JP2011089849A - Wire breaking detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wire breaking detector for actualizing a wire breaking detecting function, without forming an oxide film insulation isolation structure on an SOI (silicon-on-insulator) substrate and attaining reduction in the manufacturing cost, at attainment. <P>SOLUTION: According to the wire breaking detector, wire break in a ground line 50 is detected among a power supply line 30, the ground line 50 and a signal line 40 which connect a sensor circuit 10A and a control circuit 20. As a result, the detector includes a pull-down resistor R101 provided between the signal line 40 and the ground line 50, and a wire breaking detection circuit 102A for making 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. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a disconnection detection device that detects disconnection of a path for supplying power supply voltage, signals, and the like to various circuits.

FIG. 5 is a block diagram showing an example of the configuration of a conventional sensor device to which this type of disconnection detection device is applied.
As shown in FIG. 5, 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. 6 is a circuit diagram of an amplification processing unit which is a part of the functional circuit 102 of FIG. 5 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. 5, when the external ground line 50 is disconnected in a state where the pull-down resistor R201 is connected between the input terminal Vin of the control circuit 20 and the ground terminal GND, a current flows 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.

JP 2004-301670 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a disconnection detection device that can realize a disconnection function without forming an oxide film insulating isolation structure on an SOI substrate and can reduce the manufacturing cost in realizing the disconnection function. .

In order to solve the above-described problems and achieve the object of the present invention, each invention has the following configuration.
1st invention is a disconnection detection apparatus which detects the disconnection of the said ground line among the power supply line which connects a 1st circuit and a 2nd circuit, a ground line, and a signal line, Comprising: A pull-down resistor provided between the ground lines; and a disconnection detection circuit that increases the potential of the signal line in the vicinity of the power supply potential of the power supply line in conjunction with the pull-down resistor when the ground line is disconnected.

In a second aspect based on the first aspect, the disconnection detection circuit raises the potential of the signal line to near the power supply potential of the power supply line, and fixes or maintains the state.
In a third aspect based on the second aspect, the disconnection detection circuit comprises an N-type MOS transistor.
In a fourth aspect based on the third aspect, the MOS 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 power line.
According to a fifth invention, in the first to fourth inventions, the first circuit includes a sensor circuit, and the second circuit generates a power supply voltage for driving the sensor circuit, and from the sensor circuit, It consists of a control circuit that processes the output signal.

According to the present invention having such a configuration, when the ground line is disconnected in a state where the power supply line and the ground line are normally connected, the potential of the signal line is raised to the vicinity of the power supply potential of the power supply line. Can be fixed or maintained in condition.
In addition, when the power supply line or the signal line is disconnected in a state where the power supply line and the ground line are normally connected, the potential of the signal line can be changed to the vicinity of the potential of the ground line and fixed or maintained in that state.
For this reason, according to the present invention, the disconnection function can be realized without forming an oxide film insulating isolation structure on the SOI substrate, and therefore, the manufacturing cost can be suppressed in realizing the disconnection function.

It is a block diagram which shows the structure of the sensor apparatus to which 1st Embodiment of the disconnection detection apparatus of this invention is applied. It is sectional drawing which shows the cross-section of the MOS transistor applied to a disconnection detection circuit. It is a block diagram which shows the structure of the sensor apparatus to which 2nd Embodiment of the disconnection detection apparatus of this invention is applied. It is sectional drawing which shows the cross-section of the bipolar transistor applied to a disconnection detection circuit. 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 the first embodiment of the disconnection detection 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.

In the sensor device, the sensor circuit 10A and the control circuit 20 are connected to each other via a power line 30, a signal line (output line) 40, and a ground line 50, and the power line 30, the signal line 40, and the ground line are connected. When any one of 50 is disconnected, the disconnection is detected.
As shown in FIG. 1, the sensor circuit 10A includes a sensor 101, a functional circuit 102A, a disconnection detection circuit 103, a power supply terminal Vcc, an output terminal Vout, and a ground terminal GND.

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.
The sensor 101 and the functional circuit 102A are connected to the power supply terminal Vcc and the ground terminal GND, respectively, and are driven by the power supply voltage supplied from the control circuit 20 through the power supply line 30. 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.

  The disconnection detection circuit 103 is linked to the pull-down resistor R101 when the ground line 50 is disconnected, and the output potential of the output terminal Vout (the potential of the signal line 40) of the sensor circuit 10A is the potential of the power supply terminal Vcc (power supply line 30). Raise to near and fix or maintain that state. In other words, the disconnection detection circuit 103 links with the pull-down resistor R101 when the ground line 50 is disconnected, and changes the potential of the input terminal Vin of the control circuit 20 to near the potential of the power supply voltage Vcc, and the state after the change To fix or maintain.

  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 power supply terminal Vcc, 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.

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 an N-type MOS transistor Tr101 used in the disconnection detection circuit 103.
As shown in FIG. 2, the N-type MOS transistor Tr <b> 101 is configured using a silicon P-type substrate 60. That is, a P well 61 is formed in a P-type substrate 60, and an N + region 62 serving as a source region and an N + region 63 serving as a drain region are formed in the P well 61. A gate 64 is formed on the P well 61 via an insulator.

Further, the N + region 62 serving as the source region is connected to the output terminal Vout, the N + region 63 serving as the drain region is connected to the power supply terminal Vcc, and the gate 64 is connected to the ground terminal GND. The P-type substrate 60 and the P well 61 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 61 (P-type substrate 60) as an anode and the N + region 62 serving as a source region as a cathode. The parasitic diode D102 uses the P well 61 as an anode and the N + region 63 serving as a drain region as a cathode.

Next, an operation example of the first embodiment configured as described above will be described with reference to FIG.
When the power supply line 30 and the ground line 50 are not disconnected and the power supply voltage generated by the power supply circuit 201 of the control circuit 20 is supplied to the power supply terminal Vcc of the sensor circuit 10A and operates normally, the disconnection detection circuit 103 is configured. The gate voltage of the MOS transistor Tr101 is relatively low with respect to the source voltage. Therefore, the MOS transistor Tr101 is turned off, and no current flows through the MOS transistor Tr101. Therefore, no current flows from the power supply terminal Vcc to the output terminal Vout by the MOS transistor Tr101.

An operation when the ground line 50 is disconnected in this voltage state will be described.
As shown in FIG. 1, 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 51 in the sensor circuit 10A via the sensor 101 and the functional circuit 102A, and the potential of the ground line 51 rises.

  For this reason, since the gate voltage of the MOS transistor Tr101 becomes relatively high with reference to the source voltage, the MOS transistor Tr101 is turned on. As a result, a current flows from the power supply terminal Vcc to the output terminal Vout via the MOS transistor 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 biased in the forward direction, so that no current flows from the output terminal Vout to the ground line 51 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 51 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 function circuit 102A, and the MOS transistor Tr101 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.

(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 disconnection detection circuit 103 in FIG. 1 with a disconnection detection circuit 103A in FIG. For this reason, the same code | symbol is attached | subjected to the same component and the description is abbreviate | omitted.
Similarly to the disconnection detection circuit 103, the disconnection detection circuit 103A is linked to the pull-down resistor R101 when the ground line 50 is disconnected, and supplies the output potential of the output terminal Vout of the sensor circuit 10A (the potential of the signal line 40) to the power supply terminal. The voltage is raised to the vicinity of the potential of Vcc (power supply line 30) and fixed or maintained in that state.

  Therefore, as shown in FIG. 3, the disconnection detection circuit 103A includes an NPN-type bipolar transistor Tr102 that functions as a switch element. The transistor Tr102 has a collector connected to the power supply terminal Vcc, an emitter connected to the output terminal Vout, and a base connected to the ground terminal GND. The transistor Tr102 includes a parasitic diode D103 as shown in FIGS.

FIG. 4 is a cross-sectional view showing a cross-sectional structure of an NPN transistor Tr102 used in the disconnection detection circuit 103A.
The transistor Tr102 is configured using a silicon P-type substrate 70 as shown in FIG. That is, an N-type collector region 74 that is surrounded by P-type isolation layers 71 and 72 and an N-type buried layer 73 and serves as a collector region is formed in the P-type substrate 70. In the N-type collector region 74, a P-type base region 75 serving as a base region is formed. Further, an N-type emitter region 76 that becomes an emitter region is formed in the P-type base region 75.

The N-type collector region 74 is connected to the power supply terminal Vcc, the N-type emitter region 76 is connected to the output terminal Vout, and the P-type base region 75 is connected to the ground terminal GND.
In the transistor Tr102 having such a configuration, a parasitic diode D103 as shown in FIG. 4 is formed. That is, the parasitic diode D103 has the P-type substrate 70 as an anode and the N-type collector region 74 as a cathode.

Next, an operation example of the second embodiment configured as described above will be described with reference to FIG.
As shown in FIG. 3, a case where the ground line 50 is disconnected in a state where the pull-down resistor R101 is connected between the input terminal Vin of the control circuit 20 and the ground terminal GND will be described.
In this case, a current flows from the power supply terminal Vcc to the ground line 51 in the sensor circuit 10A via the sensor 101 and the functional circuit 102A, and the potential of the ground line 51 rises.
For this reason, the base voltage of the transistor Tr102 is relatively high with respect to the emitter voltage, so that the transistor Tr102 is turned on. As a result, a current flows from the power supply terminal Vcc to the output terminal Vout via the MOS transistor 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.

  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. 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 the presence or absence of the disconnection of the ground line 50 by monitoring (detecting) 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 51 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 disconnection detection device of the present invention is configured by connecting a first circuit such as a sensor circuit and a second circuit such as a control circuit with a power supply line, a ground line, and a signal line. It can be applied to various devices and systems connected to each other.

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 R101 ... pull-down resistor

Claims (5)

A disconnection detection device for detecting disconnection of the ground line among a power line, a ground line, and a signal line connecting the first circuit and the second circuit,
A pull-down resistor provided between the signal line and the ground line;
A disconnection detection circuit that increases the potential of the signal line in the vicinity of the power supply potential of the power supply line in conjunction with the pull-down resistor when the ground line is disconnected;
A disconnection detecting device comprising:   The disconnection detection device according to claim 1, wherein the disconnection detection circuit raises the potential of the signal line to near the power supply potential of the power supply line and fixes or maintains the state.   The disconnection detection device according to claim 1, wherein the disconnection detection circuit includes an N-type MOS transistor.   4. The disconnection detecting device according to claim 3, wherein the MOS 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 power supply line. The first circuit comprises a sensor circuit;
5. The circuit according to claim 1, wherein the second circuit includes a control circuit that generates a power supply voltage for driving the sensor circuit and processes an output signal from the sensor circuit. The disconnection detection apparatus according to claim 1.

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