JP2016200506A - Circuit arrangement and ground opening detection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit arrangement and a ground opening detection system that can easily detect ground opening.SOLUTION: A circuit arrangement 1 includes a ground terminal 111, an internal voltage generation circuit 3, a voltage input terminal 131, and a detection circuit 4. The ground terminal 111 can be electrically connected to the external ground 21, the internal voltage generation circuit 3 generates a first voltage V1 based on the potential of the ground terminal 111, and the voltage input terminal 131 can receive a second voltage V2 based on the potential of the external ground 21. The detection circuit 4 detects ground opening with no electrical connection between the ground terminal 111 and the external ground 21, on the basis of the first and second voltages V1 and V2.SELECTED DRAWING: Figure 1

Description

  The present invention generally relates to a circuit device, a ground open detection system, and more particularly to a circuit device capable of detecting a ground open in which a ground terminal is not electrically connected to an external ground, and a ground open detection system using the same. .

  Conventionally, a circuit device (integrated circuit device) capable of detecting a ground open in which a ground terminal is not electrically connected to an external ground has been provided (see, for example, Patent Document 1). The configuration described in Patent Document 1 detects a ground open by comparing the potential of the ground terminal with a normal ground level.

JP 2010-183168 A

  However, in Patent Document 1, since the ground potential is used as a comparison parameter, the degree of freedom in designing the threshold is low, and it may be difficult to detect open ground terminals.

  The present invention has been made in view of the above reasons, and an object thereof is to provide a circuit device and a ground open detection system capable of easily detecting a ground open.

  The circuit device of the present invention includes a ground terminal configured to be electrically connectable to an external ground, an internal voltage generation circuit that generates a first voltage based on the potential of the ground terminal, and a potential of the external ground. A ground input in which the ground terminal and the external ground are not electrically connected based on the voltage input terminal configured to be able to input a second voltage as a reference, and the first voltage and the second voltage. And a detection circuit for detecting.

  In this circuit device, the detection circuit converts the first voltage and the second voltage into digital values and outputs the difference, and the difference between the first voltage and the second voltage output from the conversion circuit And an arithmetic circuit for detecting the ground open based on the above.

  In this circuit device, the detection circuit includes a comparator that compares the first voltage with the second voltage and detects the ground open based on a magnitude relationship between the first voltage and the second voltage. It is preferable.

  Preferably, the circuit device further includes a functional terminal configured to be electrically connectable to the external ground, and an impedance element electrically connected between the ground terminal and the functional terminal.

  In this circuit device, it is preferable to further include a switch element that switches between electrical conduction and interruption between both ends of the impedance element.

  A ground open detection system according to the present invention includes the circuit device and the external ground electrically connected to the functional terminal.

  The ground open detection system further includes an external voltage generation circuit that has a plurality of resistors, generates the second voltage by resistance voltage division, and inputs the second voltage to the voltage input terminal.

  In the present invention, since the first voltage based on the potential of the ground terminal is compared with the second voltage based on the external ground, the voltage comparison is facilitated, and the ground open can be easily detected. is there.

It is a circuit block diagram which shows the circuit apparatus and ground open detection system in embodiment. 2A, 2B, and 2C are circuit configuration diagrams showing modifications of the output circuit in the embodiment. It is a circuit block diagram which shows the modification of the functional circuit in embodiment. It is a circuit block diagram which shows the modification of the ESD protection element in embodiment. It is a circuit block diagram which shows the modification of the ground open detection system in embodiment. It is a circuit block diagram which shows the modification of the detection circuit in embodiment. It is a circuit block diagram which shows the modification of the circuit device in embodiment. It is a circuit block diagram which shows the modification of the circuit device in embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment)
FIG. 1 shows a schematic configuration diagram of a circuit device 1 and a ground open detection system 100 according to the present embodiment. The circuit device 1 includes a microcomputer in which an integrated circuit 10 (IC (Integrated Circuit), LSI (Large Scale Integration)) formed in a chip shape is enclosed in a package. The terminals of the integrated circuit 10 are electrically connected to the lead frame exposed from the package by wire bonding. The circuit device 1 is mounted on the circuit board 2 by soldering the lead frame to the conductor pattern of the circuit board 2, and the integrated circuit 10 and the conductor pattern of the circuit board 2 are electrically connected. The circuit device 1 is not limited to a microcomputer, and may have other configurations.

  The circuit device 1 and the ground open detection system 100 according to the present embodiment have a ground open detection function. The term “ground open” as used herein refers to a state in which the ground terminal 111 of the integrated circuit 10 is not electrically connected to a circuit ground (hereinafter referred to as an external ground 21) formed on the circuit board 2. More specifically, the ground terminal 111 and the external ground 21 are electrically connected to each other by cutting wire bonding that connects the ground terminal 111 and the lead frame or by poor soldering between the lead frame and the conductor pattern of the circuit board 2. Indicates not connected.

  Below, the circuit apparatus 1 of this embodiment and the ground open detection system 100 using the circuit apparatus 1 are demonstrated.

  The integrated circuit 10 of this embodiment includes a ground terminal 111 and a power supply terminal 121 as terminals that are electrically connected to the conductor pattern of the circuit board 2.

  The ground terminal 111 is electrically connected to the ground wiring 112 of the integrated circuit 10, and the ground terminal 111 and the ground wiring 112 function as a circuit ground of the integrated circuit 10 (hereinafter referred to as an internal ground 11). The ground terminal 111 is electrically connected to an external ground 21 that is a circuit ground of the circuit board 2. When the ground terminal 111 is electrically connected to the external ground 21, the internal ground 11 and the external ground 21 have the same potential.

  The power supply terminal 121 is electrically connected to the power supply wiring 122 of the integrated circuit 10. Here, the circuit board 2 is provided with a power supply 22 (for example, a regulator element or the like), and the power supply 22 generates a predetermined power supply voltage based on the potential of the external ground 21. The power supply terminal 121 is electrically connected to the positive electrode of the power supply 22. In other words, the circuit device 1 is driven by applying a power supply voltage from the power supply 22.

  The integrated circuit 10 includes an internal voltage generation circuit 3, a detection circuit 4, and a functional circuit 5.

  The internal voltage generation circuit 3 is electrically connected to the ground wiring 112, and generates a predetermined first voltage V 1 based on the potential of the internal ground 11 using the power supply voltage supplied from the power supply 22. Then, the internal voltage generation circuit 3 outputs the generated first voltage V1 to the detection circuit 4.

  The detection circuit 4 includes a conversion circuit 41 and an arithmetic circuit 42.

  The conversion circuit 41 includes an A / D converter, converts the first voltage V1 generated by the internal voltage generation circuit 3 into a digital value, and outputs the digital value to the arithmetic circuit 42. Furthermore, the conversion circuit 41 converts the second voltage V2 generated by the external voltage generation circuit 23 provided on the circuit board 2 into a digital value. The external voltage generation circuit 23 includes a resistor R1 and a resistor R2 connected in series between the output terminals of the power supply 22. Then, the external voltage generation circuit 23 generates a predetermined second voltage V2 based on the potential of the external ground 21 by resistance-dividing the power supply voltage output from the power supply 22. A connection midpoint between the resistor R1 and the resistor R2 is electrically connected to the voltage input terminal 131 of the integrated circuit 10. The second voltage V <b> 2 generated by the external voltage generation circuit 23 is input to the conversion circuit 41 via the voltage input terminal 131. The conversion circuit 41 converts the second voltage V2 generated by the external voltage generation circuit 23 into a digital value and outputs the digital value to the arithmetic circuit 42. That is, the conversion circuit 41 converts the first voltage V1 based on the potential of the internal ground 11 and the second voltage V2 based on the potential of the external ground 21 into digital values and outputs them to the arithmetic circuit 42.

  The arithmetic circuit 42 compares the first voltage V1 and the second voltage V2, and generates a detection signal based on the difference between the first voltage V1 and the second voltage V2. For example, when the difference between the first voltage V1 and the second voltage V2 is within a predetermined threshold range, the arithmetic circuit 42 sets the signal level of the detection signal to a low level. In addition, when the difference between the first voltage V1 and the second voltage V2 is outside the threshold range, the arithmetic circuit 42 sets the signal level of the detection signal to a high (Hi) level. Then, the arithmetic circuit 42 outputs the generated detection signal to the first control circuit 24 provided on the circuit board 2 via the signal output terminal 141 of the integrated circuit 10.

  The functional circuit 5 includes an output circuit 51 and an ESD protection element 52 (ESD: Electro Static Discharge).

  The output circuit 51 includes a switch element Q1 made of an n-channel depletion type MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The drain of the switch element Q1 is electrically connected to the external ground 21 via the function terminal 151 of the integrated circuit 10. In addition, the source and back gate of the switch element Q1 are electrically connected to the ground wiring 112. The switch element Q <b> 1 has a gate connected to the second control circuit 25 via the signal input terminal 161 of the integrated circuit 10. The second control circuit 25 controls the switch element Q1 by outputting a control signal to the switch element Q1 via the signal input terminal 161. In the present embodiment, the second control circuit 25 maintains the switch element Q1 in the OFF state by setting the control signal to a low level. That is, the function terminal 151 is an output terminal of the function circuit 5 (output circuit 51), and the output circuit 51 switches between the ON state and the OFF state of the switch element Q1, thereby providing a low level output and a high impedance (HiZ) output. It is configured to be switchable. Then, the switching element Q1 is maintained in the OFF state by the second control circuit 25, so that the output circuit 51 maintains a high impedance output. A processing circuit that receives a control signal from the second control circuit 25 and turns on or off the switch element Q1 may be provided between the switch element Q1 and the second control circuit 25.

  The ESD protection element 52 includes a diode D1. The diode D1 has an anode electrically connected to the ground wiring 112 and a cathode electrically connected to the functional terminal 151, and allows a current to flow only in the direction from the ground wiring 112 to the functional terminal 151. That is, the diode D1 functions as an impedance element electrically connected between the ground terminal 111 and the functional terminal 151, and a threshold voltage (forward voltage) is generated between both ends of the diode D1 when a current flows through the diode D1. Occurs. Since the switch element Q1 is connected in parallel with the diode D1, the switch element Q1 is turned on to electrically connect both ends of the diode D1, and the switch element Q1 is turned off to turn both ends of the diode D1 on. The gap is electrically disconnected.

  In addition, the ground open detection system 100 according to the present embodiment includes the circuit device 1 described above, the external ground 21 electrically connected to the function terminal 151, and the external voltage generation for inputting the second voltage V2 to the voltage input terminal 131. The circuit 23 is provided.

  Next, the ground open detection function in which the ground terminal 111 is not electrically connected to the external ground 21 will be described. First, the normal operation when the ground terminal 111 and the external ground 21 are electrically connected (not ground open) will be described.

  When the ground terminal 111 and the external ground 21 are electrically connected, the potential of the internal ground 11 (the ground terminal 111 and the ground wiring 112) and the potential of the external ground 21 are the same potential. Therefore, the first voltage V1 and the second voltage V2 are voltages based on the potential of the external ground 21 (= potential of the internal ground 11). Here, in the present embodiment, the resistance ratio of the resistors R1 and R2 and the voltage of the first voltage V1 in the normal state so that the difference between the first voltage V1 and the second voltage V2 in the normal state is within the threshold range. Value is set. Therefore, when the ground open is not occurring normally, the signal level of the detection signal output from the arithmetic circuit 42 to the first control circuit 24 is low. When the signal level of the detection signal is low, the first control circuit 24 recognizes that the circuit device 1 is in a normal state where no ground open has occurred.

  Next, the operation when the ground terminal 111 is not electrically connected to the external ground 21 when the ground is opened will be described.

  As described above, the output circuit 51 of the functional circuit 5 maintains the high impedance output by turning off the switch element Q1, that is, the switch element Q1 electrically cuts off both ends of the diode D1. Therefore, when the ground terminal 111 and the external ground 21 are not electrically connected, the ESD protection element 52 (diode D1) is turned on, and the external ground 21 is connected from the ground wiring 112 via the ESD protection element 52 and the function terminal 151. A current flows toward. In FIG. 1, a schematic path of current when the ground is open is indicated by an arrow Y1. When a current flows through the ESD protection element 52 (diode D1), a potential difference is generated between the external ground 21 and the internal ground 11 (ground wiring 112). That is, when a ground open occurs, the potential of the internal ground 11 becomes higher than the potential of the external ground 21 by the threshold voltage of the ESD protection element 52 (diode D1). As the potential of the internal ground 11 becomes higher than the potential of the external ground 21, the first voltage V1 based on the potential of the internal ground 11 also increases. Here, the first voltage V1 based on the potential of the external ground 21 (= internal ground 11) in the normal state is V1a, the first voltage V1 based on the potential of the external ground 21 when the ground is open is V1b, and ESD protection. The threshold voltage of the element 52 is Vth. In this case, the first voltage V1b when the ground is open is expressed by the following formula (1).

V1b = V1a + Vth (1)
On the other hand, since the second voltage V2 is a voltage based on the potential of the external ground 21, the voltage does not change even when a ground open occurs. That is, a difference occurs between the first voltage V1 based on the potential of the internal ground 11 and the second voltage V2 based on the potential of the external ground 21 between the normal time and the ground open state. In the present embodiment, the resistance ratio of the resistors R1 and R2 and the voltage value of the first voltage V1 in the normal state are such that the difference between the first voltage V1 and the second voltage V2 when the ground is open is outside the threshold range. Is set. Therefore, when the ground is opened, the signal level of the detection signal output from the arithmetic circuit 42 to the first control circuit 24 is high. When the signal level of the detection signal is high, the first control circuit 24 recognizes that a ground open has occurred in the circuit device 1. When the first control circuit 24 recognizes that the circuit device 1 is in a state where a ground open has occurred, for example, the first control circuit 24 stops the operation of the circuit device 1.

  As described above, the circuit device 1 according to this embodiment includes the ground terminal 111, the internal voltage generation circuit 3, the voltage input terminal 131, and the detection circuit 4. The ground terminal 111 is configured to be electrically connected to the external ground 21. The internal voltage generation circuit 3 generates a first voltage V1 based on the potential of the ground terminal 111. The voltage input terminal 131 is configured to be able to input a second voltage V2 with reference to the potential of the external ground 21. The detection circuit 4 detects a ground open in which the ground terminal 111 and the external ground 21 are not electrically connected based on the first voltage V1 and the second voltage V2.

  With the configuration described above, the circuit device 1 according to the present embodiment has the first voltage V1 based on the potential of the internal ground 11 (the ground terminal 111 and the ground wiring 112) and the second voltage V2 based on the potential of the external ground 21. Based on the above, the ground open is detected. That is, the first voltage V1 higher than the internal ground 11 by a predetermined voltage is compared with the second voltage V2 higher than the external ground 21 by a predetermined voltage to determine whether a ground open has occurred. Therefore, the degree of freedom in designing the values of the first voltage V1 and the second voltage V2, and the threshold value (threshold range) used for determining whether or not the ground open has occurred is increased, and the ground open can be easily detected.

  The circuit device 1 of the present embodiment is a functional terminal 151 configured to be electrically connectable to the external ground 21 and an impedance element electrically connected between the ground terminal 111 and the functional terminal 151. And a diode D1 (ESD protection element 52). Further, the ground open detection system 100 includes a circuit device 1 and an external ground 21 that is electrically connected to the function terminal 151.

  When the current path flowing from the integrated circuit 10 to the external ground 21 is interrupted by the ground opening, and the potential of the internal ground 11 rises to near the power supply voltage, the integrated circuit 10 itself may become inoperable. In the present embodiment, due to the configuration described above, the rise in the potential of the internal ground 11 when a ground open occurs is only the threshold voltage of the ESD protection element 52. Therefore, it is possible to prevent the integrated circuit 10 from becoming inoperable.

  The detection circuit 4 includes a conversion circuit 41 and an arithmetic circuit 42. The conversion circuit 41 converts the first voltage V1 and the second voltage V2 into digital values and outputs them. The arithmetic circuit 42 detects a ground open based on the difference between the first voltage V1 and the second voltage V2 output from the conversion circuit 41.

  With the above configuration, the detection circuit 4 determines whether or not a ground open has occurred depending on whether or not the difference between the first voltage V1 and the second voltage V2 is within a threshold range. Therefore, since a margin can be set in the threshold range, erroneous detection of ground open due to noise or the like can be prevented.

  Here, in general, the microcomputer often includes a voltage generation circuit that generates a predetermined voltage based on the potential of the internal ground 11, and an A / D converter that converts an input value into a digital value. This voltage generation circuit can function as the internal voltage generation circuit 3, and the A / D converter can function as the conversion circuit 41. Therefore, the circuit device 1 according to the present embodiment can be configured using a general-purpose microcomputer, and the ground open detection function can be realized, so that the cost can be reduced. Furthermore, since a circuit dedicated to ground open detection is unnecessary, the integrated circuit 10 can be downsized.

  Furthermore, the output circuit 51 of the functional circuit 5 in the present embodiment is configured to be able to switch between a high impedance output and a low level output. When the signal level of the control signal output from the second control circuit 25 to the functional circuit 5 is set to a high level, the switch element Q1 is turned on and the output circuit 51 becomes a low level output. When the switch element Q1 is turned on, both ends of the diode D1 (ESD protection element 52) are electrically connected, that is, the internal ground 11 (ground terminal 111, ground wiring 112) and the function terminal 151 are short-circuited. . Thus, when a ground open occurs, a current flows from the ground wiring 112 to the external ground 21 via the switch element Q1 and the function terminal 151. Since the switch element Q1 is in the on state, the potential of the internal ground 11 and the potential of the external ground 21 can be made substantially the same, and the normal operation of the integrated circuit 10 can be continued.

  Thus, even when a ground open occurs, the function terminal 151 can function as a ground terminal. That is, the terminal functioning as the internal ground 11 can be provided in a redundant manner, and fail-safe against the opening of the ground terminal 111 can be easily realized.

The circuit device 1 also includes a switch element Q1 that switches between electrical conduction and interruption between both ends of a diode D1 (ESD protection element 52) that is an impedance element.
As described above, when the switch element Q1 is turned off (at the time of high impedance output), the ground open detection mode in which the ground open can be detected is set. Further, when the switch element Q1 is turned on (at the time of low level output), a fail safe mode with respect to the ground open is set. Therefore, it is possible to easily switch between the ground open detection mode and the fail safe mode only by switching the switch Q1 between on and off. As a result, for example, the ground open detection mode can be set in the normal state, and the normal operation can be continued in the fail safe mode for a certain period when the ground open is detected.

  The ground open detection system 100 includes an external voltage generation circuit 23 that has a plurality of resistors (resistors R1 and R2), generates a second voltage V2 by resistance voltage division, and inputs the second voltage V2 to the voltage input terminal 131. With the above configuration, it is possible to generate the second voltage V2 with the potential of the external ground 21 as a reference with a simple configuration.

  In the example described above, in the functional circuit 5, the output circuit 51 is configured by only the switch element Q1, but the configuration of the output circuit 51 is not limited to the above. Hereinafter, modifications of the output circuit 51 will be described.

  FIG. 2A shows a first modification of the output circuit 51. The output circuit 51 of this modification includes a switch element Q1 made of an n-channel depletion type MOSFET and a switch element Q2 made of a p-channel depletion type MOSFET. The switch element Q2 has a drain and a back gate electrically connected to the power supply wiring 122, a source electrically connected to the function terminal 151, and a gate electrically connected to the second control circuit 25. The switch elements Q1 and Q2 are individually controlled by the second control circuit 25. With the above configuration, the output circuit 51 of this modification can be switched to a high level output, a low level output, or a high impedance output. When the switch elements Q1 and Q2 are turned off and the output circuit 51 is set to high impedance output, the ground open detection mode is set. Further, when the switch element Q1 is turned on, the switch element Q2 is turned off, and the output circuit 51 is set to the low level output, the fail safe mode is set. In the present embodiment, since the function terminal 151 is electrically connected to the external ground, the high level output of the output circuit 51 is not used.

  FIG. 2B shows a second modification of the output circuit 51. The output circuit 51 of this modification includes a switch element Q3 made of an npn-type bipolar transistor and a switch element Q4 made of a pnp-type bipolar transistor. The switch element Q3 has a collector electrically connected to the function terminal 151, a base electrically connected to the second control circuit 25, and an emitter electrically connected to the ground wiring 112. The switch element Q4 has an emitter electrically connected to the power supply wiring 122, a base electrically connected to the second control circuit 25, and a collector electrically connected to the function terminal 151. The switch elements Q3 and Q4 are individually controlled by the second control circuit 25. With the above configuration, the output circuit 51 of this modification can be switched to a high level output, a low level output, or a high impedance output. When the switch elements Q3 and Q4 are turned off and the output circuit 51 is set to high impedance output, the ground open detection mode is set. Further, when the switch element Q3 is turned on, the switch element Q4 is turned off, and the output circuit 51 is set to the low level output, the fail safe mode is set. In the present embodiment, since the function terminal 151 is electrically connected to the external ground, the high level output of the output circuit 51 is not used.

  FIG. 2C shows a third modification of the output circuit 51. The output circuit 51 of this modification is configured by an emitter follower circuit having a switch element Q5 composed of a pnp bipolar transistor and a resistor R3. The switch element Q5 has a collector electrically connected to the power supply wiring 122, a base electrically connected to the second control circuit 25, and an emitter electrically connected to the ground wiring 112 via the resistor R3. In addition, the connection point between the emitter of the switch element Q5 and the resistor R3 is electrically connected to the function terminal 151. The switch element Q5 is controlled by the second control circuit 25. With the above configuration, the output circuit 51 of this modification can be switched between a high level output and a low level output. When the switch element Q5 is turned off and the output circuit 51 is set to the low level output, the ground open detection mode is set. In this case, when a ground open occurs, a current flows from the ground wiring 112 to the external ground 21 via the resistor R3 and the ESD protection element 52, and the potential of the internal ground 11 rises with respect to the potential of the external ground 21. In the present embodiment, since the function terminal 151 is electrically connected to the external ground, the high level output of the output circuit 51 is not used.

  Further, the functional circuit 5 is not limited to the configuration including the output circuit 51, and may be configured to include the input circuit 53 and the ESD protection element 52 as shown in FIG. The input circuit 53 is electrically connected to the ground wiring 112 and further electrically connected to the external ground 21 via a function terminal 151 that functions as an input terminal. The input circuit 53 is configured so that the input impedance becomes high impedance. With the above configuration, when a ground open occurs, a current flows from the ground wiring 112 to the external ground 21 via the ESD protection element 52, and the potential of the internal ground 11 rises with respect to the potential of the external ground 21. Can be detected.

  As shown in FIG. 1, FIG. 2A to FIG. 2C, and FIG. 3, the functional circuit 5 can output high impedance, or an output circuit 51 composed of an emitter follower circuit, or an input circuit 53 whose input impedance is high impedance. It is configured with. A function terminal 151 that is an output terminal of the output circuit 51 or an input terminal of the input circuit 53 is electrically connected to the external ground 21. The functional circuit 5 including the output circuit 51 or the input circuit 53 having such a configuration is generally provided by a general-purpose microcomputer, and the versatility for realizing the circuit device 1 of the present embodiment is further improved. To do.

  As shown in FIGS. 1 and 2A, when the switch element Q1 is composed of an n-channel MOSFET and a parasitic pn junction (parasitic diode) is formed between the drain and source of the switch element Q1, the ESD protection element It is also possible to omit 52. When the ESD protection element 52 is omitted, the parasitic pn junction (parasitic diode) of the switch element Q1 functions as an impedance element.

  Moreover, in the example mentioned above, although the ESD protection element 52 is comprised by the diode D1, it is not limited to this. As shown in FIG. 4, the ESD protection element 52 is configured by a switch element Q6 (impedance element) made of a normally-off type n-channel MOSFET whose gate is electrically connected to the source (ground wiring 112). Good.

  Further, as a modification of the ground open detection system 100, as shown in FIG. 5, a configuration in which a resistor R4 electrically connected between the functional terminal 151 and the external ground 21 may be provided. When a ground open occurs, a current flows from the ground wiring 112 to the external ground 21 via the ESD protection element 52, the function terminal 151, and the resistor R4. When a current flows through the resistor R4, a potential difference is generated between both ends of the resistor R4. Therefore, the potential of the internal ground 11 is higher than the potential of the external ground 21 by the sum of the voltage across the resistor R4 and the threshold voltage of the ESD protection element 52. That is, by providing the resistor R4, it is possible to increase the first voltage V1 when the ground is open. Thereby, before and after the occurrence of the ground open, the difference between the first voltage V1 and the second voltage V2 changes greatly, and the ground open can be easily detected.

  Moreover, in the example mentioned above, although the detection circuit 4 is provided with the conversion circuit 41 and the arithmetic circuit 42, it is not limited to the said structure. FIG. 6 shows a modification of the detection circuit 4. The detection circuit 4 of the present modification includes a comparator 43 that compares the first voltage V1 and the second voltage V2 and detects a ground open based on the magnitude relationship between the first voltage V1 and the second voltage V2. It is configured. The comparator 43 is composed of a comparator, and the first voltage V1 generated by the internal voltage generation circuit 3 is input (applied) to the non-inverting input terminal, and the second voltage generated by the external voltage generation circuit 23 is generated at the inverting input terminal. The voltage V2 is input (applied).

  As described above, when the ground open occurs, the potential of the internal ground 11 rises with respect to the potential of the external ground 21, so that the first voltage V <b> 1 rises with the potential of the external ground 21 as a reference (the above formula) (See (1)). In other words, when a ground open occurs, the second voltage V2 when the potential of the internal ground 11 is used as a reference decreases. Here, the resistance ratio of the resistors R1 and R2 in this modification is such that the second voltage V2 is higher than the first voltage V1 when normal, and the first voltage V1 when the ground is open (referenced to the potential of the external ground 21). Is set to be lower than With the above configuration, the output of the comparator 43 is low level when the ground open is not occurring normally, and the output of the comparator 43 is high level when the ground open is occurring. Thus, by using the comparator 43 that compares the magnitude relationship between the first voltage V1 and the second voltage V2, the output level of the comparator 43 functions as a detection signal indicating whether or not a ground open has occurred, and the detection circuit The configuration of 4 can be simplified.

  In the example described above, the circuit device 1 is configured by enclosing the integrated circuit 10 formed on the chip in a package. However, as shown in FIGS. The unit may be provided outside the integrated circuit 10.

  In the example shown in FIG. 7, the detection circuit 4 is provided on the circuit board 2, and the first voltage V <b> 1 generated by the internal voltage generation circuit 3 is applied to the detection circuit 4 via the voltage output terminal 171 of the integrated circuit 10. Is output. The second voltage V <b> 2 generated by the external voltage generation circuit 23 provided on the circuit board 2 is output to the detection circuit 4 via the conductor pattern formed on the circuit board 2. The configuration of the detection circuit 4 may be a configuration including the conversion circuit 41 and the arithmetic circuit 42 (see FIG. 1) or a configuration including the comparator 43 (see FIG. 6).

  In the example shown in FIG. 8, the conversion circuit 41 of the detection circuit 4 is provided in the integrated circuit 10, and the arithmetic circuit 42 is provided in the circuit board 2. Then, the conversion circuit 41 converts the first voltage V1 and the second voltage V2 into digital values and outputs them to the arithmetic circuit 42 via the output terminal 181.

  As described above, the circuit device 1 can detect a ground open even when all or part of the detection circuit 4 is provided outside the integrated circuit 10.

  The above-described embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and various modifications can be made according to design and the like as long as the technical idea according to the present invention is not deviated from this embodiment. Of course, it can be changed.

DESCRIPTION OF SYMBOLS 1 Circuit apparatus 100 Ground open detection system 111 Ground terminal 131 Voltage input terminal 151 Function terminal 21 External ground 23 External voltage generation circuit 3 Internal voltage generation circuit 4 Detection circuit 41 Conversion circuit 42 Operation circuit 43 Comparator 5 Function circuit D1 Diode (impedance element)
Q1, Q3 switch element Q6 switch element (impedance element)

Claims (7)

A ground terminal configured to be electrically connectable to an external ground; and
An internal voltage generation circuit for generating a first voltage based on the potential of the ground terminal;
A voltage input terminal configured to be able to input a second voltage based on the potential of the external ground;
A circuit device comprising: a detection circuit configured to detect a ground open in which the ground terminal and the external ground are not electrically connected based on the first voltage and the second voltage. The detection circuit includes:
A conversion circuit that converts the first voltage and the second voltage into a digital value and outputs the digital value;
The circuit device according to claim 1, further comprising: an arithmetic circuit that detects the ground open based on a difference between the first voltage and the second voltage output from the conversion circuit. The detection circuit includes a comparator that compares the first voltage with the second voltage and detects the ground open based on a magnitude relationship between the first voltage and the second voltage. The circuit device according to claim 1. A functional terminal configured to be electrically connectable to the external ground;
The circuit device according to claim 1, further comprising an impedance element electrically connected between the ground terminal and the functional terminal. The circuit device according to claim 4, further comprising a switch element that switches between electrical conduction and interruption between both ends of the impedance element. A circuit device according to claim 4 or 5,
A ground open detection system comprising: the external ground electrically connected to the functional terminal. The ground open detection system according to claim 6, further comprising an external voltage generation circuit that has a plurality of resistors, generates the second voltage by resistance voltage division, and inputs the second voltage to the voltage input terminal.

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