JP6585827B2 - Sensor device - Google Patents

Description

  The present invention relates to a sensor device to which power is supplied from the outside.

  When the external power supply or ground is disconnected, the sensor output voltage may become unstable. Specifically, a pull-up resistor or a pull-down resistor is connected to the sensor output in order to fix the sensor output when the sensor output is disconnected. The sensor output may become indefinite when the pull-up resistor is connected and the power supply is disconnected, and when the pull-down resistor is connected and the ground line is disconnected.

  When the pull-up resistor is connected and the power source is disconnected, current is supplied from the pull-up resistor to the power source inside the sensor through an element connected to the sensor output. As a current supply path, an ON current of a PMOS transistor for driving a sensor output and a forward current of a parasitic diode between a PMOS substrate and a drain connected to the sensor output can be considered. When a current flows through the internal power supply of the sensor, a current flows through the pull-up resistor, a voltage drop occurs, and the sensor output becomes indefinite depending on the amount of current. In addition, since the sensor internal power supply becomes unstable, there is a possibility that malfunction occurs and the sensor output becomes unstable.

  When the pull-down resistor is connected and the ground line is disconnected, the pull-down resistor is turned on by the on-current of the NMOS transistor for driving the sensor output or the forward current of the parasitic diode between the NMOS substrate and the drain connected to the sensor output. A current flows and the sensor output becomes indefinite.

  For example, there are physical quantity sensor devices described in Patent Documents 1 to 3 as conventional examples for preventing such sensor output from becoming indefinite at the time of disconnection.

  Patent Document 1 does not have a PMOS transistor that flows an on-current from the internal power supply to the sensor output, and the current from the substrate to the internal power supply becomes a reverse current between the substrate of the PMOS transistor connected to the sensor output and the internal power supply. A diode is inserted so that no current flows through the forward current of the parasitic diode between the drain of the PMOS transistor and the substrate. In this way, measures are taken so that no current flows from the sensor output to the internal power supply. Since no current flows from the sensor output into the sensor, the sensor output is fixed near the power supply by the pull-up resistor.

  In Patent Document 2, the sensor output is set near the power supply voltage or near the ground potential depending on the resistance ratio of the pull-up resistor connected between the sensor output and the power supply voltage and the pull-down resistor connected between the sensor output and the ground at the time of disconnection. A fixed circuit is shown in FIG.

  Patent Document 3 discloses a circuit in which a transistor is connected between a power supply and a sensor output, and the sensor output is fixed near the power supply voltage by turning on the transistor when the ground is disconnected.

JP 2014-025731 A JP 2003-304633 A JP 2011-089849 A

  In the above-described conventional techniques, the range of pull-up resistance and pull-down resistance values outside the sensor that can be used is narrow, and the circuits that can be connected are limited.

  That is, in the circuit of Patent Document 1, since the sensor output is driven to the high side by the external pull-up resistor, the pull-up resistor is essential, and the pull-down resistor cannot be selected. In addition, the pull-up resistor needs to be less than a certain resistance value due to restrictions on the operation speed.

  In the circuit of Patent Document 2, the sensor output is fixed by the resistance ratio of the pull-up and pull-down resistors at the time of disconnection. For this reason, in order to fix the sensor output near the power supply voltage or the ground potential, it is necessary to increase the resistance ratio. Considering power consumption, it is necessary to make it more than a certain resistance value.

  In the circuit of Patent Document 3, when the potential difference between the sensor output and the power supply voltage becomes small, the potential difference between the gate and the source of the transistor that supplies current from the power supply voltage to the sensor output becomes small. Is difficult to fix around the power supply voltage. In order to fix near the power supply voltage, it is necessary to increase the resistance value of the external pull-down resistor or increase the size of the transistor. However, considering the increase in cost due to the increase in transistor size, the pull-down resistance value needs to be greater than a certain resistance value.

  An object of the present invention is to realize a sensor device capable of fixing a sensor output near a power supply voltage or near a ground at the time of disconnection.

  In order to solve the above problems, a sensor device of the present invention is, for example, a sensor device that detects a predetermined physical quantity, and includes a power supply terminal and a ground terminal to which power is supplied from the outside, and a sensor output of the sensor device. An output terminal that outputs an output signal to the outside; a signal processing circuit that generates an output signal to the output terminal from a signal from a sensor element that detects a physical quantity; and a control signal that controls a sensor output circuit; and the sensor When the wiring between the device and the external power source or the wiring with the external ground is disconnected, a disconnection detection circuit that detects the disconnection and generates a control signal, the sensor output, the internal power source of the sensor device, and And a cutoff switch for cutting off a current path between the internal grounds.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the sensor apparatus which can fix a sensor output to a power supply or ground vicinity at the time of a disconnection.

Circuit configuration of the first embodiment Operation waveform diagram of the first embodiment Description of disconnection location of the first embodiment Circuit configuration of the second embodiment Operation waveform diagram of the second embodiment Description of disconnection location of the second embodiment Configuration example of disconnection detection circuit of third embodiment Operation waveform diagram of disconnection detection circuit of third embodiment

  Embodiments of the present invention will be described below with reference to the drawings.

  The structure of the first embodiment of the present invention is shown in FIG. First, connection between the sensor device of this embodiment and an external device will be described. The sensor output 4 of the sensor device 1 is input to a sensor output receiving device 2 such as an ECU (Engine Control Unit). The power and ground (GND) of the sensor device 1 are supplied from the sensor output receiving device 2 through the power supply wiring 3 and the GND wiring 5. The power supply wiring 3 and the sensor output 4 are connected by a pull-up resistor 6. In general, the pull-up resistor 6 is disposed inside the input circuit of the sensor output receiving device 2, and when the wiring of the sensor output 4 is disconnected, the disconnection is prevented by fixing the input voltage to the sensor output receiving device 2 to the power supply voltage. Plays the role of detecting.

  Next, the configuration of the sensor device 1 will be described. The sensor device 1 includes a low voltage detection circuit 11, a sensor element 12, a signal processing circuit 13, a disconnection detection circuit 14, a sensor output drive PMOS 15, a sensor output drive NMOS 16, a sensor power supply PMOS 15 substrate feed switch 17, and a sensor output drive NMOS 16. It is composed of a substrate feed switch 18 and a load resistor 10. The diode 19 is a parasitic diode between the P diffusion constituting the drain of the sensor output driving PMOS 15 and the N well constituting the substrate. The diode 20 is a parasitic diode between the N diffusion constituting the drain of the sensor output drive NMOS 16 and the P well constituting the substrate.

  The low voltage detection circuit 11 controls the operation of the signal processing circuit 13 by outputting a specific high or low voltage to the signal 21 when the voltage of the internal power supply 8 is equal to or lower than a certain voltage at which normal operation of the internal circuit is difficult. To do. The sensor element 12 is a sensor element that detects a physical quantity and outputs an electrical signal corresponding to the physical quantity to the sensor element output 22. The signal processing circuit 13 is a circuit block for processing a sensor element control circuit and an output signal of the sensor element, and is an analog circuit such as a clock generation circuit, a constant voltage source generation circuit, a temperature sensor, an ADC, a DAC, and a digital circuit. DSP, MCU, cache, nonvolatile memory, communication I / F, and the like. The signal processing circuit 13 controls the gate signals 26 and 27 of the sensor output driving PMOS 15 and the sensor output driving NMOS 16 so as to output a signal corresponding to the output of the sensor element to the sensor output 4. The sensor output 4 of the first embodiment is a voltage output in which the voltage value of the sensor output 4 changes according to the physical detection value of the sensor. For the feedback control of the operational amplifier included in the main circuit 13, the sensor output 4 is the main output. It is input to the circuit 13. In this embodiment, the sensor output drive PMOS and the sensor output drive NMOS are final stage buffers of the operational amplifier. The disconnection detection circuit 14 detects that the wiring of VDD3 or GND5 is disconnected and the power supply or the GND potential is not supplied to the sensor device 1, and the sensor output driving PMOS 15, NMOS 16, and substrate power supply switches 18, 19 are turned on / off. , The sensor output 4 is fixed to a high or low voltage, and the sensor output receiving device 2 can detect that a disconnection has occurred in the wiring that supplies the power or GND to the sensor device 1.

Next, operation | movement of the sensor apparatus 1 is demonstrated using the waveform diagram of FIG. In the waveform diagram, the horizontal axis represents time and the vertical axis represents the voltage of each signal. While the voltage value of writing specific values for clarity, it is also applicable in other different voltages is not limited to Re this. The case where a disconnection occurs in VDD3 at time T1 is described.

  First, the normal operation before T1 will be described. The operating voltage 5V of the sensor device 1 is supplied from the sensor receiving device 2 to the VDD 3, and the voltage of the VDD 3 is supplied to the internal power supply 8 of the sensor device 1 through wiring connection, and the internal power supply 8 is also 5V. The GND 5 is supplied with the GND potential from the sensor receiving device 2, and the potential of the GND 5 is supplied to the internal GND 9 of the sensor device 1 through wiring connection. Since the internal power supply 8 is the operating voltage of 5 V, low is output as the output signal 21 of the low voltage detection circuit 11.

  Signals corresponding to the output signal of the sensor element 12 are output to the output signals 23 and 24 of the signal processing circuit 13. During normal operation, the disconnection detection circuit 14 connects the signal 23 to the signal 26 and the signal 24 to the signal 27. Thereby, the gate signals of the sensor output drive PMOS 15 and the NMOS 16 are controlled by the output signal of the signal processing circuit 13, and a signal corresponding to the output signal of the sensor element 12 is output to the sensor output 4.

  Further, the disconnection detection circuit 14 sets the output signal 25 to the low state, the output signal 28 to the high state, and turns on the substrate power supply switches 17 and 18. As a result, the voltage of the internal power supply 8 is supplied to the substrate of the PMOS 15, and the voltage of the internal GND 9 is supplied to the substrate of the NMOS 16. By supplying the source voltage to the substrate, the PMOS 15 and the NMOS 16 can operate stably.

  Next, a case where the wiring for supplying the voltage VDD3 to the sensor device 1 is disconnected at time T1 will be described. FIG. 3 shows a disconnection state of the VDD3 wiring.

  As shown in FIG. 3, when the VDD3 wiring is disconnected, no current is directly supplied from VDD3 to the internal power supply 8 in the sensor device 1. On the other hand, a current is supplied from the VDD 3 to the sensor output 4 through the external pull-up resistor 6, and the on-current of the PMOS 15 and the forward current of the parasitic diode 19 are supplied from the sensor output 4 to the internal power supply 8 shown in FIG. Through which current is supplied.

  Although current is supplied from the sensor output 4, the voltage of the internal power supply 8 is lowered by the operating current of the internal circuit due to the on-resistance of the pull-up resistor 6 and the PMOS 15 and the forward voltage of the parasitic diode 19.

  When the internal power supply 8 becomes equal to or lower than the low voltage detection voltage 4V of the low voltage detection circuit 11 at time T2 shown in FIG. 2, the low voltage detection circuit 11 outputs high to the low voltage detection signal 21. When the low voltage detection signal 21 becomes high, the circuits constituting the signal processing circuit 13 stop operating, fixing the signal 23 to high and the signal 24 to low.

  When the signal 23 becomes high, the signal 26 connected to the signal 23 also becomes high, and the PMOS 15 is turned off. When the signal 24 becomes low, the signal 27 connected to the signal 24 also becomes low, and the NMOS 16 is turned off.

  Since the PMOS 15 is turned off, only the forward current of the parasitic diode 19 supplies current from the sensor output 4 to the internal power supply 8, and the internal power supply 8 receives the forward voltage ( The voltage is generally lower by about 0.7V). The voltage of the sensor output 4 is determined by the ratio between the internal impedance of the sensor device 1 and the resistance value of the external pull-up resistor 6. The internal impedance of the sensor device 1 is determined by the DC current and leak current of the signal processing circuit 13 and the resistance value of the load resistor 10 because the signal processing circuit 13 is stopped and no operating current flows.

  The disconnection detection circuit 14 outputs the voltage of the sensor output 4 to the signal 25 and the signal 26 when the voltage of the internal power supply 8 becomes lower than the voltage of the sensor output 4 by a certain voltage or more. Since the voltage of the internal power supply 8 is lower than the voltage of the sensor output 4, the source of the PMOS 15 becomes a terminal connected to the sensor output 4, and the source of the PMOS 15 is at the same potential and is turned off.

  Further, since current is supplied to the internal power supply 8 through the substrate of the PMOS 15, the voltage of the substrate of the PMOS 15 is higher than the voltage of the internal power supply 8, and the substrate feed switch 17 has a terminal connected to the substrate of the PMOS 15 as a source. Since the gate voltage becomes higher than the source voltage, the transistor is turned off.

  Since both the PMOS 15 and the substrate feed switch 17 are turned off, no current is supplied from the sensor output 4 to the internal power supply 8, and the internal power supply 8 is reduced to 0 V due to the internal impedance of the sensor device 1. The internal signals of the sensor device 1 excluding the output signal of the disconnection detection circuit 14 are reduced to 0V as the internal power supply 8 is reduced. Further, since the internal power supply is reduced to 0V, the gate signals of the NMOSs 16 and 18 are also set to 0V, and there is no current path from the sensor output to the GND through the sensor device 1, so that the sensor output 4 is set to 5V by the pull-up resistor 6. Fixed.

  With the above-described configuration, the external device can detect the disconnection without the sensor output becoming indefinite when the VDD3 is disconnected. In general, since the DC current and leakage current of the signal processing circuit 13 are very small, even if the external pull-up resistor 6 is increased, the voltage of the sensor output 4 can be fixed around 5V.

  In order for the circuit to operate as described above, the internal power supply 8 needs to be equal to or lower than the low voltage detection voltage, and the voltage of the internal power supply 8 reduced by the impedance of the current supply path from the sensor output 4 and the operating current is It is necessary to set the resistance value of the external pull-up resistor 6 and the low voltage detection voltage so as to be lower than the low voltage detection voltage. The resistance value of the load resistor 10 needs to be set so that the voltage difference generated between the sensor output 4 and the internal power supply 8 is equal to or higher than the detection voltage of the disconnection detection circuit 14. The voltage difference between the sensor output 4 and the internal power supply 8 is determined by the relationship between the forward voltage of the parasitic diode 19 and the current.

  When an external pull-up resistor is connected to sensor output 4 and GND5 is disconnected, there is no current path from sensor output to GND5, so all nodes of the sensor device are fixed at 5V, and sensor output 4 is set to 5V. Fixed.

  A second embodiment of the present invention is shown in FIG. The difference from FIG. 1 is that an external pull-down resistor 7 is connected to the sensor output 4 instead of the external pull-up resistor 6. In addition, about the structure similar to Example 1, the same code | symbol is used and description is abbreviate | omitted.

  The operation of the sensor device 1 when the external pull-down resistor 7 is connected to the sensor output 4 and the wiring of the GND 5 is disconnected will be described with reference to the waveform diagram of FIG. In addition, the disconnection location of GND5 is shown in FIG.

  A case where a disconnection occurs at time T3 will be described. The normal operation is performed until time T3, which is the same as the normal operation before time T1 in the first embodiment. Therefore, here, the operation after time T3 when the disconnection of the GND 5 occurs will be described.

  When the GND 5 is disconnected as shown in FIG. 6, the 0V voltage is not directly supplied to the internal GND 9 of the sensor device 1 shown in FIG. On the other hand, a current is extracted from the GND 5 to the sensor output 4 through the external pull-down resistor 7, and a current is extracted from the internal GND 9 to the sensor output 4 through the on-current of the PMOS 16 and the forward current of the parasitic diode 20. Although current is drawn from the sensor output 4, the voltage of the internal GND 5 rises due to the operating current of the internal circuit because of the on-resistance of the pull-down resistor 7 and the NMOS 16 and the forward voltage of the parasitic diode.

  When the voltage difference between the internal ground 9 and the internal power supply 8 becomes equal to or lower than the low voltage detection voltage 4V of the low voltage detection circuit 11 at time T4 shown in FIG. 5, the low voltage detection circuit 11 outputs high to the low voltage detection signal 21 To do. When the low voltage detection signal 21 becomes high, the circuits constituting the signal processing circuit 13 stop operating, fixing the signal 23 to high and the signal 24 to low.

  When the signal 23 becomes high, the signal 26 connected to the signal 23 also becomes high, and the PMOS 15 is turned off. When the signal 24 becomes low, the signal 27 connected to the signal 24 also becomes low, and the NMOS 16 is turned off.

  When the NMOS 16 is turned off, only the forward current of the parasitic diode 20 draws current from the internal GND 9 to the sensor output 4, and the internal GND 9 The voltage becomes higher by about 0.7V. The voltage of the sensor output 4 is determined by the ratio between the internal impedance of the sensor device 1 and the resistance value of the external pull-down resistor 7. The internal impedance of the sensor device 1 is determined by the DC current and leak current of the signal processing circuit 13 and the resistance value of the load resistor 10 because the signal processing circuit 13 is stopped and no operating current flows.

  The disconnection detection circuit 14 outputs the voltage of the sensor output 4 to the signal 27 and the signal 28 when the voltage of the internal GND 9 becomes higher than the voltage of the sensor output 4 by a certain voltage or more. Since the voltage of the internal GND 9 is higher than the voltage of the sensor output 4, the source of the NMOS 16 becomes a terminal connected to the sensor output 4, and the NMOS 16 is turned off with the source and gate having the same potential. Further, since current is drawn from the internal GND 9 through the substrate of the NMOS 16, the voltage of the substrate of the NMOS 16 is lower than the voltage of the internal GND 9, and the substrate feed switch 18 has the source connected to the terminal connected to the substrate of the NMOS 16, and the gate voltage Becomes higher than the source voltage, so that it is turned off. When both the NMOS 16 and the substrate power supply switch 18 are turned off, current cannot be drawn from the internal GND 9 to the sensor output 4, and the internal GND 9 rises to the voltage 5 V of the internal power supply 8 due to the internal impedance of the sensor device 1. The internal signal of the sensor device 1 excluding the output signal of the disconnection detection circuit 14 rises to 5V as the internal GND 9 rises. Since all the internal nodes of the sensor device 1 rise to 5V, the gate voltages of the PMOSs 15 and 17 are also 5V and are turned off, so that no current is drawn from the sensor device 1 to the sensor output 4, and the sensor output 4 is pulled down. It is fixed at 0V by the resistor 7.

  With the above-described configuration, the external device can detect the disconnection without the sensor output becoming indefinite when the GND 5 is disconnected. In general, since the DC current and leakage current of the signal processing circuit 13 are very small, even if the external pull-down resistor 7 is increased, the voltage of the sensor output 4 can be fixed near 0V.

  In the third embodiment of the present invention, a configuration example of the disconnection detection circuit 14 is shown in FIG. In this embodiment, the disconnection detection circuit 14 includes a resistor 41, an NMOS 42, a PMOS 44, a resistor 46, a PMOS 47, a resistor 49, a resistor 50, an NMOS 51, a PMOS 53, an NMOS 54, a PMOS 55, an NMOS 56, a PMOS 57, an NMOS 58, a PMOS 59, an NMOS 60, and a parasitic diode 43 of each MOS. , 45, 48, 52. The PMOS 59 is a substrate feed switch that connects each PMOS substrate constituting the disconnection detection circuit 14 and the internal power supply 8. The NMOS 60 is a substrate feed switch that connects each NMOS substrate constituting the disconnection detection circuit 14 to the internal GND 9.

  The resistor 41, the NMOS 42, the PMOS 44, and the resistor 46 constitute a circuit that generates a control signal when the voltage of the sensor output 4 becomes lower than the voltage of the internal GND 9. The PMOS 47, the resistor 49, the resistor 50, and the NMOS 51 constitute a circuit that generates a control signal when the voltage of the sensor output 4 becomes higher than the voltage of the internal power supply 8. The PMOS 53 and the NMOS 54 constitute a switch between the signal 23 and the signal 26, and the PMOS 55 and the NMOS 56 form a switch between the signal 24 and the signal 27.

  The PMOS 57 fixes the signal 26 to the voltage of the sensor output signal 4 when the disconnection of the VDD 3 is detected, and the NMOS 58 fixes the signal 27 to the voltage of the sensor output signal 4 when the disconnection of the GND 5 is detected.

  First, the circuit operation when the external pull-up resistor shown in FIG. 3 is connected and VDD3 is disconnected will be described. FIG. 8 shows a waveform diagram. The internal power supply 8, the internal GND 9, and the sensor output 4 are the same as the waveforms shown in FIG. First, a description will be given of the normal operation before the disconnection of the VDD3 wiring occurs at time T1.

  The PMOS 47 has a gate connected to the internal power supply 8 and a source connected to the sensor output 4. During normal operation, the voltage of the sensor output 4 does not become higher than the voltage of the internal power supply 8, so that the PMOS 47 is turned off. Since the PMOS 47 is in the off state, the signal 25 becomes the same voltage 0V as the internal GND by the resistor 49. Since the signal 25 is 0V, the NMOS 51 connected to the gate of the signal 25 is also turned off, and the signal 63 becomes the same voltage 5V as the internal power supply by the resistor 50. Since the signal 25 is 0V, the PMOS 53 is turned on. Further, since the signal 63 is 5V, the NMOS 54 is also turned on, and the PMOS 57 is turned off. Since the PMOS 53 and the NMOS 54 are on and the PMOS 57 is off, the voltage value of the signal 23 is output as the signal 26. Since the signal 25 is 0V, the PMOS 59 is turned on, and the voltage 5V of the internal power supply 8 is supplied to each PMOS substrate. The NMOS 42 has a gate connected to the internal GND and a source connected to the sensor output 4. During normal operation, the voltage of the sensor output 4 never becomes lower than the voltage of the internal GND 9, so that the NMOS 42 is turned off. Since the NMOS 42 is in the off state, the signal 28 becomes the voltage 5V of the internal power supply 8 by the resistor 41. Since the signal 28 is 5V, the PMOS 44 connected to the gate of the signal 28 is also turned off, and the signal 64 is drawn by the resistor 46 and becomes the voltage 0V of the internal GND 9. Since the signal 28 is 5V, the NMOS 56 is turned on. Further, since the signal 64 is 0V, the PMOS 55 is also turned on, and the NMOS 58 is turned off. Since the PMOS 55 and the NMOS 56 are on and the NMOS 58 is off, the voltage value of the signal 24 is output as the signal 27. Further, since the signal 28 is 5V, the NMOS 60 is turned on, and the voltage of 0V of the internal GND 9 is supplied to each NMOS substrate.

  Next, an operation after the disconnection of the VDD3 wiring at time T1 will be described. As described in the first embodiment, the voltage of the internal power supply 8 decreases, and the voltage of the internal power supply 8 becomes lower than the voltage of the sensor output 4 by the forward voltage of the parasitic diode 19. When the voltage of the internal power supply 8 falls below the threshold voltage of the PMOS 47 with respect to the voltage of the sensor output 4, the PMOS 47 is turned on. If the PMOS 47 is turned on and the resistance value of the resistor 49 is designed to be sufficiently higher than the on-resistance of the PMOS 47, the signal 25 becomes the voltage of the sensor output 4. The signal 25 becomes the voltage of the sensor output 4, and the NMOS 51 is also turned on. If the resistance value of the resistor 50 is designed to be sufficiently higher than the ON resistance of the NMOS 51, the signal 63 becomes the voltage 0V of the internal GND9. Since current is supplied from the sensor output 4 to the sensor device 1, the voltages at the internal nodes 23 and 26 of the sensor device 1 are lower than the voltage at the sensor output 4. Since the signal 25 becomes the voltage of the sensor output 4, the gate voltage of the PMOS 53 becomes higher than the signals 23 and 26, and the PMOS 53 is turned off. Since the signal 63 becomes 0V, the NMOS 54 is turned off and the PMOS 57 is turned on. Since the PMOS 53 and the NMOS 54 are turned off, the signal 26 is disconnected from the signal 23 and the voltage of the sensor output 4 is supplied by the PMOS 57. Since the signal 25 becomes the potential of the sensor output 4, the PMOS 59 is turned off, and current is prevented from being supplied to the internal power supply 8 due to the forward current of the PMOS parasitic diode connecting the sensor output 4 and the internal power supply 8. . When the wiring of VDD3 is disconnected, the sensor output 4 does not become lower than the internal GND 9, so that the voltage of the internal power supply 8 is output as the signal 28 and the voltage 0V of the internal GND is output as the signal 64. . Since the signal 25 and the signal 26 become the voltage of the sensor output 4, the PMOS 15 and the PMOS 17 in FIG. 1 are turned off, and there is no current path from the sensor output 4 to the GND through the sensor device 1. 4 is fixed to a voltage 5V of VDD3.

  Next, the circuit operation when the external pull-down resistor shown in FIG. 6 is connected and the GND 5 is disconnected will be described. FIG. 9 shows a waveform diagram. The internal power supply 8, the internal GND 9, and the sensor output 4 are the same as the waveforms shown in FIG. The normal operation before the disconnection of the GND5 wiring at time T2 is the same as the normal operation already described when the VDD3 is disconnected. An operation after GND 5 is disconnected at time T2 will be described. As described in the second embodiment, the voltage of the internal GND 9 rises, and the voltage of the internal GND 9 becomes higher than the voltage of the sensor output 4 by the forward voltage of the parasitic diode 20. When the voltage of the internal GND 9 rises above the threshold voltage of the NMOS 42 with respect to the voltage of the sensor output 4, the NMOS 42 is turned on. If the resistance value of the resistor 41 is designed to be sufficiently higher than the on-resistance of the NMOS 42, the signal 28 becomes the voltage of the sensor output 4 when the NMOS 42 is turned on. The signal 28 becomes the voltage of the sensor output 4, and the PMOS 44 is also turned on. If the resistance value of the resistor 46 is designed to be sufficiently higher than the on-resistance of the PMOS 44, the signal 64 becomes the voltage 5V of the internal power supply 8V. Since the sensor device 1 has a current drawn from the sensor output 4, the voltages of the internal nodes 24 and 27 of the sensor device 1 are higher than the voltage of the sensor output 4. Since the signal 28 becomes the voltage of the sensor output 4, the gate voltage of the NMOS 56 is lower than the signals 24 and 27, and the NMOS 56 is turned off. Since the signal 64 becomes 5V, the PMOS 55 is turned off and the NMOS 58 is turned on. Since the NMOS 56 and the PMOS 55 are turned off, the signal 27 is disconnected from the signal 24 and is extracted to the voltage of the sensor output 4 by the NMOS 58. Since the signal 28 becomes the potential of the sensor output 4, the NMOS 60 is turned off to prevent the current from being drawn from the internal GND 9 to the sensor output 4 due to the forward current of the NMOS parasitic diode connecting the sensor output 4 and the internal GND 9. To do. When the wiring of the GND 5 is disconnected, the voltage of the sensor output 4 does not become higher than that of the internal power supply 8, so the voltage of the internal GND 9 is output as the signal 25 and the voltage 5V of the internal power supply is output as the signal 63. Is done. Since the signal 27 and the signal 28 become the voltage of the sensor output 4, the NMOS 16 and the NMOS 18 in FIG. 4 are turned off, and there is no current path from the sensor output 4 to the power supply through the sensor device 1. Is fixed to the voltage 0V of GND5.

  As described above, the circuit configuration of the disconnection detection circuit 14 shown in the present embodiment detects the disconnection of the power supply or the GND by comparing the voltage of the sensor output with the voltage of the internal power supply and the internal GND. Control is performed so that the transistor between the sensor output and the internal power supply or the internal GND is turned off so that a current path does not occur from the output to the internal power supply or the internal GND through the sensor device. Further, since the disconnection detection circuit operates using the voltage of the sensor output, it can operate normally even when all the internal nodes of the sensor device 1 become GND or the power supply voltage. However, since the IR drop occurs in the sensor output voltage when the current consumption of the disconnection detection circuit flows to the external pull-up resistor or pull-down resistor, the resistance values of the external pull-up resistor and pull-down resistor are the power consumption of the disconnection detection circuit. It is necessary to determine the upper limit in consideration of the voltage range defined as disconnection detection.

DESCRIPTION OF SYMBOLS 1 ... Sensor apparatus, 3 ... VDD (power supply terminal), 4 ... Sensor output, 5 ... GND (ground terminal), 6 ... Pull-up resistor, 7 ... Pull-down resistor, 13 ... Signal processing circuit, 14 ... Disconnection detection circuit, 15 ... PMOS transistor for output driver, 16 ... NMOS transistor for output driver, 17 ... PMOS transistor for substrate feed switch, 18 ... NMOS transistor for substrate feed switch

Claims (10)

A sensor device for detecting a predetermined physical quantity,
A power supply terminal and a ground terminal supplied with power from outside;
An output terminal for outputting an output signal of the sensor output of the sensor device to the outside;
A signal processing circuit that generates an output signal to the output terminal from a signal from a sensor element that detects a physical quantity, and generates a control signal that controls the sensor output circuit;
When the wiring between the sensor device and the external power source or the wiring with the external ground is disconnected, a disconnection detection circuit that detects a disconnection and generates a control signal;
A cut-off switch for cutting off a current path between the sensor output and the internal power supply and internal ground of the sensor device;
A sensor device comprising a pull-up resistor connected between the sensor output and an external power supply outside the sensor device, or a pull-down resistor connected between the sensor output and an external ground . A sensor device for detecting a predetermined physical quantity,
A power supply terminal and a ground terminal supplied with power from outside;
An output terminal for outputting an output signal of the sensor output of the sensor device to the outside;
A signal processing circuit that generates an output signal to the output terminal from a signal from a sensor element that detects a physical quantity, and generates a control signal that controls the sensor output circuit;
When the wiring between the sensor device and the external power source or the wiring with the external ground is disconnected, a disconnection detection circuit that detects a disconnection and generates a control signal;
A cut-off switch for cutting off a current path between the sensor output and the internal power supply and internal ground of the sensor device;
Detects that the voltage falls below a specified value there is an internal power supply of the sensor device, possess a low voltage detection circuit for generating a signal, a,
The signal processing circuit receives the output signal of the low voltage detection circuit, and fixes the control signal of the sensor output circuit to high or low when the power supply voltage becomes a certain voltage or less. . A sensor device for detecting a predetermined physical quantity,
A power supply terminal and a ground terminal supplied with power from outside;
An output terminal for outputting an output signal of the sensor output of the sensor device to the outside;
A signal processing circuit that generates an output signal to the output terminal from a signal from a sensor element that detects a physical quantity, and generates a control signal that controls the sensor output circuit;
When the wiring between the sensor device and the external power source or the wiring with the external ground is disconnected, a disconnection detection circuit that detects a disconnection and generates a control signal;
Have a, a cutoff switch to cut off the current path between the internal power supply and the internal ground of the sensor device and the sensor output,
The sensor output circuit is composed of PMOS and NMOS,
A current cutoff switch between the PMOS substrate node and the internal power supply;
A current cutoff switch between the NMOS substrate node and the internal ground;
Off switch for the current interruption, the sensor device according to claim Rukoto is controlled by a control signal of the disconnection detecting circuit. A sensor device for detecting a predetermined physical quantity,
A power supply terminal and a ground terminal supplied with power from outside;
An output terminal for outputting an output signal of the sensor output of the sensor device to the outside;
A signal processing circuit that generates an output signal to the output terminal from a signal from a sensor element that detects a physical quantity, and generates a control signal that controls the sensor output circuit;
When the wiring between the sensor device and the external power source or the wiring with the external ground is disconnected, it is detected that the power source or the ground potential is not supplied to the sensor device, and the sensor output a disconnection detecting circuit for generating a control signal of the circuit,
A sensor device comprising: a shut-off switch that shuts off a current path between the sensor output and an internal power source and an internal ground of the sensor device. The sensor device according to claim 4,
The disconnection detection circuit fixes the sensor output to a high or low voltage by generating a control signal of the sensor output circuit. The sensor device according to claim 4 ,
A sensor device comprising a pull-up resistor connected between the sensor output and an external power source outside the sensor device, or a pull-down resistor connected between the sensor output and an external ground. The sensor device according to any one of claims 1 to 4 ,
The disconnection detection circuit compares the voltage of the sensor output with the voltage of the power supply inside the sensor device,
When the voltage of the sensor output is higher than a voltage of a power source inside the sensor device by a certain value or more, the cutoff switch and the sensor output circuit are configured to cut off a current path between the sensor output and the internal power source of the sensor device. A sensor device for controlling an input signal of the sensor. The sensor device according to any one of claims 1 to 4 ,
The disconnection detection circuit compares the voltage of the sensor output with the voltage of the ground inside the sensor device,
When the voltage of the sensor output is lower than the ground voltage inside the sensor device by a certain value or more, it is determined that the wiring connecting the sensor device and the external ground is disconnected,
Sensor device and controls the input signal of the cutoff switch and the sensor output circuit so as to cut off the current path between the internal ground of the sensor device and the sensor output. The sensor device according to claim 4 ,
Detecting that the internal power supply of the sensor device is below a certain voltage, and having a low voltage detection circuit for generating a signal;
It said signal processing circuit is output signal input of said low-voltage detection circuit, a sensor device which becomes below a predetermined voltage is the supply voltage, characterized in that to fix the control signal of the sensor output circuit to the high or wax . The sensor device according to claim 4 ,
The sensor output circuit is constituted by PMOS and N MOS,
A current cutoff switch between the PMOS substrate node and the internal power supply;
A current cutoff switch between the NMOS substrate node and the internal ground;
ON / OFF of the current interruption switch is controlled by a control signal of the disconnection detection circuit.

Images