JP2011089850A - Wire break detecting and reverse connection protecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wire break detecting and reverse connection protecting apparatus for restraining the manufacturing cost, when attaining actualization of a wire breaking detecting function, and moreover, protecting circuit element, when a power supply line and a ground line are connected in reverse. <P>SOLUTION: According to the wire break detector/reverse connection protector, a wire break in a ground line 50 is detected among a power supply line 30, the ground line 50 and a signal line 40 for connecting a sensor circuit 10A and a control circuit 20, and the circuits are protected from a reverse connection of the supply line 30 and the ground line 50. A pull-down resistor R101 is connected between the signal line 40 and the ground line 50. A wire-break detecting circuit 103 makes the electric potential of the signal line 40 rise to the vicinity of the power supply potential of the supply line 30, when the ground line 50 is broken; and further, when the supply line 30 and the ground line 50 are connected in reverse, a reverse connection protecting circuit 104 disconnects the supply line 30 from the detecting circuit 103 and disconnects the supply line 30 from a sensor 101 and a functional circuit 102A. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a disconnection detection / reverse connection protection device that detects disconnection of a power supply line, a ground line, and a signal line connected to each circuit and protects the circuit from reverse connection of the power supply line and the ground line.

FIG. 9 is a block diagram illustrating an example of a configuration of a conventional sensor device to which this type of disconnection detection device is applied.
As shown in FIG. 9, the sensor device includes a sensor circuit 10 and a control circuit 20 that processes an output signal from the sensor circuit 10 and supplies a power supply voltage to the sensor circuit 10. The sensor circuit 10 and the control circuit 20 are connected to each other via a power line 30, a signal line 40, and a ground line 50.

The sensor circuit 10 includes a sensor 101 and a functional circuit 102 such as an amplification processing unit that internally processes an output signal from the sensor 101 and outputs the processed signal to the control circuit 20.
The control circuit 20 is connected between a power supply circuit 201 that generates a power supply voltage for driving the sensor circuit 10, an AD conversion circuit 202 that processes an output signal from the sensor circuit 10, and an input terminal Vin and a ground terminal GND. Pull-down resistor R201.

FIG. 10 is a circuit diagram of an amplification processing unit which is a part of the functional circuit 102 of FIG. 9 and includes a conventional disconnection detection circuit (see Patent Document 1).
The amplification processing unit includes an operational amplifier OP3, a resistor Ra, and the like, and performs amplification processing of an output signal from the sensor 101.
The amplification processing unit is for the differential amplifier circuit A1, the diode D1, the bias circuit B1 as a current control circuit for driving the differential amplifier circuit A1, the output side amplifier circuit A2, and the output side amplifier circuit A2. Current control circuit S1 and a constant current circuit S2 for supplying current to an output current source composed of transistors Tr15 and Tr16, and detects disconnection together with pull-down resistor R201.

  Here, the differential amplifier circuit A1 includes transistors Tr1 to Tr7 and the like. The output side amplifier circuit A2 includes transistors Tr8, Tr14, and the like. The bias circuit B1 includes transistors Tr9 and Tr10. The current control circuit S1 includes transistors Tr12, Tr13, and the like. The constant current circuit S2 includes transistors Tr17 and Tr18.

Next, the operation of the amplification processing unit configured as described above will be described.
As shown in FIG. 9, when the external ground line 50 is disconnected while the pull-down resistor R201 is connected between the input terminal Vin of the control circuit 20 and the ground terminal GND, a current is applied to the ground line Vc2 of FIG. Current flows, the current does not flow into the transistors Tr1, Tr2, Tr6, Tr7 because the diode D1 is reversely connected.

Further, since the current control circuit S1 cuts off the collector current of the transistor Tr8, the output side amplification circuit A2 and the transistor Tr15 do not function, and no current flows out from the output terminal Vout. Therefore, disconnection can be detected without causing a voltage drop by the pull-down resistor R201.
However, if a parasitic element exists in the elements such as the transistors Tr1 to Tr17 constituting the amplification processing unit described above, the parasitic element becomes a bypass path such as the backflow prevention means D1 and the current prevention means Tr11, and inhibits the function of the prevention means. There is a case.

For example, in the transistor Tr11, when there is a parasitic diode having the silicon P substrate as an anode and the base region of the transistor Tr11 as a cathode, the disconnection detection function is hindered.
In this case, when an oxide film insulating isolation structure is formed on an SOI (Silicon On Insulator) substrate in the configuration of the transistor, the parasitic element does not exist, but the manufacturing cost increases.
On the other hand, in the sensor device shown in FIG. 9, in addition to the function of detecting the disconnection of the ground line 50, the sensor circuit 10A is reversely connected when the power line 30 and the ground line 50 are erroneously reversely connected. The emergence of a new device having a function of protecting from the development is desired.

JP 2004-301670 A

  Accordingly, an object of the present invention is to provide a disconnection detection / reverse connection protection device capable of reducing the manufacturing cost when realizing a disconnection function and protecting circuit elements when a power supply line and a ground line are reversely connected. Is to provide.

In order to solve the above-described problems and achieve the object of the present invention, each invention has the following configuration.
1st invention detects the disconnection of the said ground line among the power supply line which connects each circuit mutually, a ground line, and a signal line, and the disconnection which protects each said circuit from the reverse connection of the said power supply line and a ground line A detection / reverse connection protection device comprising: a pull-down resistor provided between the signal line and the ground line; and connecting the power line and the signal line when the ground line is disconnected; A first switch that raises near the power supply potential of the power supply line; and the power supply line and each circuit are connected when the power supply line and the ground line are normally connected; and the power supply line and each circuit are connected when the reverse connection is established A second switch for disconnecting the power supply line, and a third switch for connecting the power supply line and the first switch during the normal connection and disconnecting the connection between the power supply line and the first switch during the reverse connection. That.

In a second aspect based on the first aspect, the first switch is a first NMOS transistor, the second switch is a PMOS transistor, and the third switch is a second NMOS. It is a transistor.
According to a third invention, in the second invention, the second NMOS transistor is formed in the P well by forming a P well with an N well interposed in a P type substrate.

  In a fourth aspect based on the second or third aspect, the first NMOS transistor has a source connected to the signal line, a gate and a substrate connected to the ground line, and a drain connected to the second NMOS. The PMOS transistor has a source connected to the power supply line, a gate connected to the ground line, a drain and a substrate connected to an internal power supply terminal of the circuit, and the second NMOS transistor. The source is connected to the drain of the first NMOS transistor, and the gate, drain and substrate are connected to the power line.

In a fifth aspect based on the second to fourth aspects, the first and second NMOS transistors and the PMOS transistor are formed on the same P-type substrate.
In a sixth aspect based on the first to fifth aspects, each of the circuits includes a sensor circuit and a control circuit, and the control circuit generates a power supply voltage for driving the sensor circuit and from the sensor circuit. Process the output signal.

  According to the present invention having such a configuration, it is possible to reduce the manufacturing cost when realizing the disconnection function, and to protect the circuit element when the power supply line and the ground line are reversely connected. Can do.

It is a block diagram which shows the structure of the sensor apparatus to which 1st Embodiment of this invention apparatus is applied. It is sectional drawing which shows the cross-section of the transistor applied to the disconnection detection circuit and reverse connection protection circuit of 1st Embodiment. It is a block diagram which shows the structure of the sensor apparatus to which 2nd Embodiment of this invention apparatus is applied. It is sectional drawing which shows the cross-section of the transistor applied to the disconnection detection circuit and reverse connection protection circuit of 2nd Embodiment. It is a block diagram which shows the structure of the sensor apparatus to which 3rd Embodiment of this invention apparatus is applied. It is sectional drawing which shows sectional structure of the transistor etc. which are applied to the disconnection detection circuit and reverse connection protection circuit of 3rd Embodiment. It is a block diagram which shows the structure of the sensor apparatus to which 4th Embodiment of this invention apparatus is applied. It is sectional drawing which shows the cross-section of the transistor applied to the disconnection detection circuit and reverse connection protection circuit of 4th Embodiment. It is a block diagram which shows the structure of the conventional sensor apparatus. FIG. 6 is a circuit diagram of an amplification processing unit including a conventional disconnection detection circuit.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram in which a first embodiment of the device of the present invention is applied to a sensor device.
As shown in FIG. 1, the sensor device includes a sensor circuit 10A and a control circuit 20. The sensor circuit 10A is driven by a power supply voltage supplied from the control circuit 20, and the output signal of the sensor circuit 10A is a control circuit. 20 to be processed. Therefore, in the sensor device, the sensor circuit 10 </ b> A and the control circuit 20 are connected to each other via the power supply line 30, the signal line (output line) 40, and the ground line 50.

Further, this sensor device detects the disconnection when any one of the power supply line 30, the signal line 40, and the ground line 50 is disconnected, and when the power supply line 30 and the ground line 50 are reversely connected, The components of the sensor 101 and the functional circuit 102A of the sensor circuit 10A are protected from destruction.
As shown in FIG. 1, the sensor circuit 10A includes a sensor 101, a functional circuit 102A, a disconnection detection circuit 103, a reverse connection protection circuit 104, a power supply terminal Vcc, an output terminal Vout, and a ground terminal GND. ing.

The sensor 101 converts a predetermined physical quantity or the like into an electrical signal and outputs it. The functional circuit 102A internally processes an output signal from the sensor 101 and outputs it to the control circuit 20, and is composed of, for example, an amplification processing unit. Further, the sensor 101 and the functional circuit 102A are protected by the reverse connection protection circuit 104 when the power supply line 30 and the ground line 50 are reversely connected.
For this reason, the sensor 101 and the functional circuit 102A are connected to the power supply terminal Vcc through the reverse connection protection circuit 104 and are also connected to the ground terminal GND, and from the control circuit 20 through the power supply line 30 and the reverse connection protection circuit 104. Driven by the power supply voltage supplied. The output signal of the functional circuit 102A is output to the output terminal Vout and input to the input terminal Vin of the control circuit 20 via the signal line 40.

  When the ground line 50 is disconnected, the disconnection detection circuit 103 is linked to the pull-down resistor R101 and the like, and the output potential of the output terminal Vout of the sensor circuit 10A (the potential of the signal line 40) is set to the power supply terminal Vcc (power supply line 30). Raise to near electric potential to fix or maintain the state. In other words, when the ground line 50 is disconnected, the disconnection detection circuit 103 is linked with the pull-down resistor R101 and the like, and changes the potential of the input terminal Vin of the control circuit 20 to the vicinity of the potential of the power supply voltage Vcc. Let the state be fixed or maintained.

  For this reason, the disconnection detection circuit 103 is configured by an N-type MOS transistor Tr101 that functions as a switch element. The MOS transistor Tr101 has a drain connected to the source of a MOS transistor Tr202 described later, a source connected to the output terminal Vout, and a gate and a substrate (body terminal) connected to the ground terminal GND. The MOS transistor Tr101 includes parasitic diodes D101 and D102 as shown in FIGS.

  The reverse connection protection circuit 104 performs connection between the power supply line 30, the sensor 101, and the functional circuit 102A when the power supply line 30 and the ground line 50 are normally connected, and also connects the power supply line 30 and the disconnection detection circuit 103. Do. The reverse connection protection circuit 104 disconnects the connection between the power supply line 30 and the sensor 101 and the functional circuit 102A and connects the power supply line 30 and the disconnection detection circuit 103 when the power supply line 30 and the ground line 50 are reversely connected. Disconnect.

  Therefore, the reverse connection protection circuit 104 includes a P-type MOS transistor Tr201 and an N-type MOS transistor Tr202 that function as switch elements. The P-type MOS transistor Tr201 connects and disconnects the power supply line 30, the sensor 101, and the functional circuit 102A. The N-type MOS transistor Tr202 connects and disconnects the power supply line 30 and the disconnection detection circuit 103.

The MOS transistor Tr201 has a source connected to the power supply terminal Vcc, a gate connected to the ground terminal GND, and a drain and a substrate (body terminal) connected to the sensor 101 and the power supply terminal N201 of the functional circuit 102. Further, the MOS transistor Tr201 includes a parasitic diode D201 as shown in FIGS.
The MOS transistor Tr202 has a gate, a drain, and a substrate (body terminal) connected to the power supply terminal Vcc, and a source connected to the drain of the MOS transistor Tr101. Further, the MOS transistor Tr202 includes a parasitic diode D202 as shown in FIGS.

As shown in FIG. 1, the control circuit 20 includes a power supply circuit 201, an AD conversion circuit 202, a pull-down resistor R101, a power supply terminal Vcc, an input terminal Vin, and a ground terminal GND.
The power supply circuit 201 generates power supply voltages for driving the sensor circuit 10A and the AD conversion circuit 202, respectively. The generated power supply voltage is supplied to the sensor circuit 10 </ b> A via the power supply line 30.

The AD conversion circuit 202 is driven by the power supply voltage generated by the power supply circuit 201, AD converts the analog signal output from the sensor circuit 10A into a digital signal, and outputs the digital signal. Therefore, the AD conversion circuit 202 is connected to the power supply circuit 201, the input terminal Vin, and the ground terminal GND.
The pull-down resistor R101 is provided between the input terminal Vin and the ground terminal GND, and is connected therebetween. As will be described later, the pull-down resistor R101 contributes to the disconnection detection function in conjunction with the disconnection detection circuit 103.

FIG. 2 is a cross-sectional view showing a cross-sectional structure of the N-type MOS transistor Tr101 used in the disconnection detection circuit 103, the P-type MOS transistor Tr201 and the N-type MOS transistor Tr202 used in the reverse connection protection circuit 104. is there.
These three MOS transistors Tr101, Tr201, Tr202 are configured using the same P-type substrate 600 of silicon as shown in FIG.

First, the MOS transistor Tr101 is formed in a P well 601 provided in a P type substrate 600. That is, an N + region 602 serving as a source region and an N + region 603 serving as a drain region are formed in the P well 601. A gate 604 is formed on the P well 601 with an insulator interposed therebetween.
Further, the N + region 602 serving as the source region is connected to the output terminal Vout, the N + region 603 serving as the drain region is connected to the N + region 622 serving as the source region of the MOS transistor Tr202, and the gate 604 is connected to the ground terminal GND. . The P-type substrate 600 and the P well 601 are each connected to the ground terminal GND.

  In the N-type MOS transistor Tr101 having such a configuration, parasitic diodes D101 and D102 as shown in FIG. 2 are formed. That is, the parasitic diode D101 uses the P well 601 (P-type substrate 600) as an anode and the N + region 602 serving as a source region as a cathode. The parasitic diode D102 uses the P well 601 as an anode and the N + region 603 serving as a drain region as a cathode.

Next, the MOS transistor Tr 201 is formed in an N well 611 provided in the P-type substrate 600. That is, a P + region 612 serving as a source region and a P + region 613 serving as a drain region are formed in the N well 611. A gate 614 is formed on the N well 611 with an insulator interposed therebetween.
Further, the P + region 612 serving as the source region is connected to the power supply terminal Vcc, the P + region 613 serving as the drain region and the N well 611 are connected to the power supply terminal N201 of the sensor 101 and the functional circuit 102, and the gate 614 is connected to the ground terminal GND. Connected.

In the P-type MOS transistor Tr201 having such a configuration, a parasitic diode D201 as shown in FIG. 2 is formed. In other words, the parasitic diode D201 uses the P + region 612 serving as the source region as an anode and the N well 611 as a cathode.
Next, the MOS transistor Tr202 is formed in the P-type substrate 600 by forming the P-well 621 through the N-well 620 and separating it from the P-type substrate 600 by the N-well 620.

That is, an N + region 622 serving as a source region and an N + region 623 serving as a drain region are formed in the P well 621. A gate 624 is formed on the P well 621 with an insulator interposed therebetween.
Further, the N + region 622 serving as the source region is connected to the N + region 603 serving as the drain region of the MOS transistor Tr101, and the N + region 623, the gate 624, and the P well 621 serving as the drain region are respectively connected to the output terminal Vout.
In the N-type MOS transistor Tr202 having such a configuration, a parasitic diode D202 as shown in FIG. 2 is formed. That is, the parasitic diode D202 uses the P well 621 as an anode and the N + region 622 serving as a source region as a cathode.

Next, an operation example of the reverse connection protection circuit 104 according to the first embodiment configured as described above will be described with reference to FIG.
First, when the power supply line 30 and the ground line 50 are reversely connected (when the power supply is reversely connected), that is, the power supply line 30 is connected to the power supply terminal Vcc of the control circuit 20 and the ground terminal GND of the sensor circuit 10A. This is a case where the line 50 is connected to the ground terminal GND of the control circuit 20 and the power supply terminal Vcc of the sensor circuit 10A.
In this case, the P-type MOS transistor Tr201 is turned off because the gate voltage becomes high with reference to the source voltage. For this reason, since the electrical connection between the power supply terminal Vcc and the sensor 101 and the power supply terminal N201 of the functional circuit 102A is released, the current is prevented from flowing into the sensor 101 and the functional circuit 102A from the ground terminal GND. As a result, the sensor 101 and the functional circuit 102A are protected from destruction of circuit elements.

On the other hand, the N-type MOS transistor Tr202 is turned off because the gate voltage is low with respect to the source voltage. Therefore, the MOS transistor Tr101 of the disconnection detection circuit 103 cannot be turned on, and a through current is prevented from flowing from the ground terminal GND to the power supply terminal Vcc via the disconnection detection circuit 103.
When the power supply line 30 and the ground line 50 are reversely connected, since the parasitic diodes D201 and D202 are reversely biased, they are turned off, and the above-described reverse connection protection operation is not hindered.

Next, the operation when the power supply line 30 and the ground line 50 are correctly connected as shown in FIG. 1 (during normal connection) will be described.
In this case, the P-type MOS transistor Tr201 is turned on because the gate voltage is lowered with reference to the source voltage. Therefore, a current flows from the power supply terminal Vcc to the power supply terminal N201 of the sensor 101 and the functional circuit 102A via the MOS transistor Tr201, and the potential of the power supply terminal N201 becomes close to the potential of the power supply terminal Vcc. As a result, the sensor 101 and the functional circuit 102A operate normally.

  On the other hand, the N-type MOS transistor Tr202 is turned on because the gate potential becomes higher with reference to the source potential. Therefore, current flows from power supply terminal Vcc to node N204, and the potential of node N204 is close to the potential of power supply terminal Vcc. As a result, the MOS transistor Tr101 of the disconnection detection circuit 103 is turned off because the gate voltage becomes low with respect to the source voltage, and no current flows from the power supply terminal Vcc to the output terminal Vout.

Next, as shown in FIG. 1, an operation example of disconnection detection of the disconnection detection circuit 103 or the like when the power supply line 30 and the ground line 50 are correctly connected and the sensor 101 and the functional circuit 102A are operating normally will be described with reference to FIG. Will be described with reference to FIG.
Now, it is assumed that the ground line 50 is disconnected while the pull-down resistor R101 is connected between the input terminal Vin of the control circuit 20 and the ground terminal GND. In this case, a current flows from the power supply terminal Vcc to the ground line N202 in the sensor circuit 10A via the MOS transistor Tr201, the sensor 101, and the functional circuit 102A, and the potential of the ground line N202 increases.

  For this reason, the MOS transistor Tr101 is turned on because the gate voltage becomes higher with reference to the source voltage. At this time, since the MOS transistor Tr202 is also in the on state, a current flows from the power supply terminal Vcc to the output terminal Vout via the MOS transistors Tr202 and Tr101. Then, the potential of the input terminal Vin of the control circuit 20, that is, the input potential of the AD conversion circuit 202 rises to the vicinity of the potential of the power supply terminal Vcc and is fixed in that state.

  As described above, when the ground line 50 is disconnected, the potential of the input terminal Vin of the control circuit 20 is in the vicinity of the potential of the power supply terminal Vcc of the sensor circuit 10A, that is, the power supply by the linked operation of the MOS transistor Tr101 and the pull-down resistor R101. The voltage rises to a value near the power supply voltage generated by the circuit 201 and is fixed. For this reason, for example, the control circuit 20 can recognize the presence or absence of the disconnection of the ground line 50 by monitoring (detecting) the input voltage of the input terminal Vin.

  When the ground line 50 is disconnected, the parasitic diode D101 of the MOS transistor Tr101 is forward-biased, so that no current flows from the output terminal Vout to the ground line N202 via the parasitic diode D101. Further, since the parasitic diode D102 is biased in the reverse direction, the parasitic diode D102 is turned off, and no current flows from the ground line N202 to the power supply terminal Vcc. Therefore, the parasitic diodes D101 and D102 do not hinder the disconnection detection operation of the ground line 50.

Next, an operation when the power supply line 30 is disconnected will be described.
In this case, since the supply of the power supply voltage generated by the power supply circuit 201 of the control circuit 20 to the sensor circuit 10A is stopped, the sensor 101, the functional circuit 102A, and the MOS transistors Tr101, Tr201, Tr202 become inoperable. However, the potential of the input terminal Vin of the control circuit 20 changes near the potential of the ground terminal GND by the pull-down resistor R101 and is fixed in the state after the change.
The parasitic diodes D101 and D102 are turned off and do not hinder the disconnection detection operation.

Next, an operation when the signal line 40 is disconnected will be described.
In this case, the sensor 101 and the functional circuit 102A operate normally because the power supply line 30 and the ground line 50 are normal. Further, since the MOS transistor Tr101 is turned off, the operation of the sensor 101 and the functional circuit 102A is not hindered.
On the other hand, the output signal of the functional circuit 102 </ b> A is not transmitted to the input terminal Vin of the control circuit 20 via the signal line 40. However, the potential of the input terminal Vin of the control circuit 20 changes near the potential of the ground terminal GND by the pull-down resistor R101 and is fixed in the state after the change.
The parasitic diodes D101 and D102 are turned off and do not hinder the disconnection detection operation.

  Thus, when the power supply line 30 or the signal line 40 is disconnected, the potential of the input terminal Vin of the control circuit 20 changes to a value in the vicinity of the potential of the ground terminal GND, and is fixed in the state after the change. The For this reason, for example, the control circuit 20 can recognize the presence or absence of disconnection of the power supply line 30 or the signal line 40 by monitoring (detecting) the input voltage of the input terminal Vin.

As described above, according to the first embodiment, when the power supply line 30 and the ground line 50 are reversely connected, it is possible to protect the sensor 101 and the functional circuit 102A from being destroyed and to prevent a through current in the disconnection detection circuit 103.
In the first embodiment, when the ground line 50 is disconnected while the power supply line 30 and the ground line 50 are correctly connected and operate normally, the linked operation of the MOS transistor Tr101 and the pull-down resistor R101 is performed. Thus, the disconnection can be detected.

(Second Embodiment)
FIG. 3 is a block diagram in which the second embodiment of the disconnection detection device of the present invention is applied to a sensor device.
This sensor device is basically the same as the configuration of the sensor device in FIG. 1, and is obtained by replacing the reverse connection protection circuit 104 in FIG. 1 with a reverse connection protection circuit 104A in FIG. For this reason, the same components are denoted by the same reference numerals, description thereof is omitted, and the configuration and operation of the reverse connection protection circuit 104A will be mainly described.
The reverse connection protection circuit 104A functions in the same manner as the reverse connection protection circuit 104 in FIG. 1, and is obtained by replacing the MOS transistor Tr201 in FIG. 1 with a PNP-type bipolar transistor Tr203 and a resistor R202 in FIG.

The bipolar transistor Tr203 has an emitter connected to the power supply terminal Vcc, a base connected to the ground terminal GND via the resistor R202, and a collector connected to the sensor 101 and the power supply terminal N201 of the functional circuit 102.
FIG. 4 is a cross-sectional view showing a cross-sectional structure of the N-type MOS transistor Tr101 used in the disconnection detection circuit 103, the PNP-type bipolar transistor Tr203 and the N-type MOS transistor Tr202 used in the reverse connection protection circuit 104A. is there.

As shown in FIG. 4, these three transistors Tr101, Tr203, Tr202 are configured using the same silicon P-type substrate 600, and the transistors Tr101, Tr202 are configured in the same manner as in FIG. Therefore, the same components are denoted by the same reference numerals, and the description thereof is omitted, and the configuration of the bipolar transistor Tr203 will be described.
The bipolar transistor Tr203 is surrounded by P-type isolation layers 631 and 632 and an N-type buried layer 633 in the P-type substrate 600 to form an N-type base region 634 serving as a base region. In the N-type base region 634, a P-type emitter region 635 serving as an emitter region and a P-type collector region 636 serving as a collector region are formed.
The P-type emitter region 635 is connected to the power supply terminal Vcc, the P-type collector region 636 is connected to the power supply terminal N201 of the sensor 101 and the functional circuit 102, and the N-type base region 634 is connected to the ground terminal GND via the resistor R202. Connected.

Next, an operation example of the reverse connection protection circuit 104A of the second embodiment configured as described above will be described with reference to FIG.
First, the operation when the power supply line 30 and the ground line 50 are reversely connected will be described.
In this case, since the base voltage of the bipolar transistor Tr203 becomes higher with reference to the collector voltage, the bipolar transistor Tr203 is turned off. For this reason, since the electrical connection between the power supply terminal Vcc and the sensor 101 and the power supply terminal N201 of the functional circuit 102A is released, the current is prevented from flowing into the sensor 101 and the functional circuit 102A from the ground terminal GND. As a result, the sensor 101 and the functional circuit 102A are protected from destruction of circuit elements.

On the other hand, the N-type MOS transistor Tr202 operates in the same manner as in the first embodiment and is turned off, so that a through current does not flow through the MOS transistor Tr101 of the disconnection detection circuit 103.
When the power supply line 30 and the ground line 50 are reversely connected, since the parasitic diode D202 is reverse-biased, they are turned off, and the reverse connection protection operation is not hindered.

Next, a case where the power supply line 30 and the ground line 50 are normally connected as shown in FIG. 3 will be described.
In this case, since the base voltage of the bipolar transistor Tr203 becomes lower with reference to the collector voltage, the bipolar transistor Tr203 is turned on. For this reason, current flows from the power supply terminal Vcc to the power supply terminal N201 of the sensor 101 and the functional circuit 102A via the bipolar transistor Tr203, and the potential of the power supply terminal N201 becomes close to the potential of the power supply terminal Vcc. As a result, the sensor 101 and the functional circuit 102A operate normally.
On the other hand, since the N-type MOS transistor Tr202 operates and is turned on in the same manner as in the first embodiment, the MOS transistor Tr101 is turned off and no current flows from the power supply terminal Vcc to the output terminal Vout. .
As mentioned above, according to 2nd Embodiment, the effect similar to 1st Embodiment is realizable.

(Third embodiment)
FIG. 5 is a block diagram in which the third embodiment of the disconnection detection device of the present invention is applied to a sensor device.
This sensor device is basically the same as the configuration of the sensor device in FIG. 1, and is obtained by replacing the reverse connection protection circuit 104 in FIG. 1 with a reverse connection protection circuit 104B in FIG. For this reason, the same components are denoted by the same reference numerals, description thereof is omitted, and the configuration and operation of the reverse connection protection circuit 104B will be mainly described.
The reverse connection protection circuit 104B functions in the same manner as the reverse connection protection circuit 104 in FIG. 1, and is obtained by replacing the MOS transistor Tr201 in FIG. 1 with a diode D203 in FIG.
The diode D203 has an anode side connected to the power supply terminal Vcc and a cathode side connected to the sensor 101 and the power supply terminal N201 of the functional circuit 102A.
FIG. 6 is a cross-sectional view showing a cross-sectional structure of an N-type MOS transistor Tr101 used in the disconnection detection circuit 103, and a diode D203 and an N-type MOS transistor Tr202 used in the reverse connection protection circuit 104B.

As shown in FIG. 6, the transistors Tr101 and Tr202 and the diode D203 are configured using the same silicon P-type substrate 600, and the transistors Tr101 and Tr202 are configured in the same manner as in FIG. Therefore, the same components are denoted by the same reference numerals, and the description thereof is omitted, and the configuration of the diode D203 will be described.
As shown in FIG. 6, the diode D203 forms an N-well 641 in a P-type substrate 600, and uses the N-well 641 as a cathode. Further, a P + region 642 is formed in the N well 641, and this is used as an anode. P + region 642 is connected to power supply terminal Vcc, and N well 641 is connected to sensor 101 and power supply terminal N201 of functional circuit 102A.

Next, an operation example of the reverse connection protection circuit 104B of the third embodiment configured as described above will be described with reference to FIG.
First, the operation when the power supply line 30 and the ground line 50 are reversely connected will be described.
In this case, the diode D203 is in a reverse bias state and is turned off. For this reason, since the electrical connection between the power supply terminal Vcc and the power supply terminal N201 is released, current is prevented from flowing into the sensor 101 and the functional circuit 102A from the ground terminal GND. As a result, the sensor 101 and the functional circuit 102A are protected from destruction of circuit elements.

On the other hand, the N-type MOS transistor Tr202 operates in the same manner as in the first embodiment and is turned off, so that a through current does not flow through the MOS transistor Tr101 of the disconnection detection circuit 103.
When the power supply line 30 and the ground line 50 are reversely connected, since the parasitic diode D202 is reverse-biased, they are turned off, and the reverse connection protection operation is not hindered.

Next, a case where the power supply line 30 and the ground line 50 are correctly connected as shown in FIG. 5 will be described.
In this case, the diode D203 is in a forward bias state and is turned on. Therefore, current flows from the power supply terminal Vcc to the sensor 101 and the power supply terminal N201 of the functional circuit 102A via the diode D203, and the potential of the power supply terminal N201 becomes close to the potential of the power supply terminal Vcc. As a result, the sensor 101 and the functional circuit 102A operate normally.
On the other hand, since the N-type MOS transistor Tr202 operates and is turned on in the same manner as in the first embodiment, the MOS transistor Tr101 is turned off and no current flows from the power supply terminal Vcc to the output terminal Vout. .
As described above, according to the third embodiment, it is possible to achieve the same operational effects as those of the first embodiment.

(Fourth embodiment)
FIG. 7 is a block diagram in which the fourth embodiment of the disconnection detection device of the present invention is applied to a sensor device.
This sensor device is basically the same as the configuration of the sensor device in FIG. 1, and is obtained by replacing the disconnection detection circuit 103 in FIG. 1 with a disconnection detection circuit 103A in FIG. For this reason, the same components are denoted by the same reference numerals, description thereof is omitted, and the configuration and operation of the disconnection detection circuit 103A will be mainly described.
The disconnection detection circuit 103A functions in the same manner as the disconnection detection circuit 103 in FIG. 1, and is obtained by replacing the MOS transistor Tr101 in FIG. 1 with an NPN bipolar transistor Tr102 in FIG.

FIG. 8 is a cross-sectional view showing a cross-sectional structure of the bipolar transistor Tr102 used in the disconnection detection circuit 103A and the MOS transistors Tr201 and Tr202 used in the reverse connection protection circuit 104.
As shown in FIG. 8, these transistors Tr102, Tr201, Tr202 are configured using the same silicon P-type substrate 600, and the transistors Tr201, Tr202 are configured in the same manner as in FIG. Therefore, the same components are denoted by the same reference numerals, and the description thereof is omitted, and the configuration of the bipolar transistor Tr102 will be described.

  As shown in FIG. 8, the transistor Tr102 is surrounded by P-type isolation layers 651 and 652 and an N-type buried layer 653 in a P-type substrate 600, and an N-type collector region 654 serving as a collector region is formed. . Further, a P-type base region 655 serving as a base region is formed in the N-type collector region 654. Further, an N-type emitter region 656 serving as an emitter region is formed in the P-type base region 655.

  The N-type collector region 654 is connected to the N + region 622 that is the source region of the MOS transistor Tr202, the N-type emitter region 656 is connected to the output terminal Vout, and the P-type base region 655 is connected to the ground terminal GND. In the transistor Tr102 having such a configuration, a parasitic diode D103 as shown in FIG. 8 is formed. That is, the parasitic diode D103 has the P-type substrate 600 as an anode and the N-type collector region 654 as a cathode.

Next, an operation example of disconnection detection based on the disconnection detection circuit 103A of the fourth embodiment configured as described above will be described with reference to FIG.
As shown in FIG. 7, when the ground line 50 is disconnected in a state where the power line 30 and the ground line 50 are correctly connected and the pull-down resistor R101 is connected between the input terminal Vin and the ground terminal GND of the control circuit 20. Will be described.
In this case, a current flows from the power supply terminal Vcc to the ground line N202 in the sensor circuit 10A via the MOS transistor Tr201, the sensor 101, and the functional circuit 102A, and the potential of the ground line N202 increases.

  For this reason, the transistor Tr102 is turned on because the base voltage becomes higher with reference to the emitter voltage. At this time, since the MOS transistor Tr202 is also in the on state, a current flows from the power supply terminal Vcc to the output terminal Vout via the transistors Tr202 and Tr102. Then, the potential of the input terminal Vin of the control circuit 20, that is, the input potential of the AD conversion circuit 202 rises near the potential of the power supply terminal Vcc and is fixed in that state.

  Thus, when the ground line 50 is disconnected, the potential of the input terminal Vin of the control circuit 20 is near the potential of the power supply terminal Vcc of the sensor circuit 10A, that is, the power It becomes a value in the vicinity of the power supply voltage generated by the circuit 201. For this reason, for example, the control circuit 20 can recognize whether or not the ground line 50 is disconnected by monitoring the input voltage of the input terminal Vin.

Since the parasitic diode D103 is biased in the reverse direction when the ground line 50 is disconnected, the parasitic diode D103 is turned off, and no current flows from the ground line N202 to the power supply terminal Vcc. Therefore, the parasitic diode D103 does not hinder the disconnection detection operation of the ground line 50.
Here, when the power supply line 30 or the signal line 40 is disconnected, the potential of the input terminal Vin of the control circuit 20 becomes a value near the potential of the ground terminal GND as in the case of the first embodiment. For this reason, for example, the control circuit 20 can recognize the presence or absence of disconnection of the power supply line 30 or the signal line 40 by monitoring (detecting) the input voltage of the input terminal Vin.

  As in the case of the sensor device described above, the device of the present invention connects a first circuit such as a sensor circuit and a second circuit such as a control circuit to each other by a power supply line, a ground line, and a signal line. It can be applied to various devices and systems.

10A ... sensor circuit 20 ... control circuit 30 ... power supply line 40 ... signal line (output line)
50 ... Ground line 101 ... Sensor 102A ... Functional circuit 103, 103A ... Disconnection detection circuit 104, 104A to 104C ... Reverse connection protection circuit R101 ... Pull-down resistor

Claims (6)

Disconnection detection / reverse connection protection device for detecting disconnection of the ground line among power supply lines, ground lines, and signal lines connecting the circuits to each other and protecting the circuits from reverse connection of the power supply line and the ground line Because
A pull-down resistor provided between the signal line and the ground line;
A first switch that connects the power line and the signal line when the ground line is disconnected, and raises the potential of the signal line to near the power supply potential of the power line;
A second switch that connects the power line and the circuits when the power line and the ground line are normally connected, and disconnects the power line and the circuits when the connection is reverse;
A third switch that connects the power supply line and the first switch during the normal connection and disconnects the connection between the power supply line and the first switch during the reverse connection;
A disconnection detection / reverse connection protection device comprising: The first switch is a first NMOS transistor;
The second switch is a PMOS transistor;
The disconnection detection / reverse connection protection device according to claim 1, wherein the third switch is a second NMOS transistor.   3. The disconnection detection / reverse connection protection device according to claim 2, wherein the second NMOS transistor is formed in a P well by forming a P well with an N well interposed in a P type substrate. The first NMOS transistor has a source connected to the signal line, a gate and a substrate connected to the ground line, a drain connected to the source of the second NMOS transistor,
The PMOS transistor has a source connected to the power line, a gate connected to the ground line, a drain and a substrate connected to an internal power terminal of the circuit,
The source of the second NMOS transistor is connected to the drain of the first NMOS transistor, and the gate, drain and substrate are connected to the power supply line. Disconnection detection / reverse connection protection device.   5. The disconnection detection / reverse operation according to claim 2, wherein the first and second NMOS transistors and the PMOS transistor are formed on the same P-type substrate. Connection protection device. Each circuit comprises a sensor circuit and a control circuit,
6. The control circuit according to claim 1, wherein the control circuit generates a power supply voltage for driving the sensor circuit and processes an output signal from the sensor circuit. 7. Disconnection detection / reverse connection protection device.

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