and turns ON when the voltage of the drive terminal, with reference to the voltage of the first terminal, is a negative value and is below a threshold. The detection circuit unit is a semiconductor circuit having a first determination circuit unit that outputs a signal indicating whether or not the reference voltage is stable at a first predetermined value based on the drive voltage output from the control circuit unit. (Note 2) The first determination circuit receives the drive voltage and a first voltage based on the reference voltage as inputs. The first determination circuit unit outputs a signal indicating that the reference voltage is stable at a first predetermined value when the drive voltage is higher than the first voltage, as described in Appendix 1. (Note 3) The semiconductor circuit described in Appendix 2, wherein the first voltage is a resistive voltage divider of the reference voltage. (Note 4) The detection circuit unit includes a second determination circuit unit and a third determination circuit unit, and is capable of detecting when the second power supply voltage falls below a second predetermined value based on the reference voltage. The second determination circuit receives a second voltage based on the reference voltage and a third voltage based on the second power supply voltage. The third determination circuit receives the signal output from the first determination circuit and the signal output from the second determination circuit. The aforementioned third determination circuit section is: When predetermined conditions are met, a signal is output indicating that the second power supply voltage is equal to or greater than the second predetermined value. If the signal output from the first determination circuit is a signal indicating that the drive voltage is less than or equal to the first voltage, a signal indicating that the second power supply voltage is lower than the second predetermined value is output, and If the signal output from the second determination circuit is a signal indicating that the third voltage is less than or equal to the second voltage, a signal indicating that the second power supply voltage is lower than the second predetermined value is output. The semiconductor circuit according to Appendix 2 or Appendix 3, wherein the predetermined condition is satisfied when the signal output from the first determination circuit is a signal indicating that the drive voltage is higher than the first voltage, and the signal output from the second determination circuit is a signal indicating that the third voltage is higher than the second voltage. (Note 5) The second voltage is a resistive voltage divider of the reference voltage, The semiconductor circuit described in Appendix 4, wherein the third voltage is a resistive voltage divider of the second power supply voltage. (Note 6) The semiconductor circuit described in Appendix 4 or Appendix 5, wherein the first power supply voltage is a voltage generated based on the second power supply voltage. (Note 7) The control transistor is a P-channel type field-effect transistor, as described in any one of the semiconductor circuits described in Appendix 1 to Appendix 6. (Note 8) The control transistor is a PNP-type bipolar transistor, as described in any one of the semiconductor circuits described in Appendix 1 to Appendix 6. (Note 9) A determination method for determining a reference voltage generated by a bandgap reference circuit, The aforementioned bandgap reference circuit section is A control transistor is positioned between the wiring to which the first power supply voltage is applied and the reference voltage wiring to which the reference voltage is applied. A control circuit unit that applies a drive voltage to the control transistor so that the reference voltage becomes a first predetermined value, It has, The control transistor is A first terminal connected to the wiring to which the first power supply voltage is applied, A second terminal connected to the aforementioned reference voltage wiring, The drive terminal to which the aforementioned drive voltage is applied, The device has the following characteristics, and turns ON when the voltage of the drive terminal, with reference to the voltage of the first terminal, is a negative value and is below a threshold. The determination method includes determining whether the reference voltage is stable at the first predetermined value based on the drive voltage output from the control circuit unit. (Note 10) The determination method according to Appendix 9, which includes determining that the reference voltage is stable at the first predetermined value when the drive voltage is higher than the first voltage based on the reference voltage.

[0064] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0065] 11…Wiring, 20, 320…Bandgap reference circuit section, 20a…Reference voltage wiring, 21…Control circuit section, 22, 322…Control transistors, 22d…Drain terminal (second terminal), 22g…Gate terminal (drive terminal), 22s…Source terminal (first terminal), 30…Detection circuit section, 31…First determination circuit section, 32…Second determination circuit section, 33…Third determination circuit section, 100, 200, 300…Semiconductor circuit, 322b…Base terminal (drive terminal), 322c…Collector terminal (second terminal), 322e…Emitter terminal (first terminal), V1…First voltage, V2…Second voltage, V3…Third voltage, Vd…Drive voltage, VDD…Circuit power supply voltage (second power supply voltage), VDDa…Second predetermined value, Ve…First predetermined value, Vr…Reference voltage, Vs…BGR power supply voltage (first power supply voltage)

Claims

1. A bandgap reference circuit section that generates a reference voltage, Detection circuit section, Equipped with, The aforementioned bandgap reference circuit section is A control transistor is positioned between the wiring to which the first power supply voltage is applied and the reference voltage wiring to which the reference voltage is applied. A control circuit unit that applies a drive voltage to the control transistor so that the reference voltage becomes a first predetermined value, It has, The control transistor is A first terminal connected to the wiring to which the first power supply voltage is applied, A second terminal connected to the aforementioned reference voltage wiring, The drive terminal to which the aforementioned drive voltage is applied, It has the following characteristics, and turns ON when the voltage of the drive terminal, with respect to the voltage of the first terminal as a reference, is a negative value and is below a threshold. The detection circuit unit is a semiconductor circuit having a first determination circuit unit that outputs a signal indicating whether or not the reference voltage is stable at a first predetermined value based on the drive voltage output from the control circuit unit.

2. The first determination circuit receives the drive voltage and a first voltage based on the reference voltage as inputs. The semiconductor circuit according to claim 1, wherein the first determination circuit unit outputs a signal indicating that the reference voltage is stable at a first predetermined value when the drive voltage is higher than the first voltage.

3. The semiconductor circuit according to claim 2, wherein the first voltage is a resistive voltage divider of the reference voltage.

4. The detection circuit unit includes a second determination circuit unit and a third determination circuit unit, and is capable of detecting when the second power supply voltage falls below a second predetermined value based on the reference voltage. The second determination circuit receives a second voltage based on the reference voltage and a third voltage based on the second power supply voltage. The third determination circuit receives the signal output from the first determination circuit and the signal output from the second determination circuit. The aforementioned third determination circuit section is: When predetermined conditions are met, a signal is output indicating that the second power supply voltage is equal to or greater than the second predetermined value. If the signal output from the first determination circuit is a signal indicating that the drive voltage is less than or equal to the first voltage, a signal indicating that the second power supply voltage is lower than the second predetermined value is output, and If the signal output from the second determination circuit is a signal indicating that the third voltage is less than or equal to the second voltage, a signal indicating that the second power supply voltage is lower than the second predetermined value is output. The semiconductor circuit according to claim 2, wherein the predetermined condition is satisfied when the signal output from the first determination circuit is a signal indicating that the drive voltage is higher than the first voltage, and the signal output from the second determination circuit is a signal indicating that the third voltage is higher than the second voltage.

5. The second voltage is a resistive voltage divider of the reference voltage, The semiconductor circuit according to claim 4, wherein the third voltage is a resistive voltage divider of the second power supply voltage.

6. The semiconductor circuit according to claim 4, wherein the first power supply voltage is a voltage generated based on the second power supply voltage.

7. The semiconductor circuit according to any one of claims 1 to 6, wherein the control transistor is a P-channel type field-effect transistor.

8. The semiconductor circuit according to any one of claims 1 to 6, wherein the control transistor is a PNP-type bipolar transistor.

9. A determination method for determining a reference voltage generated by a bandgap reference circuit, The aforementioned bandgap reference circuit section is A control transistor is positioned between the wiring to which the first power supply voltage is applied and the reference voltage wiring to which the reference voltage is applied. A control circuit unit that applies a drive voltage to the control transistor so that the reference voltage becomes a first predetermined value, It has, The control transistor is A first terminal connected to the wiring to which the first power supply voltage is applied, A second terminal connected to the aforementioned reference voltage wiring, The drive terminal to which the aforementioned drive voltage is applied, It has the following characteristics, and turns ON when the voltage of the drive terminal, with respect to the voltage of the first terminal as a reference, is a negative value and is below a threshold. The determination method includes determining whether the reference voltage is stable at the first predetermined value based on the drive voltage output from the control circuit unit.

10. The determination method according to claim 9, further comprising determining that the reference voltage is stable at a first predetermined value when the drive voltage is higher than a first voltage based on the reference voltage.

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