JP2009117946A - Electronic component circuit with input circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic component circuit with an input circuit which is a simple circuit with a small number of components even though input voltage input to the input terminal of an electronic component is limited. <P>SOLUTION: The electronic component circuit 10 with an input circuit is provided with an electronic component 2 having an input terminal INA, etc., an input circuit 4A, etc., and an input voltage limiting circuit 9. The input voltage limiting circuit 9 includes a plurality of diodes 6A, 6B and 6C placed among a constant voltage circuit 3 for making a constant voltage node 5 a prescribed constant voltage Vc, the constant node 5 and the input circuit 4A, and connecting an anode 6Aa to the input circuit 4A, and a cathode 6Ac to the constant voltage node 5, respectively, wherein constant voltage Vc in the constant voltage node 5 is made smaller than a value obtained by subtracting a forward voltage drop Vf from maximum allowable voltage Vmax (Vc<Vmax-Vf) when the forward voltage drop of the diodes 6A, 6B and 6C is denoted by Vf. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electronic component circuit with an input circuit provided with an input circuit that transmits an input signal to an input terminal of the electronic component.

For example, in an electronic component such as a CPU, the maximum input voltage Vmax at the input terminal of the electronic component is often equal to a power supply voltage (for example, 5 V) for driving the electronic component.
On the other hand, in order to prevent the magnitude of the input signal input to the input terminal due to noise or the like from exceeding the maximum input voltage Vmax, the input voltage is limited to the input circuit that transmits the input signal to the component input terminal. A circuit is attached. As this input voltage limiting circuit, a circuit in which a diode having a cathode on the power supply voltage side is interposed between the input circuit and the power supply voltage is known.

  Further, it may be possible to provide a voltage dividing circuit using two resistors closer to the input terminal of the electronic component than the anode of the diode. In this way, the voltage divider circuit is provided only by using a diode, and the input voltage input to the input terminal is a maximum of the power supply voltage + the forward voltage drop Vf (for example, 5 + Vf) of the diode. Thus, the maximum input voltage Vmax (= power supply voltage) is exceeded. This is because the input voltage input to the component input terminal is further reduced by using a voltage dividing circuit (below the maximum input voltage Vmax (= power supply voltage)).

However, in this case, when a plurality of component input terminals are provided, a voltage dividing circuit (two resistance elements) is required in addition to the diode for each component input terminal, resulting in an increase in cost. In addition, the circuit becomes complicated.
The present invention has been made in view of such problems, and has an input circuit with an input circuit that is a simple circuit with a reduced number of parts while limiting the input voltage input to the input terminal of the electronic component. I will provide a.

  The solution includes one or a plurality of electronic components having a plurality of component input terminals, and each having a circuit input terminal, connected to each of the component input terminals, and receiving a signal input to the circuit input terminal. A plurality of input circuits that are respectively input to the component input terminals as signals, and an input voltage Vi of the input signal that is input to each of the component input terminals is less than or equal to a maximum input voltage Vmax that can be input to the component input terminals. An input voltage limiting circuit that regulates the constant voltage node to a predetermined constant voltage Vc, interposed between the constant voltage node and the plurality of input circuits, and an anode to the input circuit, A plurality of diodes each having a cathode connected to the constant voltage node, and when the forward voltage drop of the diode is Vf, the constant voltage at the constant voltage node The vc, an input circuit with an electronic component circuit comprising formed by less than the value obtained by subtracting the forward voltage drop Vf from the maximum allowed voltage Vmax and (vc <Vmax-Vf) Input voltage limiting circuit.

In the electronic component circuit with an input circuit according to the present invention, the input voltage limiting circuit includes a diode and a constant voltage circuit in which the generated constant voltage Vc is smaller than a value obtained by subtracting the forward voltage drop Vf from the maximum allowable voltage Vmax. .
Therefore, in the electronic component circuit with an input circuit of the present invention, as described above, the input signal input to each component input terminal of the electronic component can be maximized without further providing a voltage dividing circuit in each input circuit. The input voltage Vmax or less can be regulated, and an inexpensive and simple circuit configuration can be obtained.

  The constant voltage circuit may be a constant voltage circuit configured by providing a constant voltage source for generating a constant voltage in an electronic component circuit with an input circuit, or connected to an external constant voltage source. It may be a circuit.

  The electronic component circuit with an input circuit described above may be an electronic component circuit with an input circuit provided with an inspection terminal for inspecting the voltage of the constant voltage node.

  The electronic component circuit with an input circuit according to the present invention includes an inspection terminal for inspecting the voltage of the constant voltage node. With this inspection terminal, it can be easily inspected whether or not the voltage of the constant voltage node is a predetermined constant voltage Vc. In addition, in the process of manufacturing the electronic component circuit with an input circuit according to the present invention, or in the final inspection stage, it is possible to easily inspect whether the members constituting the constant voltage circuit such as the constant voltage source are correctly mounted and connected. it can.

In the above-described conventional circuit, that is, a circuit including a diode and a voltage dividing circuit in each input circuit, the members (two resistance elements) constituting the voltage dividing circuit are correctly connected (having the correct resistance value). In order to be able to confirm whether or not a resistance element is connected, it is necessary to provide a test pad for each input circuit. That is, it is necessary to provide as many test pads as the number of input circuits and test each of them.
In comparison with this, in the electronic component circuit with an input circuit according to the present invention, it is not necessary to provide a large number of inspection pads and inspect them, and the voltage of one constant voltage node (constant voltage circuit) is inspected at the inspection terminal. There are also benefits.

  Furthermore, in the electronic component circuit with an input circuit according to any one of the above, at least one of the plurality of input circuits is closer to the circuit input end than the anode of the diode connected to the input voltage limiting circuit Therefore, an electronic component circuit with an input circuit, which is connected to a pull-up power supply line having a pull-up voltage higher than the maximum input voltage Vmax through a resistor, is preferable.

There is a case where a circuit configuration in which an input circuit is connected via a resistor to a pull-up power supply circuit having a pull-up voltage higher than the maximum input voltage Vmax, such as a battery power supply in an in-vehicle electronic component circuit, is sometimes used. In this case, a voltage exceeding the maximum input voltage Vmax may be applied to the component input terminal to which the input circuit is connected.
However, by providing an input voltage limiting circuit as in the electronic component circuit with an input circuit of the present invention, the voltage input to the component input terminal even when the input circuit is connected to the pull-up power supply circuit as described above. Can be reliably controlled to be equal to or lower than the maximum input voltage Vmax to protect the electronic component.

  Furthermore, in the electronic component circuit with an input circuit according to any one of the above-described items, at least one of the electronic components is a microcomputer driven by a drive voltage Vd equal to the maximum input voltage Vmax, The voltage circuit may be an electronic component circuit with an input circuit formed by generating the constant voltage Vc using the drive voltage Vd.

In the microcomputer driven by the drive voltage Vd, the maximum input voltage Vmax of the component input terminal is often equal to the drive voltage Vd.
In the electronic component circuit with an input circuit according to the present invention, the constant voltage circuit uses the drive voltage Vd of the microcomputer and generates the constant voltage Vc from the drive voltage Vd. Therefore, in the electronic component circuit with an input circuit according to the present invention, when operating the microcomputer and the input voltage limiting circuit, a constant voltage source for generating the constant voltage Vc is prepared separately from the drive power supply for supplying the drive voltage Vd. In addition, it is not necessary to route wiring from a separate constant voltage circuit, and this circuit can be driven more easily.

  Examples of the constant voltage circuit that generates the constant voltage Vc using the drive voltage Vd include a voltage dividing circuit that divides the drive voltage Vd by resistance and a circuit that divides the drive voltage Vd by a resistor and a Zener diode. Further, there is a constant voltage circuit that divides the drive voltage Vd by a resistor and a Zener diode, inputs the divided voltage to the base terminal of the NPN transistor, and connects the collector to the drive voltage Vd to obtain a constant voltage emitter output. Can be mentioned.

(Reference form)
First, an electronic component circuit with an input circuit according to a reference embodiment will be described (see FIG. 5).
The electronic circuit (electronic component circuit with an input circuit) EC is composed of a microcomputer EP, a diode D1, resistors R2 to R5, a capacitor C1, and circuit wiring for connecting them, which are arranged on a circuit board BD. .
The microcomputer EP has a plurality of input terminals INA, INB, INC... For example, all of the input circuits IPA, IPB, IPC connected to the input terminals INA, INB, INC are shown in FIG. It has a circuit configuration.

Among these, the input circuit IPA transmits an input signal input to the circuit input terminal ITA to the input terminal INA. The input circuit IPA is connected to a pull-up resistor R2 connected to the battery voltage VB. Further, on the input terminal INA side, a low-pass filter type noise filter FL composed of a resistor R3 and a capacitor C1 is interposed.
The input circuit IPC has the same circuit configuration. The input circuit IPB is the same as the input circuits IPA and IPC except that the pull-up resistor R2 connected to the battery voltage VB is not connected.

  By the way, the microcomputer EP is driven at a constant drive voltage Vd (for example, 5 V). Therefore, the maximum allowable input voltage Vmax at the input terminals INA, INB, INC... Of the microcomputer EP is equal to the drive voltage Vd (for example, 5V).

Therefore, in the electronic circuit EC of the present embodiment, for example, in the input circuit IPA, in order to prevent the input voltage Vi1 input to the input terminal INA from exceeding the maximum input voltage Vmax (= Vd), The input circuit IPA is connected to the drive voltage Vd via the diode D1 on the input terminal INA side of the resistor R3. Specifically, the anode D1a of the diode D1 is connected to the input circuit IPA, and the cathode D1c is connected to the drive voltage Vd.
As a result, even when a large voltage is applied to the circuit input terminal IT1, the portion of the anode D1a of the diode D1 in the input circuit IP is at most higher than the drive voltage Vd by the forward voltage drop Vf of the diode D1. Limited to voltage value.
However, with this alone, the input voltage Vi1 may exceed the maximum input voltage Vmax (= Vd). Therefore, the input voltage Vi input to the input terminal INA is further reduced by appropriately reducing the magnitude of the input signal by using a resistance voltage dividing circuit DV composed of the resistors R4 and R5. Does not exceed the maximum input voltage Vmax (= Vd).
The same applies to the input circuits IPB and IPC.

  However, in the circuit configuration of this reference embodiment, in addition to the diode D1, a resistor divider circuit DV (resistors R4 and R5) is required for each input terminal INA and the like in order to limit the input voltage. For this reason, the number of parts increases and the circuit becomes complicated.

Further, in the circuit configuration such as the input circuit IPA shown in the reference embodiment, the step signal is input using the switch SW1 and the resistor R1, and the voltage appearing at the circuit input terminal IT1 is monitored to thereby detect the resistors R2, R3. Further, it is possible to determine whether a component having the correct characteristics is used and correctly connected as the capacitor C1.
However, regarding the resistors R4 and R5 constituting the resistor voltage dividing circuit DV, it is impossible to determine whether or not components having the correct characteristics are used and correctly connected by monitoring the voltage appearing at the circuit input terminal IT1. .
Therefore, a test pad CHP is provided between the resistor R4 and the resistor R5, and the voltage at the test pad CHP is detected together to determine whether the resistors R4 and R5 are appropriate. In this case, it is necessary to provide the inspection pad CHP, and the inspection becomes complicated.

(Embodiment)
Therefore, in the present invention, the following is performed. First, after explaining the principle of the present invention (see FIG. 1), the present embodiment will be described (see FIG. 2).
An electronic circuit (electronic component circuit with an input circuit) 10 includes a microcomputer 2, a constant voltage circuit 3 and diodes 6A, 6B, and 6C constituting an input voltage limiting circuit 9 disposed on the circuit board 1, and an input. The circuit 4A, 4B, 4C and the like are constituted by circuit wiring for connecting these components.
The microcomputer 2 has a plurality of input terminals INA, INB, INC,... Of which, for example, the input terminals INA, INB, INC are connected to the input circuits 4A, 4B, 4C, respectively. Note that the maximum input voltage of the input terminals INA, INB, INC, etc. is Vmax.

Of the input voltage limiting circuit 9, the constant voltage circuit 3 generates a predetermined node voltage Vc. For this reason, the constant voltage node 5 connected thereto is set to this node voltage Vc. Further, in the input voltage limiting circuit 9, the diodes 6 </ b> A, 6 </ b> B, 6 </ b> C are respectively interposed between the input circuits 4 </ b> A, 4 </ b> B, 4 </ b> C and the constant voltage node 5. Specifically, the anodes 6Aa, 6Ba, and 6Ca of the diodes 6A, 6B, and 6C are connected to the input circuits 4A, 4B, and 4C, and the cathodes 6Ac, 6Bc, and 6Cc are connected to the constant voltage node 5, respectively.
As a result, even if a large voltage is applied to the circuit input terminals IT1, IT2, IT3, the input voltages Vi1, Vi2, Vi3 of the input terminals INA, INB, INC are at a maximum such as the diode 6A than the constant voltage node Vc. It is limited to a voltage value higher by the forward voltage drop Vf.

Therefore, considering the maximum input voltage Vmax of the input terminals INA, INB, INC, etc., the node voltage Vc generated by the constant voltage circuit 3 is set to Vc <Vmax−Vf. With this setting, the input voltages Vi1, Vi2, Vi3 input to the input terminals INA, INB, INC can be prevented from exceeding the maximum input voltage Vmax (Vi1, Vi2, Vi3 <Vmax).
As can be easily understood when compared with the above-described reference form (see FIG. 5), the resistance dividing circuit DV as shown in the reference form is provided for each of the input circuits 4A, 4B, and 4C. Therefore, the circuit configuration of the input circuit 4A and the like can be simplified.

Next, an embodiment will be described with reference to FIG.
In the present embodiment shown in FIG. 2, the input circuit 4A related to the input terminal INA among the plurality of input terminals INA, INB, INC and the like will be mainly described, but the same applies to the input circuit 4C. The input circuit 4B is the same as the input circuits 4A and 4C except that the pull-up resistor 72 connected to the battery voltage VB is not connected.

  An electronic circuit (electronic component circuit with an input circuit) 10 includes a microcomputer 2, a constant voltage circuit 3 and diodes 6A, 6B, and 6C that constitute an input voltage limiting circuit 9 and a pull-up power supply circuit. 7, 7, 7, noise filters 8, 8, 8, and input circuits 4 </ b> A, 4 </ b> B, 4 </ b> C and constant voltage node 5, etc.

  Among these, the microcomputer 2 has a plurality of input terminals INA, INB, INC,... Of which, for example, the input terminal INA is connected to the input circuit 4A. The microcomputer 2 is driven with a drive voltage Vd (for example, 5 V). Therefore, the maximum input voltage Vmax allowed at the input terminals INA, INB, INC... Of the microcomputer 2 is equal to the drive voltage Vd (for example, 5V).

  Of the input voltage limiting circuit 9, the constant voltage circuit 3 generates a predetermined node voltage Vc. Specifically, the constant voltage circuit 3 includes a regulated power supply 31 that generates a constant drive voltage Vd, and two resistors (a first divided resistor 32 and a second resistor) that are connected in series to the drive voltage Vd. The resistance is divided by the dividing resistor 33) to generate a constant node voltage Vc. For this reason, the constant voltage node 5 connected thereto is set to this node voltage Vc. The constant voltage node 5 is connected to a test terminal CH described later.

On the other hand, the input circuit 4A is a circuit that transmits an input signal input to the circuit input terminal ITA to the input terminal INA. In this input circuit 4A, a pull-up power supply circuit 7 and a noise filter 8 are formed. The pull-up power circuit 7 includes a battery power line 71 having a battery voltage VB of a battery (not shown) and a pull-up resistor 72 connected to one end of the battery power line 71. The other end of the pull-up resistor 72 is connected to the battery power line 71. It is connected to the input circuit 4A. The battery voltage VB is about 14V, for example, and is larger than the drive voltage Vd (for example, 5V), and therefore the maximum input voltage Vmax of the input terminal INA of the microcomputer 2.
Further, a low-pass filter type noise filter 8 including a resistor 81 and a capacitor 82 is interposed on the input terminal INA side from the battery power line 71. Among these, the resistor 81 is disposed in series between the circuit input terminal ITA and the input terminal INA. On the other hand, the capacitor 82 is disposed between the input terminal INA and the ground GND.

Further, a diode 6 A constituting the input voltage limiting circuit 9 is interposed between the input circuit 4 A (input terminal INA) and the constant voltage node 5. Specifically, the anode 6Aa of the diode 6A is connected to the input circuit 4A (input terminal INA), and the cathode 6Ac is connected to the constant voltage node 5.
As a result, even if a large voltage is applied to the circuit input terminal IT1 or the pull-up power supply circuit 7 is connected, the input voltage Vi1 input from the input circuit 4A to the input terminal INA is constant even at the maximum. The voltage value is limited to a voltage value higher than the voltage node Vc by the forward voltage drop Vf of the diode 6A.

  Further, in the present embodiment, the node voltage Vc generated by the constant voltage circuit 3 is set to Vc <Vmax−Vf (= Vd−Vf) in consideration of the maximum input voltage Vmax of the input terminal INA. As a result, even if a large voltage is applied to the circuit input terminal IT1 or the pull-up power supply circuit 7 is connected, the input voltage Vi1 to the input terminal INA is at most the maximum input voltage Vmax (= Vd ) (Vi1 <Vmax). Accordingly, it is possible to prevent problems such as failure of the microcomputer 2 by applying an excessive voltage to the input terminal INA.

1, the cathodes 6Bc and 6Cc of the input terminals INB and INC are connected to the constant voltage node 5 using the diodes 6B and 6C in the same manner as the principle of the present invention is described. The anodes 6Ba and 6Ca are connected to the input circuits 4B and 4C (input terminals INB and INC). By doing so, the input voltages Vi2 and Vi3 input to the input terminals INB and INC can be made smaller than the maximum input voltage Vmax (= Vd) at the maximum.
In addition, unlike the above-described reference mode (see FIG. 5), it is not necessary to provide the resistance dividing circuit DV for each of the input circuits 4A, 4B, and 4C, so that the circuit configuration of the input circuit 4A and the like can be simplified.

Note that the input circuit (for example, the input circuit 4A) of the present embodiment (see FIG. 1) is checked as follows to check whether correct parts are correctly connected to each part and to operate correctly. Can be inspected.
First, the test resistor R1 connected to the ground GND is connected to the circuit input terminal IT1 of the input circuit 4A through the switch SW1. The switch SW1 is turned on while monitoring the voltage at the circuit input terminal IT1, and a step-like input signal is input to the circuit input terminal IT1. In this case, it is possible to determine whether or not correct components are correctly connected and operating correctly for the resistors 72 and 81, the capacitor 82, and the diode 6A from the time change of the voltage at the circuit input terminal IT1. .

However, the resistances 32 and 33 of the constant voltage circuit 3 cannot be determined by the above inspection.
Therefore, in the present embodiment, as described above, the inspection terminal CH connected to the constant voltage node 5 is provided. At the inspection terminal CH, it can be easily checked whether or not the voltage of the constant voltage node 5 is a predetermined constant voltage Vc. In addition, the resistors 32 and 33 can be inspected whether correct components are correctly mounted and connected, and whether or not they are operating correctly.
Unlike the case of the reference embodiment described above, it is sufficient to provide one inspection terminal CH for the constant voltage circuit 3.

(Modification 1)
Next, a first modification of the above-described embodiment will be described with reference to FIG. In addition, the same number is attached | subjected about the part of the same content as embodiment, and description is abbreviate | omitted or simplified.

As can be easily understood when compared with FIG. 2, in the embodiment, the regulated power supply 31 is provided in the constant voltage circuit 3 in the input voltage limiting circuit 9, and the constant voltage Vc is obtained by using this.
On the other hand, in the first modification, an external constant voltage source CV that generates an external constant voltage Ve is provided outside the electronic circuit 110 (circuit board 101), and the input voltage limiting circuit 190 includes the constant voltage circuit 130. The constant voltage Vc is obtained using the external constant voltage Ve. Specifically, the external constant voltage Ve is input to the regulated power supply line 131 through the constant voltage terminal VIN, and the external constant voltage Ve is appropriately increased by the first divided resistor 132 and the second divided resistor 133. To obtain a constant voltage Vc.
Note that the microcomputer 2 is separately driven by the drive voltage Vd.

Also in the first modification, the node voltage Vc generated by the constant voltage circuit 130 is set to Vc <Vmax−Vf (= Vmax−Vd) in consideration of the magnitude of the external constant voltage Ve. By setting in this way, even if a large voltage is applied to the circuit input terminal IT1, the input voltage Vi1 of the input terminal INA can be made smaller than the maximum input voltage Vmax (= Vd) at the maximum. Accordingly, it is possible to prevent problems such as failure of the microcomputer 2 by applying an excessive voltage to the input terminal INA.
In addition, the same operation and effect can be obtained by the same configuration as the embodiment.

(Modification 2)
Next, with reference to FIG. 4A, the second modification of the first embodiment will be described.
In the above-described embodiment (see FIG. 1), in the constant voltage circuit 3, the constant voltage Vc is obtained by resistance division between the first divided resistor 32 and the second divided resistor 33. The same applies to the constant voltage circuit 130 of the first modification.

  On the other hand, in the second modification, a constant voltage circuit 230 shown in FIG. 4A is used in place of the constant voltage circuits 3 and 130. The constant voltage circuit 230 obtains the constant voltage Vc from the regulated power supply line 231 that is set to the drive voltage Vd (or the external constant voltage Ve) using the Zener diode 233. Specifically, a resistor 232 having one end connected to the regulated power supply line 231 and a Zener diode 233 having an anode connected to the ground are connected in series, and the potential of the cathode 233c is set to a constant voltage Vc.

  In this way, the constant voltage node 5 can be set to the constant voltage Vc. In addition, since the Zener diode 233 is used, there is an advantage that the stability of the constant voltage Vc can be increased.

(Modification 3)
Next, with reference to FIG. 4B, a third modification of the first embodiment will be described.
In the third modification, a constant voltage circuit 330 shown in FIG. 4B is used in place of the constant voltage circuits 3 and 130. The constant voltage circuit 330 obtains the constant voltage Vc from the regulated power supply line 331 that is set to the drive voltage Vd (or the external constant voltage Ve) using the Zener diode 333 and the transistor 334. Specifically, a resistor 332 having one end connected to the regulated power supply line 331 and a Zener diode 333 having an anode connected to the ground are connected in series. Further, the base B of the NPN transistor 334 is connected to the cathode 333 c and the collector C is connected to the regulated power supply line 331. Thereby, the constant voltage Vc can be obtained from the emitter E of the NPN transistor 334.

  In this way, the constant voltage node 5 can be set to the constant voltage Vc. Moreover, since the transistor 334 is used in addition to the Zener diode 233, there is an advantage that the magnitude of the constant voltage Vc can be stably maintained even when a large current flows through each diode 6A or the like.

In the above, the present invention has been described with reference to the embodiment and the first to third modifications. However, the present invention is not limited to the embodiment and the like, and is appropriately modified and applied without departing from the gist thereof. Needless to say, it can be done.
For example, in the embodiment and the like, an electronic component having an input terminal is shown in which one microcomputer 2 is mounted on the circuit board 1 or the like. However, the present invention can also be applied to a plurality of electronic components having input terminals such as a plurality of microcomputers.

It is a circuit diagram explaining the principle of this invention. It is a circuit diagram which shows the electronic component circuit with an input circuit which concerns on embodiment. It is a circuit diagram which shows the electronic component circuit with an input circuit which concerns on the modification 1. FIG. FIG. 10 is a circuit diagram illustrating another example of a constant voltage circuit according to modification examples 2 and 3. It is a circuit diagram which shows the electronic component circuit with an input circuit which concerns on a reference form.

Explanation of symbols

1,101 Circuit board IT1, IT2, IT3 Circuit input terminal CH Inspection terminal 2 Microcomputer (electronic component)
INA, INB, INC (microcomputer) input terminals (component input terminals)
3, 130, 230, 330 Constant voltage circuit 31 Adjusted power supply 131, 231, 331 Adjusted power supply line 32, 132 First divided resistor 33, 133 Second divided resistor 232, 332 Resistor 233, 333 Zener diode 233c, 333c ( Cathode 334 of Zener diodes 4P, 4B, 4C Input circuits Vi1, Vi2, Vi3 (input to input terminal) Input voltage 5 Constant voltage nodes 6A, 6B, 6C Diodes 6Aa, 6Ba, 6Ca (diode) anode 6Ac, 6Bc, 6Cc (diode) cathode Vf (diode) forward voltage drop 7 pull-up power supply circuit 71 battery power supply line (pull-up power supply line)
72 Pull-up resistor VB Battery voltage (pull-up voltage)
8 Noise Filter 81 Resistor 82 Capacitor 9,190 Input Voltage Limiting Circuit 10, 110 Electronic Circuit (Electronic Component Circuit with Input Circuit)
Vc node voltage (constant voltage)
Vd Drive voltage CV External constant voltage source Ve External constant voltage GND Ground

Claims (4)

One or more electronic components having a plurality of component input terminals;
A plurality of input circuits each having a circuit input terminal, connected to each of the component input terminals, and inputting a signal input to the circuit input terminal to the component input terminal as an input signal;
An input voltage limiting circuit that regulates an input voltage Vi of the input signal input to each of the component input terminals to be equal to or lower than a maximum input voltage Vmax that can be input to the component input terminal,
A constant voltage circuit having a constant voltage node as a predetermined constant voltage Vc;
A plurality of diodes interposed between the constant voltage node and the plurality of input circuits, each having an anode connected to the input circuit and a cathode connected to the constant voltage node;
When the forward voltage drop of the diode is Vf,
The constant voltage Vc at the constant voltage node is made smaller than a value obtained by subtracting the forward voltage drop Vf from the maximum allowable voltage Vmax (Vc <Vmax−Vf).
An electronic component circuit with an input circuit comprising an input voltage limiting circuit. An electronic component circuit with an input circuit according to claim 1,
An electronic component circuit with an input circuit, comprising an inspection terminal for inspecting the voltage of the constant voltage node. An electronic component circuit with an input circuit according to claim 1 or 2,
At least one of the plurality of input circuits is
An input circuit connected via a resistor to a pull-up power supply line having a pull-up voltage higher than the maximum input voltage Vmax on the circuit input end side of the anode of the diode connected to the input voltage limiting circuit. With electronic component circuit. An electronic component circuit with an input circuit according to any one of claims 1 to 3,
At least one of the electronic components is a microcomputer driven with a drive voltage Vd equal to the maximum input voltage Vmax,
The constant voltage circuit is an electronic component circuit with an input circuit formed by generating the constant voltage Vc using the drive voltage Vd.

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