Reference voltage generation circuit

Abstract

To provide a reference voltage generation circuit that is able to improve the accuracy of a reference potential without providing an operational amplifier.SOLUTION: A reference voltage generation circuit includes: a constant current source 10 that generates a constant current; a constant voltage forming circuit 20 that includes a Zener diode 21 to which current is supplied from the constant current source 10, and that forms a constant voltage, based on a Zener voltage Vz formed by the Zener diode 21; an Iptat generation circuit 40 that generates a PTAT current Iptat having a positive temperature characteristic with respect to an absolute temperature, based on the constant voltage without including an operational amplifier; and a temperature characteristic adjustment circuit 30 that includes a temperature characteristic adjustment resistor 31 through which the PTAT current Iptat generated by the Iptat generation circuit 40 flows. A voltage obtained by subtracting a voltage drop in the temperature characteristic adjustment circuit 30 when the PTAT current Iptat flows from the constant voltage is output as a reference potential VREF.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a reference voltage generating circuit. [Background technology]

[0002] To perform high-precision voltage measurements, a high-precision reference voltage generation circuit is required to be used as the reference potential for the A / D converter. However, there is a problem in that the accuracy deteriorates due to stress applied to the reference voltage generation circuit.

[0003] For this reason, the reference voltage generating circuit of Patent Document 1 generates a reference potential based on a current Iptat (proportional to absolute temperature: hereinafter referred to as PTAT current) having a positive temperature characteristic proportional to absolute temperature and a Zener diode, thereby reducing errors in the reference potential due to stress. Specifically, the PTAT current Iptat is generated, and a voltage generated based on the PTAT current Iptat is subtracted from the voltage generated by the Zener diode, thereby canceling out the temperature characteristic of the voltage generated by the Zener diode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2024-36956 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in Patent Document 1, the PTAT current Iptat is generated by a Brokaw cell circuit, which requires an operational amplifier and the like, and the number of elements used in the circuit configuration increases. This poses a problem in that the accuracy of the reference potential generated by the reference voltage generation circuit decreases due to variations between elements and noise generated during circuit operation.

[0006] An object of the present disclosure is to provide a reference voltage generating circuit that can improve the accuracy of the reference potential without including an operational amplifier. [Means for solving the problem]

[0007] A reference voltage generating circuit that outputs a reference potential (VREF) according to one aspect of the present disclosure includes: a constant current source (10) that generates a constant current; a constant voltage generating circuit (20) having a Zener diode (21) to which current is supplied from the constant current source, and generating a constant voltage based on a Zener voltage (Vz) generated by the Zener diode; a current generating circuit (40) that generates a PTAT current (Iptat) having a positive temperature characteristic with respect to absolute temperature based on the constant voltage without including an operational amplifier; a temperature characteristic adjustment circuit (30) including a temperature characteristic adjustment resistor (31) through which the PTAT current generated by the current generation circuit flows; A voltage obtained by subtracting the voltage drop in the temperature characteristic adjustment circuit when the PTAT current flows from the constant voltage is output as the reference potential.

[0008] In a reference voltage generating circuit configured in this manner, the PTAT current has a positive temperature characteristic. The constant voltage generated based on the Zener voltage also has a positive temperature characteristic due to the characteristics of the Zener diode. The reference potential is calculated by subtracting the voltage drop across the temperature characteristic adjustment resistor, which also has a positive temperature characteristic, from the constant voltage based on the Zener voltage, which has a positive temperature characteristic. This reduces the temperature characteristic of the reference potential, and by adjusting the resistance value of the temperature characteristic adjustment resistor, it is possible to further flatten the temperature characteristic of the reference potential.

[0009] Therefore, the temperature characteristics of the reference potential can be reduced without requiring an operational amplifier with a large number of elements, which reduces the effects of variations between elements and also reduces noise generated from elements during circuit operation, thereby improving the accuracy of the reference potential.

[0010] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a circuit diagram of a reference voltage generating circuit according to a first embodiment of the present disclosure. [Figure 2] 2 is a diagram showing a specific circuit configuration of the reference voltage generating circuit shown in FIG. 1. FIG. [Figure 3] FIG. 10 is a circuit diagram of a reference voltage generating circuit according to a second embodiment of the present disclosure. [Figure 4] FIG. 10 is a circuit diagram of a reference voltage generating circuit according to a modified example of the second embodiment. [Figure 5] FIG. 10 is a circuit diagram of a reference voltage generating circuit according to a third embodiment of the present disclosure. [Figure 6] FIG. 2 is a diagram illustrating an example of a circuit configuration of a trimming resistor. [Figure 7] FIG. 10 is a circuit diagram of a reference voltage generating circuit according to a fourth embodiment of the present disclosure. [Figure 8] FIG. 10 is a circuit diagram of a reference voltage generating circuit according to a fifth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following, including other embodiments described below, identical or equivalent parts will be denoted by the same reference numerals.

[0013] (First embodiment) A first embodiment of the present disclosure will be described below. First, the basic circuit configuration of a reference voltage generating circuit according to this embodiment will be described with reference to FIG.

[0014] The reference voltage generating circuit 1 shown in Fig. 1 is a circuit that generates a predetermined reference potential VREF based on a power supply voltage VDD applied via a power supply line 2. The power supply voltage VDD may be any voltage that can be used to generate the reference potential VREF, that is, a voltage higher than the reference potential VREF, and may be, for example, a voltage higher than the 5V generated by a 5V power supply, which is a general constant voltage source. Here, the power supply voltage VDD is assumed to be a voltage of about 9 to 14V.

[0015] The reference voltage generating circuit 1 includes a constant current source 10, a constant voltage forming circuit 20, a temperature characteristic adjusting circuit 30, and an Iptat generating circuit 40.

[0016] In this embodiment, the constant current source 10 is composed of a first constant current source 11 and a second constant current source 12, and generates a constant current based on the power supply voltage VDD from the power supply line 2. The first constant current source 11 generates a first constant current I1 for supplying current to the constant voltage generating circuit 20, the temperature characteristic adjusting circuit 30, and the Iptat generating circuit 40. The second constant current source 12 generates a second constant current I2 for supplying current to the Iptat generating circuit 40. The first constant current I1 and the second constant current I2 may have the same current value, but in this example, the first constant current I1 is set to a relatively large current value, and the second constant current I2 is set to a smaller current value than the first constant current I1. For example, the first constant current I1 is set to approximately 100 to 200 μA, and the second constant current I2 is set to approximately 10 μA, which is approximately 1 / 10 of the first constant current I1.

[0017] The constant voltage generating circuit 20 generates a constant voltage to be applied to the temperature characteristic adjustment circuit 30 and the Iptat generating circuit 40. In this embodiment, the constant voltage generating circuit 20 is configured only with a Zener diode 21, and the Zener voltage Vz generated by the Zener diode 21 is used as the constant voltage. Specifically, a first constant current source 11 and the Zener diode 21 are connected in series between a power supply line 2 and a GND (ground) line 3, with the cathode of the Zener diode 21 connected to the first constant current source 11 and the anode connected to the GND (ground) line 3. Therefore, the constant voltage generating circuit 20 generates the breakdown voltage of the Zener diode 21, i.e., the Zener voltage Vz, as a constant voltage at the connection point between the Zener diode 21 and the first constant current source 11. The constant voltage is set to a voltage higher than the reference potential VREF, for example, a voltage of approximately 6 to 7 V.

[0018] The temperature characteristic adjustment circuit 30 generates a reference potential VREF together with the Iptat generation circuit 40 based on the flow of the PTAT current Iptat generated by the Iptat generation circuit 40. Here, the temperature characteristic adjustment circuit 30 is configured by a temperature characteristic adjustment resistor 31, one end of which is connected to the cathode of the Zener diode 21 and the other end of which is connected to the Iptat generation circuit 40.

[0019] The Iptat generation circuit 40 corresponds to a current generation circuit, and generates a PTAT current Iptat, which is a current having a positive temperature characteristic proportional to absolute temperature, without using an operational amplifier, thereby generating a reference potential VREF. Specifically, the Iptat generation circuit 40 generates the PTAT current Iptat based on a first constant current I1 and a second constant current I2, thereby generating a reference potential VREF as a potential between the temperature characteristic adjustment circuit 30 and the Iptat generation circuit 40. The reference potential VREF is a value obtained by subtracting the voltage drop of the temperature characteristic adjustment circuit 30 from the constant voltage generated by the constant voltage generation circuit 20. Therefore, the temperature characteristic of the constant voltage generation circuit 20 is canceled out based on the temperature characteristic of the temperature characteristic adjustment circuit 30, making it possible to flatten the temperature characteristic.

[0020] FIG. 2 shows an example in which the Iptat generating circuit 40 has a Widlar type circuit configuration, and the reason why the temperature characteristic of the reference potential VREF becomes flat will be described along with the operation of the reference voltage generating circuit according to this embodiment.

[0021] 2, in this embodiment, the Iptat generation circuit 40 is configured by a first transistor 41, a second transistor 42, and an Iptat generation resistor 43. The first transistor 41 and the second transistor 42 are a pair of transistors. Of these, the first transistor 41 corresponds to one transistor, and the second transistor 42 corresponds to the other transistor.

[0022] The first transistor 41 and the second transistor 42 are configured as NPN bipolar transistors. The current densities are made different by, for example, making the element area of ​​the second transistor 42 different from that of the first transistor 41, and the element area of ​​the second transistor 42 is designed to be N times (where N is a positive value) that of the first transistor 41. Specifically, the first transistor 41 and the second transistor 42 have their bases connected in common to the second constant current source 12. The collector of the first transistor 41 is connected to the second constant current source 12, and the collector of the second transistor 42 is connected to the temperature characteristic adjustment circuit 30. The emitter of the first transistor 41 is connected to the GND line 3, and the emitter of the second transistor 42 is connected to the GND line 3 via an Iptat generation resistor 43. By connecting the Iptat generation resistor 43 between the emitter of the second transistor 42 and the GND line 3, a potential difference ΔVbe corresponding to a voltage drop is generated across the Iptat generation resistor 43.

[0023] The reference voltage generating circuit 1 configured as above operates as follows.

[0024] First, a constant voltage is generated in the constant voltage generating circuit 20 based on the current supplied from the first constant current source 11. In this embodiment, the constant voltage is the Zener voltage Vz. Based on the current supplied from the second constant current source 12, the first transistor 41 and the second transistor 42 are driven, and a current flows between the collector and emitter of the first transistor 41 and the second transistor 42. The current flowing between the collector and emitter of the second transistor 42 is the PTAT current Iptat, which also flows through the temperature characteristic adjustment circuit 30 and the Iptat generation resistor 43. The difference in current density between the first transistor 41 and the second transistor 42 generates a potential difference ΔVbe across the Iptat generation resistor 43, and this potential difference ΔVbe flows through the Iptat generation resistor 43, causing the PTAT current Iptat to flow.

[0025] At this time, the potential difference ΔVbe is the base-emitter voltage V of the first transistor 41. BE1 and the base-emitter voltage V of the second transistor 42 BE2 The potential difference ΔVbe is expressed as the difference between the first transistor 41 and the second transistor 42. Furthermore, if the Boltzmann multiplier is k, the absolute temperature of the reference voltage generating circuit 1 is T, the elementary charge is q, the collector current is Ic, and the saturation current is Is, the potential difference ΔVbe is expressed by Equation 1. Note that for simplicity, the current amplification factor is set to ∞. Furthermore, regarding the subscripts attached to the collector current Ic and the saturation current Is, "1" indicates the first transistor 41, and "2" indicates the second transistor 41.

[0026]

number

[0027]

number

[0028]

number

[0029] As described above, the PTAT current Iptat has a positive temperature characteristic as expressed by Equation 3. The Zener voltage Vz also has a positive temperature characteristic based on the characteristics of the Zener diode 21. As shown in Equation 2, the reference potential VREF is calculated by subtracting the voltage drop across the temperature characteristic adjustment resistor 31, which also has a positive temperature characteristic, from the Zener voltage Vz(T), which has a positive temperature characteristic. Therefore, the temperature characteristic of the reference potential VREF can be reduced, and by adjusting the resistance value R1 of the temperature characteristic adjustment resistor 31, it is possible to make the temperature characteristic of the reference potential VREF even flatter.

[0030] Therefore, the temperature characteristics of the reference potential VREF can be reduced without requiring a configuration with a large number of elements such as operational amplifiers. This reduces the effects of variations between elements, reduces noise generated from elements during circuit operation, and improves the accuracy of the reference potential VREF.

[0031] (Second embodiment) A second embodiment of the present disclosure will be described. This embodiment is different from the first embodiment in that the configuration of the Iptat generation circuit 40 is changed, but the rest is the same as the first embodiment, so only the parts that are different from the first embodiment will be described.

[0032] 3, the Iptat generation circuit 40 of this embodiment includes a transistor group having a third transistor 44 and a fourth transistor 45 in addition to a first transistor 41 and a second transistor 42, which are cross-coupled. The PTAT current Iptat flows to an Iptat generation resistor 43 via the transistor group.

[0033] The third transistor 44 and the fourth transistor 45 are configured by NPN-type bipolar transistors. The current densities are made different by, for example, making the element area of ​​the fourth transistor 45 different from that of the third transistor 44, and the element area of ​​the third transistor 44 is designed to be N times that of the fourth transistor 45. Here, N times is the same as the element area of ​​the second transistor 42 N times that of the first transistor 41. Specifically, the third transistor 44 and the fourth transistor 45 have their bases commonly connected to the second constant current source 12. The collector of the third transistor 44 is connected to the second constant current source 12, and the collector of the fourth transistor 45 is connected to the temperature characteristic adjustment circuit 30.

[0034] The first transistor 41 and the second transistor 42 are basically configured in the same manner as in the first embodiment, but the connections of the bases and collectors of the first transistor 41 and the second transistor 42 are different. That is, the base of the first transistor 41 is connected to the emitter of the fourth transistor 45, and the collector is connected to the emitter of the third transistor 44. Moreover, the base of the second transistor 42 is connected to the emitter of the third transistor 44, and the collector is connected to the emitter of the fourth transistor 45.

[0035] In this way, in addition to the first transistor 41 and the second transistor 42, the third transistor 44 and the fourth transistor 45 are provided, and these are cross-coupled to form a two-stage bipolar transistor configuration. With this circuit configuration, the potential difference ΔVbe between both ends of the Iptat generating resistor 43 becomes twice that in the first embodiment, but since the noise generated from the elements is uncorrelated, 1 / 2 Therefore, it is possible to achieve substantial noise reduction.

[0036] (Modification of the second embodiment) In the second embodiment, two stages of bipolar transistors are used in a cross-coupled connection, but it is also possible to add more stages of bipolar transistors to form three or more stages. For example, as shown in FIG. 4, a fifth transistor 46 and a sixth transistor 47 can be further provided to form a three-stage circuit.

[0037] In this case, the fifth transistor 46 and the sixth transistor 47 are also configured as NPN-type bipolar transistors. The current density is made different by, for example, making the element area of ​​the sixth transistor 47 different from that of the fifth transistor 46, and the element area of ​​the sixth transistor 47 is designed to be N times larger than that of the fifth transistor 46. The bases of the fifth transistor 46 and the sixth transistor 47 are connected in common to the second constant current source 12, the collector of the fifth transistor 46 is connected to the second constant current source 12, and the collector of the sixth transistor 47 is connected to the temperature characteristic adjustment circuit 30. The base of the third transistor 44 is connected to the emitter of the sixth transistor 47, and the collector is connected to the emitter of the fifth transistor 46. Furthermore, the base of the fourth transistor 45 is connected to the emitter of the fifth transistor 46, and the collector is connected to the emitter of the sixth transistor 47.

[0038] In this way, the potential difference ΔVbe across the Iptat generation resistor 43 can be increased by the number of bipolar transistor stages, that is, by the integrated value of the differences in base-emitter voltage between one transistor and the other transistor in each pair. Furthermore, since the potential difference ΔVbe across the Iptat generation resistor 43 can be increased while suppressing an increase in noise, it is possible to achieve more substantial noise reduction.

[0039] Although the case where the number of bipolar transistor stages is three has been described here, the above-mentioned effect can also be achieved when the transistor group includes multiple pairs of transistors. That is, a pair of transistors arranged in order from the GND line 3 side is considered to be one set, and the pair of transistors in each set is set to have the following relationship. Note that, of the pair of transistors in each set, the one through which the main collector-emitter current flows based on the current supply from the first constant current source 11 is called one transistor, and the one through which the main collector-emitter current flows based on the current supply from the second constant current source 12 is called the other transistor. Furthermore, when there are m stages (where m is a natural number greater than or equal to 2), the sets, starting from the GND line 3 side that is the lowest side, are called the first set, the second set, ..., the mth set.

[0040] That is, for odd-numbered pairs, the element area of ​​one transistor is N times larger than the element area of ​​the other transistor. Conversely, for even-numbered pairs counting from the GND line 3 side, the element area of ​​one transistor is N times larger than the element area of ​​the other transistor. Furthermore, for the first pair, which is the lowest side, the emitter of one transistor is connected to the GND line 3, and the emitter of the other transistor is connected to Iptat generating resistor 43. The base of one transistor in the first pair and the collector of the other transistor are connected to the emitter of the other transistor in the next pair, the second pair. Furthermore, the collector of one transistor in the first pair and the base of the other transistor are connected to the emitter of one transistor in the second pair.

[0041] Furthermore, for the intermediate sets from the 1st set to the mth set, the emitter of one transistor is connected to the collector of one transistor and the base of the other transistor in the previous set. Similarly, the emitter of the other transistor in the intermediate sets is connected to the base of one transistor and the collector of the other transistor in the previous set. Then, for the mth set, which is the highest set, the collector and base of one transistor and the base of the other transistor are connected to the second constant current source 12, and the collector of the other transistor is connected to the temperature characteristic adjustment circuit 30. In this way, by configuring the Iptat generation circuit 40 by cross-coupling multiple stages of transistors, more substantial noise reduction can be achieved.

[0042] (Third embodiment) A third embodiment of the present disclosure will be described. This embodiment is different from the first and second embodiments in that it is provided with a function for adjusting the voltage value of the reference potential VREF, and is otherwise similar to the first and second embodiments, so only the differences from the first and second embodiments will be described.

[0043] 5, the constant voltage forming circuit 20 of this embodiment is configured to include a first voltage dividing resistor 22 and a second voltage dividing resistor 23 in addition to a Zener diode 21. The first voltage dividing resistor 22 and the second voltage dividing resistor 23 are connected in parallel to the Zener diode 21. The first voltage dividing resistor 22 and the second voltage dividing resistor 23 are connected in series between the first constant current source 11 and the GND line 3. By resistively dividing the Zener voltage Vz using the first voltage dividing resistor 22 and the second voltage dividing resistor 23, a constant voltage lower than the Zener voltage Vz is formed, making it possible to lower the output voltage of the reference potential VREF.

[0044] As in the first embodiment, when the reference potential VREF is generated by dividing the Zener voltage Vz as a constant voltage using the temperature characteristic adjustment resistor 31 and the Iptat generation resistor 43, the output voltage of the reference potential VREF may become a desired voltage value, for example, 5 V or more. If the voltage exceeds the desired voltage value, it may go outside the operating range of subsequent circuits that operate based on the reference potential VREF.

[0045] On the other hand, if the first voltage-dividing resistor 22 and the second voltage-dividing resistor 23 are connected in parallel to the Zener diode 21, the constant voltage can be a voltage based on the Zener voltage Vz rather than the Zener voltage Vz, resulting in a voltage obtained by resistively dividing the Zener voltage Vz. For example, if the resistance value of the first voltage-dividing resistor 22 is RA and the resistance value of the second voltage-dividing resistor 23 is RB, the constant voltage can be Vz × RB / (RA + RB), and the reference potential VREF can be generated based on this constant voltage. This prevents the output voltage of the reference potential VREF from exceeding a desired voltage value, ensuring proper operation of downstream circuits that operate based on the reference potential VREF.

[0046] Furthermore, in this embodiment, the temperature characteristic adjustment circuit 30 includes a trimming resistor 32 in addition to the temperature characteristic adjustment resistor 31, making it possible to finely adjust the temperature characteristic of the output voltage of the reference potential VREF.

[0047] 6, if the high-side terminal of the trimming resistor 32 is designated as a first terminal 32a and the low-side terminal is designated as a second terminal 32b, a plurality of resistors R are connected in series between the first terminal 32a and the second terminal 32b. The low-side terminal of each resistor R is connected to an output terminal 32c via switches SW1 to SW4, and the output voltage of this output terminal 32c is set as a reference potential VREF. The switches SW1 to SW4 are configured, for example, by MOSFETs or the like.

[0048] With this configuration, the resistance value of the trimming resistor 32 can be set by turning on any of the switches SW1 to SW4. For example, suppose that switches SW1 and SW4 are turned on. In this case, the PTAT current Iptat flows only through the resistor R closest to the first terminal 32a. The PTAT current Iptat does not flow through the other resistors R because it is bypassed via switches SW1 and SW4. Therefore, the resistance value R3 of the trimming resistor 32 is set to the resistance value of one resistor R. In this way, providing the trimming resistor 32 in the temperature characteristic adjustment circuit 30 enables fine adjustment of the temperature characteristic of the reference potential VREF. Specifically, in the reference voltage generation circuit 1 of this embodiment, the reference potential VREF is expressed as shown in Equation 4.

[0049]

number

[0050] Therefore, by adjusting the resistance value R3 of the trimming resistor 32 by controlling the switches SW1 to SW4, the temperature characteristic of the reference potential VREF can be finely adjusted, and the temperature characteristic of the output voltage can be set to any desired value.

[0051] (Fourth embodiment) A fourth embodiment of the present disclosure will be described. This embodiment is different from the first to third embodiments in the configuration of the Iptat generation circuit 40, but is otherwise similar to the first to third embodiments, so only the parts that differ from the first to third embodiments will be described. Note that, here, an example will be given in which the circuit configuration of this embodiment is applied to the circuit configuration of the first embodiment, but it can also be applied to the circuit configurations of the second and third embodiments.

[0052] 7, the reference voltage generating circuit 1 of this embodiment includes a fluctuation suppressing resistor 48 between the second constant current source 12 and the collector of the first transistor 41 in the Iptat generating circuit 40, that is, between the base and collector of the first transistor 41. In other words, the base of the first transistor 41 is connected to the second constant current source 12, while the collector is connected to the second constant current source 12 via the fluctuation suppressing resistor 48.

[0053] In this way, by adding the fluctuation suppressing resistor 48, fluctuations in the collector voltage are suppressed in response to fluctuations in the base voltage of the first transistor 41. This makes it possible to reduce noise caused by fluctuations in the collector voltage.

[0054] (Fifth embodiment) A fifth embodiment of the present disclosure will be described. This embodiment is different from the first to fourth embodiments in the configuration of the constant current source 10, but is otherwise similar to the first to fourth embodiments, so only the differences from the first to fourth embodiments will be described. Note that, here, an example will be given in which the circuit configuration of this embodiment is applied to the circuit configuration of the first embodiment, but it can also be applied to the circuit configurations of the second to fourth embodiments.

[0055] 8, in the reference voltage generating circuit 1 of this embodiment, the constant current source 10 is configured with only one first constant current source 11. The single constant current source 10 generates a first constant current I1 that serves as a current to the constant voltage forming circuit 20 and a PTAT current Iptat to the temperature characteristic adjustment circuit 30, the second transistor 42, and the Iptat generating resistor 43, and a second constant current I2 that is supplied to the first transistor 41. A current adjustment resistor 50 is provided between the constant current source 10 and the collector of the first transistor 41, and the second constant current I2 that is supplied to the first transistor 41 can be adjusted to an arbitrary current by the current adjustment resistor 50.

[0056] In this way, the reference voltage generating circuit 1 can be configured using only one constant current source 10. In this case, the number of noise sources is reduced by the single constant current source 10, making it possible to further reduce noise. Furthermore, the constant voltage generating circuit 20 generates a constant voltage based on the Zener voltage Vz generated by the Zener diode 21, and this constant voltage is applied to the current adjusting resistor 50, the first transistor 41, etc. Therefore, due to the rectifying effect of the Zener diode 21, noise from not only the second transistor 42 but also the first transistor 41 is reduced, thereby enabling further noise reduction.

[0057] (Other embodiments) Although the present disclosure has been described based on the above-described embodiment, it is not limited to the embodiment and encompasses various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0058] For example, the numbers of the various resistors shown in the first to fifth embodiments, the number of Zener diodes 21, etc. can be changed as appropriate depending on the design of the circuit to which the reference voltage generating circuit 1 is applied. When the number of resistors R included in the trimming resistor 32 described in the third embodiment is changed, the number of switches SW1 to SW4 can be increased accordingly. Furthermore, the resistors R may have the same resistance value, but they may have different resistance values, for example, the resistance value of one resistor may be set to two, four, or eight times the resistance value of the other resistors, thereby broadening the range of trimmable resistance values.

[0059] In the third embodiment, the constant voltage generating circuit 20 is configured to generate a constant voltage by resistive voltage division using the first voltage dividing resistor 22 and the second voltage dividing resistor 23, and is also configured to include the trimming resistor 32 to finely adjust the resistance value of the temperature characteristic adjusting circuit 30. However, a configuration in which only one of these resistors is included may also be used.

[0060] Furthermore, in each of the above embodiments, the first constant current source 11 and the second constant current source 12 share a common power supply voltage VDD as their power supply, but different power supply voltages may also be used.

[0061] Furthermore, although the third to fifth embodiments have been shown to be applicable to each of the embodiments including the first and second embodiments, they are of course also applicable to a modified example of the second embodiment.

[0062] (Aspects of the present disclosure) The present disclosure described above can be understood from the following viewpoints, for example. [First viewpoint] A reference voltage generating circuit that outputs a reference potential (VREF), a constant current source (10) that generates a constant current; a constant voltage generating circuit (20) having a Zener diode (21) to which current is supplied from the constant current source, and generating a constant voltage based on a Zener voltage (Vz) generated by the Zener diode; a current generating circuit (40) that generates a PTAT current (Iptat) having a positive temperature characteristic with respect to absolute temperature based on the constant voltage without including an operational amplifier; a temperature characteristic adjustment circuit (30) including a temperature characteristic adjustment resistor (31) through which the PTAT current generated by the current generation circuit flows; a reference voltage generating circuit that outputs, as the reference potential, a voltage obtained by subtracting from the constant voltage a voltage drop in the temperature characteristic adjusting circuit when the PTAT current flows; [Second perspective] the current generating circuit includes one transistor (41), another transistor (42) having a current density different from that of the one transistor, and a current adjusting resistor (43) through which the PTAT current flows; a current is supplied from the constant current source between the collector and the emitter of the one transistor; the collector of the other transistor is connected to the temperature characteristic adjustment circuit, the emitter is connected to the current adjustment resistor, and the base is connected to the collector of the one transistor, and the PTAT current flows between the temperature characteristic adjustment circuit and the collector-emitter of the other transistor and to the current adjustment resistor based on the current supply from the constant current source; The reference voltage generating circuit according to the first aspect, wherein a voltage (ΔVbe) that is a difference between the base-emitter voltage (VBE1) of the one transistor and the base-emitter voltage (VBE2) of the other transistor is generated as a potential difference across the current adjusting resistor. [Third Perspective] the current generating circuit includes a transistor group in which a plurality of pairs of one transistor (41, 44, 46) and another transistor (42, 45, 47) having a different current density from the one transistor are cross-coupled and connected, and a current adjusting resistor (43) through which the PTAT current flows; a current is supplied from the constant current source between the collector and the emitter of each of the plurality of one-type transistors included in the transistor group; the collector of the highest-side transistor among the plurality of other transistors included in the transistor group is connected to the temperature characteristic adjustment circuit, and the emitter of the lowest-side transistor is connected to the current adjustment resistor, and the PTAT current flows between the temperature characteristic adjustment circuit and the collectors and emitters of the plurality of other transistors and to the current adjustment resistor based on the current supply from the constant current source; The reference voltage generating circuit according to a first aspect, wherein a voltage (ΔVbe) obtained by integrating the difference between the base-emitter voltage (VBE1) of one of the transistors in each of the plurality of pairs and the base-emitter voltage (VBE2) of the other of the transistors is generated as a potential difference across the current adjusting resistor. [Fourth viewpoint] The reference voltage generating circuit according to the second or third aspect, further comprising a fluctuation suppressing resistor (48) provided between the base and collector of the one of the transistors for suppressing fluctuations in the collector voltage in response to fluctuations in the base voltage of the one of the transistors. [Fifth viewpoint] The constant current source includes a first constant current source (11) and a second constant current source (12), a current based on a first constant current (I1) generated by the first constant current source is supplied to the Zener diode, thereby forming the constant voltage, and is also supplied to the temperature characteristic adjustment circuit, between the collector and emitter of the other transistor, and to the current adjustment resistor, thereby generating the PTAT current; A reference voltage generating circuit according to any one of the second to fourth aspects, wherein a second constant current (I2) smaller than the first constant current generated by the second constant current source is supplied between the collector and emitter of the one of the transistors. [Sixth viewpoint] the constant current source is composed of only one a current adjusting resistor (50) is provided between the constant current source and the one of the transistors; a current based on the constant current generated by the constant current source is supplied to the Zener diode to form the constant voltage, and the PTAT current is generated by supplying the current to the temperature characteristic adjustment circuit, between the collector and emitter of the other transistor, and to the current adjustment resistor; The reference voltage generating circuit according to any one of the second to fourth aspects, wherein a current based on the constant current generated by the constant current source is supplied between the collector and emitter of the other transistor via the current adjusting resistor. [Seventh viewpoint] The temperature characteristic adjustment circuit is provided with a trimming resistor (32) in addition to the temperature characteristic adjustment resistor, The reference voltage generating circuit according to any one of the first to sixth aspects, wherein a voltage drop in the temperature characteristic adjustment circuit when the PTAT current flows through the temperature characteristic adjustment resistor and the trimming resistor is subtracted from the constant voltage, and the voltage is output as the reference potential. [Eighth viewpoint] The reference voltage generation circuit according to any one of the first to sixth aspects, wherein the constant voltage forming circuit has a first voltage dividing resistor (22) and a second voltage dividing resistor (23) connected in parallel to the Zener diode, and forms a voltage divided by the first voltage dividing resistor and the second voltage dividing resistor as the constant voltage. [Explanation of symbols]

[0063] 1...reference voltage generating circuit, 2...power supply line, 3...GND line, 10...constant current source, 11...first constant current source, 12...second constant current source, 20...constant voltage forming circuit, 21...Zener diode, 22...first voltage dividing resistor, 23...second voltage dividing resistor, 30...temperature characteristic adjusting circuit, 31...temperature characteristic adjusting resistor, 32...trimming resistor, 32a...first terminal, 32b...second terminal, 32c...output terminal, 40...Iptat generating circuit, 41...first transistor, 42...second transistor, 43...Iptat generating resistor, 44...third transistor, 45...fourth transistor, 46...fifth transistor, 47...sixth transistor, 48...fluctuation suppressing resistor, 50...current adjusting resistor, I1...first constant current, I2...second constant current, Iptat...PTAT current

Claims

1. A reference voltage generating circuit that outputs a reference potential (VREF), a constant current source (10) that generates a constant current; a constant voltage generating circuit (20) having a Zener diode (21) to which current is supplied from the constant current source, and generating a constant voltage based on a Zener voltage (Vz) generated by the Zener diode; a current generating circuit (40) that generates a PTAT current (Iptat) having a positive temperature characteristic with respect to absolute temperature based on the constant voltage without including an operational amplifier; a temperature characteristic adjustment circuit (30) including a temperature characteristic adjustment resistor (31) through which the PTAT current generated by the current generation circuit flows; a reference voltage generating circuit that outputs, as the reference potential, a voltage obtained by subtracting from the constant voltage a voltage drop in the temperature characteristic adjusting circuit when the PTAT current flows;

2. The current generating circuit includes one transistor (41), another transistor (42) having a current density different from that of the one transistor, and a current adjusting resistor (43) through which the PTAT current flows; A current is supplied from the constant current source between the collector and the emitter of the one transistor, the collector of the other transistor is connected to the temperature characteristic adjustment circuit, the emitter is connected to the current adjustment resistor, and the base is connected to the collector of the one transistor, and the PTAT current flows between the temperature characteristic adjustment circuit and the collector-emitter of the other transistor and to the current adjustment resistor based on the current supply from the constant current source; 2. The reference voltage generating circuit according to claim 1, wherein a voltage (ΔVbe) that is a difference between the base-emitter voltage (VBE1) of the one transistor and the base-emitter voltage (VBE2) of the other transistor is generated as a potential difference across the current adjusting resistor.

3. The current generating circuit includes a transistor group in which a plurality of pairs of transistors (41, 44, 46) are cross-coupled and connected to each other, the pair consisting of a transistor (42, 45, 47) having a different current density from the one transistor, and a current adjusting resistor (43) through which the PTAT current flows; a current is supplied from the constant current source between the collector and the emitter of each of the plurality of one-type transistors included in the transistor group; the collector of the highest-side transistor among the plurality of other transistors included in the transistor group is connected to the temperature characteristic adjustment circuit, and the emitter of the lowest-side transistor is connected to the current adjustment resistor, and the PTAT current is caused to flow between the collector and emitter of the temperature characteristic adjustment circuit and the plurality of other transistors and to the current adjustment resistor based on the current supply from the constant current source; 2. The reference voltage generating circuit according to claim 1, wherein a voltage (ΔVbe) obtained by integrating the difference between the base-emitter voltage (VBE1) of one of the transistors in each of the plurality of pairs and the base-emitter voltage (VBE2) of the other transistor is generated as a potential difference across the current adjusting resistor.

4. 3. The reference voltage generating circuit according to claim 2, further comprising a variation suppressing resistor (48) disposed between the base and collector of said one of the transistors for suppressing a variation in the collector voltage in response to a variation in the base voltage of said one of the transistors.

5. The constant current source includes a first constant current source (11) and a second constant current source (12), a current based on a first constant current (I1) generated by the first constant current source is supplied to the Zener diode, thereby forming the constant voltage; and a current is supplied to the temperature characteristic adjustment circuit, between the collector and the emitter of the other transistor, and to the current adjustment resistor, thereby generating the PTAT current; 5. The reference voltage generating circuit according to claim 2, wherein a second constant current (I2) smaller than the first constant current generated by the second constant current source is supplied between the collector and emitter of the one of the transistors.

6. the constant current source is composed of only one a current adjusting resistor (50) is provided between the constant current source and the one of the transistors; a current based on the constant current generated by the constant current source is supplied to the Zener diode to form the constant voltage, and the PTAT current is generated by supplying the current to the temperature characteristic adjustment circuit, between the collector and the emitter of the other transistor, and to the current adjustment resistor; 5. The reference voltage generating circuit according to claim 2, wherein a current based on the constant current generated by said constant current source is supplied between the collector and emitter of said other transistor via said current adjusting resistor.

7. The temperature characteristic adjustment circuit is provided with a trimming resistor (32) in addition to the temperature characteristic adjustment resistor, 5. The reference voltage generating circuit according to claim 1, wherein a voltage obtained by subtracting a voltage drop caused when the PTAT current flows through the temperature characteristic adjustment resistor and the trimming resistor from the constant voltage is output as the reference potential, as a voltage drop in the temperature characteristic adjustment circuit when the PTAT current flows.

8. 5. The reference voltage generating circuit according to claim 1, wherein the constant voltage generating circuit has a first voltage dividing resistor (22) and a second voltage dividing resistor (23) connected in parallel to the Zener diode, and generates a voltage divided by the first voltage dividing resistor and the second voltage dividing resistor as the constant voltage.

Images