JP5640718B2 - Semiconductor integrated circuit - Google Patents

Description

  The present invention relates to a semiconductor integrated circuit, and more particularly to a technique for detecting an open abnormality of an input terminal of a semiconductor integrated circuit.

  In general, a semiconductor integrated circuit (hereinafter, also referred to as an IC) is mounted on a printed circuit board that constitutes an electronic device, and each terminal of the IC is connected to a connection terminal in a predetermined form on the printed circuit board. Are connected to each wiring formed in A desired signal is input to a signal input terminal of the IC from a signal wiring formed on the printed board.

  For this reason, for example, when the contact between the input terminal of the IC and the connection terminal of the printed circuit board becomes defective and the input terminal of the IC is not connected to the signal wiring of the printed circuit board, the desired signal is normally transmitted to the IC. As a result, the IC function is not realized normally.

  Therefore, as a method of determining whether the connection state between the input terminal of the IC and the signal wiring of the printed circuit board is normal or abnormal, by adding a pull-up resistor or pull-down resistor to the input terminal inside the IC, It is considered that the presence or absence of abnormality is determined by making the voltage of the input terminal different from the normal input voltage and monitoring the voltage of the input terminal (for example, Patent Document 1). reference).

  However, the above technique adds a pull-up resistor or a pull-down resistor that is not necessary for the original function of the IC to the input terminal, and therefore changes the electrical characteristics (input characteristics) at the time of signal input to the input terminal. Become. For this reason, for example, when the input terminal is a terminal for inputting an analog sensor signal and performing AD conversion, the voltage value of the AD conversion target signal changes due to the presence of a pull-up resistor or a pull-down resistor. The detection accuracy of the sensor signal will deteriorate. In addition, the configuration and electrical characteristics of the signal output means provided outside the IC and supplying a signal to the input terminal of the IC must be determined in consideration of the pull-up resistor and the pull-down resistor. It becomes a poor IC.

  Therefore, as a technique for solving the above-mentioned drawbacks, a switch for switching the validity / invalidity of the resistor is further added between the input terminal and the resistor (pull-up resistor or pull-down resistor) inside the IC. There is also a method of turning on the switch only when necessary (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 08-23074 JP 2007-147363 A

However, the above-described method in which a switch is provided between the input terminal and the resistor increases the number of IC components, leading to an increase in IC semiconductor chip size and cost.
The present invention has been made in view of these problems, and an object of the present invention is to make it possible to detect an open abnormality of an input terminal in a semiconductor integrated circuit while suppressing an additional amount of elements and without affecting input characteristics. It is said.

A semiconductor integrated circuit according to a first aspect of the present invention has an input terminal that is connected to a signal wiring formed on a printed board on which the semiconductor integrated circuit is mounted and inputs a signal from the signal wiring.
Further, in this semiconductor integrated circuit, a protection transistor in which a parasitic diode between two output terminals functions as a clamp diode for surge voltage protection is connected between the input terminal and a constant voltage line. In other words, the two output terminals of the protection transistor are connected between the input terminal and the constant voltage line so that the parasitic diode between the output terminals functions as a clamp diode for surge voltage protection. ing.

  If the constant voltage is the power supply voltage of the semiconductor integrated circuit, the protection transistor is provided such that the anode of the parasitic diode is on the input terminal side and the cathode is on the power supply voltage line side. If the constant voltage is a reference ground voltage (= 0 V) lower than the power supply voltage, the protection transistor has a parasitic diode anode on the ground voltage line side and a cathode on the input terminal side. It is provided as follows. In the case of a semiconductor integrated circuit, such a protection transistor is normally provided to protect the input terminal and an internal circuit connected to the input terminal from a surge voltage.

Therefore, in the semiconductor integrated circuit of the first invention , the voltage at the input terminal is different between when the input terminal is normally connected to the signal wiring and when the input terminal is not connected to the signal wiring at an abnormal time. In addition, the driving means drives the protection transistor. Then, the determination unit determines whether there is an open abnormality based on the voltage at the input terminal when the protection transistor is driven by the driving unit.

  In other words, in this semiconductor integrated circuit, the presence or absence of an open abnormality is determined by causing a protective transistor indispensable for protecting a surge voltage at an input terminal to function as a resistor (pull-up resistor or pull-down resistor). When it is not determined whether or not there is an open abnormality, the protection transistor is kept off, so that a pull-up resistor or a pull-down resistor that is not originally required can be connected to the input terminal.

  Therefore, according to this semiconductor integrated circuit, it is possible to detect an open abnormality of the input terminal while suppressing an additional amount of elements and without affecting the input characteristics. This is because the protection transistor is used as both a resistor and a switch in the above-described conventional technology, and it is not necessary to add such a resistor and a switch.

The drive means can constitute a protection transistor (in other words, is turned completely instead of being turned on in the active region) to drive the half-on state so.

That is, when the drive means does not drive the protection transistor and the normal input terminal voltage (ie, the original input voltage) where no open abnormality has occurred is referred to as a normal input voltage, If the transistor is driven to a half-on state, it is a voltage that has a specific correlation with the normal input voltage in a normal state, and the potential difference between the normal input voltage and the constant voltage is expressed as an impedance (signal wiring on the printed circuit board). The voltage resulting from dividing the impedance of itself or the impedance of the resistor intentionally provided on the signal wiring) and the impedance between the output terminals of the protection transistor appears at the input terminal, but the input terminal is open abnormally Sometimes, regardless of the normal input voltage, the voltage at the input terminal is the constant voltage. The constant voltage mentioned here is connected to the output terminal of the protection transistor driven to the half-on state, which is different from the one connected to the input terminal of the semiconductor integrated circuit. Line voltage. For this reason, when the protection transistor is driven to a half-on state , the protection transistor is driven so that the voltage at the input terminal differs between when it is normal and when it is abnormally opened.

  On the other hand, if the protection transistor is a MOSFET, the driving means may drive the protection transistor to a half-on state by applying a voltage at which the protection transistor is in a half-on state to the gate of the protection transistor. it can.

  If the protective transistor is a bipolar transistor, the driving means may drive the protective transistor to a half-on state by passing a current that causes the protective transistor to be in a half-on state through the base of the protective transistor. it can.

  If the protection transistor is a MOSFET, the driving means sets the voltage applied to the gate of the protection transistor to an on-voltage (gate-source voltage) that can sufficiently turn on the protection transistor. By performing PWM control such as switching at a predetermined duty ratio between a voltage that can be larger than a threshold voltage) and an off voltage that can completely turn off the protection transistor, the protection transistor is It can be driven to a half-on state. Since there is a parasitic capacitance between the gate and the source of the MOSFET, the protection transistor made of the MOSFET can be driven to a half-on state by performing such PWM control. In addition, describing a modification example of such PWM control, the waveform of the voltage applied to the gate of the MOSFET is not limited to a rectangular wave, but may be a triangular wave or a sawtooth wave. That is, by changing the voltage applied to the gate of the protection transistor at a predetermined cycle, the protection transistor can be driven to a half-on state.

By the way , if the determination means determines, for example, whether or not the voltage of the input terminal when the protection transistor is driven (driven to the half-on state) by the drive means is the constant voltage, If it is determined as an open abnormality and it is determined that the voltage is not the above-described constant voltage, it can be determined as normal.

  However, in general, in order to determine whether or not the voltage is a predetermined value, a certain degree of determination range (determination range) is provided. Therefore, in this configuration, a normal input from the signal wiring of the printed circuit board to the input terminal is usually performed. It is necessary to assume that the input voltage is only a voltage that is a specific value or more away from the constant voltage. On the other hand, if that assumption is not made, when the normal input voltage becomes a voltage that is far from a certain value from the above constant voltage, even if it is actually normal, the protection transistor is driven to the half-on state. Since the difference between the voltage at the input terminal and the constant voltage is very small, there is a possibility of erroneous determination as an open abnormality.

In order to avoid such erroneous determination, the determination unit includes a voltage Va at the input terminal when the drive means is not driving the protection transistor, the input when the driving means is driving the protection transistor It is preferable to configure so as to determine whether there is an open abnormality based on both the terminal voltage Vb.

  More specifically, for example, as a first step, the determination unit determines whether or not the voltage Va at the input terminal when the protection transistor is not driven is a voltage that is a specific value or more away from the constant voltage. If an affirmative determination is made in that determination, as a second step, it is determined whether or not the voltage Vb at the input terminal when the protection transistor is driven is the above-mentioned constant voltage. If an affirmative determination is made, it can be configured to determine an open abnormality.

  When the specific value is Vx, if the normal input voltage is a voltage that is separated from the constant voltage by Vx, the protection transistor is turned on when the normal input voltage is input to the input terminal. Even when driven to the half-on state by the driving means, the voltage of the input terminal is a value that is not determined to be a constant voltage by the determination in the second stage.

Based on the above, the determining means determines whether or not the voltage at the input terminal when the driving means is not driving the protection transistor is a voltage that is not less than a specific value from the constant voltage. If a determination process is performed and an affirmative determination is made in the determination process of the first stage, as a determination process of the second stage, whether the voltage of the input terminal when the driving unit is driving the protection transistor is the constant voltage It may be configured to perform a determination process for determining whether or not, and if an affirmative determination is made in the second-stage determination process, it is determined that an open abnormality has occurred.
In addition, for example, as described above, if the protection transistor is driven to a half-on state as described above, a voltage having a specific correlation with the normal input voltage appears at the input terminal. It is also possible to perform a correlation determination process for determining whether or not there is a specific correlation between the two voltages Va and Vb and to determine that there is an open abnormality. Further, also in this example, before performing the correlation determination process, it is determined whether or not the voltage Va is a voltage separated from the predetermined voltage by a predetermined value or more. If the determination is affirmative, the correlation determination is performed. By performing the processing, it is possible to further increase the accuracy of abnormality determination.
For this reason, the determination means performs a first-stage determination process for determining whether or not the voltage at the input terminal when the drive means is not driving the protection transistor is a voltage that is a specific value or more away from the constant voltage. If the determination result of the first stage is affirmative, the voltage of the input terminal when the drive means is not driving the protection transistor and the drive means drive the protection transistor as the second stage determination process. When the determination process of determining whether or not there is a specific correlation with the voltage of the input terminal at the time of the determination, and it is determined in the determination process of the second stage that there is no correlation, an open abnormality is You may comprise so that it may determine with having generate | occur | produced.

In the semiconductor integrated circuit of the second invention , as the protection transistor, a first protection transistor connected between the input terminal and the power supply voltage line, and a ground voltage line lower than the input terminal and the power supply voltage. And a second protection transistor connected between the two. Generally, these two protection transistors exist at each input terminal of the semiconductor integrated circuit.

  Then, the driving means drives the two protection transistors one by one to the half-on state. Therefore, the determination unit determines that the voltage Vb1 at the input terminal when the driving unit is driving the first protection transistor is the power supply voltage, and the driving unit drives the second protection transistor. If it is determined that the input terminal voltage Vb2 is the ground voltage, it is determined that an open abnormality has occurred.

The semiconductor integrated circuit according to the second aspect of the invention can also correctly determine whether there is an open abnormality regardless of the normal input voltage to the input terminal. That is, the aforementioned erroneous determination can be avoided. For example, if normal, for example, when the normal input voltage is near the power supply voltage, the two protection transistors are sequentially turned on, and it is determined that the voltage Vb1 is the power supply voltage. However, the voltage Vb2 is higher than the ground voltage, and is a voltage obtained by dividing the power supply voltage by the impedance on the signal wiring of the printed circuit board and the impedance of the second protection transistor. It is not misjudged as abnormal.

Note that, for example, the following two configurations are conceivable for the determination unit to determine the voltage of the input terminal.
First, the first configuration is a configuration in which the voltage at the input terminal is detected by AD conversion by an AD converter provided in the semiconductor integrated circuit. And according to this structure, a detailed voltage change can be identified. In the second configuration, the magnitude relationship between the voltage of the input terminal and a predetermined threshold is determined by a comparator (comparator) provided in the semiconductor integrated circuit. According to this configuration, the voltage level can be determined with a simple configuration.

It is a block diagram showing the state which mounted the microcomputer of embodiment on the printed circuit board. It is a graph showing the relationship between the on-resistance of a protection transistor and the gate-source. It is a block diagram explaining the structure of a drive circuit. It is a flowchart showing an abnormality detection process. It is a time chart explaining the effect | action of an abnormality detection process. It is the 1st explanatory view explaining a modification. It is the 2nd explanatory view explaining a modification. It is the 3rd explanatory view explaining a modification.

  A microcomputer (microcomputer) as an IC (semiconductor integrated circuit) according to an embodiment to which the present invention is applied will be described below. Note that the microcomputer according to the present embodiment is a kind of IC in which an electronic circuit made of a semiconductor is enclosed in a single package having a plurality of terminals and collected as a single electronic component.

  As shown in FIG. 1, the microcomputer 21 of this embodiment is mounted on, for example, a printed circuit board 11 that constitutes an electronic control device mounted on a vehicle, and performs a process for realizing a control function performed by the electronic control device. Do.

  Connected to the terminal 15 of the printed circuit board 11 is a sensor 13 whose output voltage changes in a predetermined range in accordance with a physical quantity to be detected (for example, an accelerator operation quantity). The terminal 15 is connected to the input terminal 23 of the microcomputer 21 via the signal wiring 16 formed on the printed board 11.

  However, in this embodiment, in order to prevent the noise superimposed on the sensor signal that is the output voltage of the sensor 13 from being transmitted to the input terminal 23 of the microcomputer 21, a known low-pass filter 17 is provided on the signal wiring 16. Is provided.

  The low-pass filter 17 includes a resistor R1 provided in series with the signal wiring 16, a portion of the signal wiring 16 connecting the resistor R1 and the input terminal 23, and a ground voltage (= 0V) line (hereinafter referred to as a ground line). And a capacitor C1 provided between the two. In the present embodiment, the resistance value of the resistor R1 is, for example, 10 KΩ. In the present embodiment, the sensor signal changes in the range of 1V to 4V if the sensor 13 is normal.

  On the other hand, in addition to the well-known CPU 24 that constitutes the core of the microcomputer 21, ROM, RAM, and the like (not shown), the microcomputer 21 provides an AD converter (ADC) 25 and a plurality of analog signals to the AD converter 25. And a multiplexer (MPX) 27 for selectively switching and inputting.

  In the microcomputer 21, the sensor signal input from the input terminal 23 is input to the AD converter 25 via the multiplexer 27, and AD conversion is performed by the AD converter 25. Further, the AD conversion value that is the AD conversion result of the sensor signal is used by the CPU 24 for predetermined control processing. Note that the microcomputer 21 has a plurality of input terminals for inputting analog signals to be converted into AD, but FIG. 1 shows only the input terminal 23 that is one of the input terminals. .

  Further, in the microcomputer 21, a parasitic diode D1 between the two output terminals is provided between the input terminal 23 and the power supply voltage (5 V in the present embodiment) as a surge voltage protection clamp diode (more specifically, the input terminal A protective transistor T1 that functions as a clamp diode for protecting the internal circuit from a positive surge voltage applied to the capacitor 23 is connected. Similarly, between the input terminal 23 and the ground line, a parasitic diode D2 between the two output terminals is connected to a clamp diode for surge voltage protection (specifically, a negative surge voltage applied to the input terminal 23 from the internal circuit). A protective transistor T2 is connected, which functions as a clamp diode for protecting the signal.

  In the present embodiment, since the chip of the microcomputer 21 is a chip having a CMOS structure, the protection transistor T1 is a P-channel MOSFET, and the protection transistor T2 is an N-channel MOSFET.

  Therefore, in the protection transistor T1, the drain of one of the two output terminals is the input terminal 23 so that the anode of the parasitic diode D1 is on the input terminal 23 side and the cathode of the parasitic diode D1 is on the power supply voltage line side. The source which is the other of the two output terminals is connected to the power supply voltage line. A resistor Rg1 for preventing the protection transistor T1 from being turned on is connected between the gate and the source of the protection transistor T1.

  In addition, the drain of one of the two output terminals of the protection transistor T2 is connected to the input terminal 23 so that the anode of the parasitic diode D2 is on the ground line side and the cathode of the parasitic diode D2 is on the input terminal 23 side. The source which is the other of the two output terminals is connected to the ground line. A resistor Rg2 for preventing the protection transistor T2 from being turned on is also connected between the gate and the source of the protection transistor T2.

In the case of a semiconductor integrated circuit, such a pair of high-side and low-side protection transistors T1 and T2 is provided for each input terminal.
Further, the microcomputer 21 detects one or both of the protection transistors T1 and T2 (in this embodiment, the protection transistor T2 in order to detect an open abnormality in which the input terminal 23 is not connected to the signal wiring 16 of the printed circuit board 11. And a drive circuit 29 for driving the other.

  More specifically, the drive circuit 29 is a circuit that controls the gate voltage VinL of the protection transistor T2, and switches the gate voltage VinL between 0 V and a predetermined half-on drive voltage.

  The protection transistor T2 functions as a normal protection element because the protection transistor T2 is completely turned off when the gate voltage VinL becomes 0V. That is, the parasitic diode D2 functions as a clamp diode.

  On the other hand, the half-on drive voltage output from the drive circuit 29 is a voltage that drives the protection transistor T2 to the half-on state, and is higher than 0 V, but the threshold voltage VT of the protection transistor T2 The voltage is lower than (about 2V). In the present embodiment, as indicated by the dotted line in FIG. 2, the on-resistance (impedance between drain and source) RON-T2 of the protection transistor T2 is the same as the resistance value (= 10 KΩ) of the resistor R1 forming the low-pass filter 17. The gate-source voltage Vgs (= 1.8 V) is set as the half-on drive voltage. Therefore, when the gate voltage VinL becomes the half-on driving voltage, the protection transistor T2 is in a half-on state with an on-resistance of 10 KΩ.

As shown in FIG. 3, the drive circuit 29 includes an analog switch 33, a control register 35, and a selector 37.
The analog switch 33 is turned on to connect the gate of the protection transistor T2 to the half-on drive voltage (= 1.8V) line, and is turned off to disconnect the gate of the protection transistor T2 from the half-on drive voltage line.

  The control register 35 is written by the CPU 24 with 1-bit data indicating whether the analog switch 33 is turned on / off (the protection transistor T2 may be half-on or off).

  If the data in the control register 35 is “1”, for example, the selector 37 turns on the analog switch 33 to set the gate voltage VinL of the protection transistor T2 to a half-on voltage. Then, the protection transistor T2 is driven to a half-on state, and the on-resistance RON-T2 of the protection transistor T2 becomes about 10 KΩ.

  If the data in the control register 35 is “0”, for example, the selector 37 turns off the analog switch 33 and sets the gate voltage VinL of the protection transistor T2 to 0V. Then, the protection transistor T2 is turned off.

  In the present embodiment, the analog switch 33 is an N-channel MOSFET. Therefore, the selector 37 outputs 5V (a voltage higher than the threshold voltage of the analog switch 33) to the gate of the analog switch 33, thereby turning on the analog switch 33 and 0V to the gate of the analog switch 33. Is output to turn off the analog switch 33.

  Further, in the microcomputer 21 of the present embodiment, a half-on driving voltage is input from the outside of the microcomputer 21 via a predetermined voltage input terminal 31, and a line connected to the voltage input terminal 31 is a line of the half-on driving voltage. It has become. For this reason, the analog switch 33 switches the connection / disconnection between the voltage input terminal 31 and the gate of the protection transistor T2.

  Furthermore, in the present embodiment, the operating voltage Vcore of the core (also the CPU 24) in the microcomputer 21 and the half-on driving voltage are the same value of 1.8 V, so the core operating voltage Vcore is input from the outside of the microcomputer 21. The voltage input terminal 31 is a terminal for performing the above. That is, the operating voltage Vcore of the core is used as a half-on drive voltage that the drive circuit 29 supplies to the gate of the protection transistor T2.

  Next, an abnormality detection process executed by the CPU 24 of the microcomputer 21 for detecting an open abnormality of the input terminal 23 will be described with reference to the flowchart of FIG. Note that the abnormality detection process in FIG. 4 is executed at regular intervals, for example.

  As shown in FIG. 4, when the CPU 24 starts executing the abnormality detection process, first, in S110, the AD converter 25 is initialized and “0” is written to the control register 35 to protect the drive circuit 29. The transistor T2 is turned off. Since “0” is also written to the control register 35 by the initialization process executed immediately after the CPU 24 is started, the process of writing “0” to the control register 35 in S110 may be omitted.

  Next, in S120, the multiplexer 27 is switched to input the voltage Vi at the input terminal 23 to the AD converter 25. In FIG. 4, switching the multiplexer 27 so that the voltage Vi at the input terminal 23 is input to the AD converter 25 is described as “MPX ON”.

  In step S130, the AD converter 25 converts the voltage Vi of the input terminal 23 into AD, and in step S140, the multiplexer 27 is switched so that the voltage Vi of the input terminal 23 is not input to the AD converter 25. To. In FIG. 4, switching the multiplexer 27 so that the voltage Vi at the input terminal 23 is not input to the AD converter 25 is described as “MPX off”.

  Next, in S150, the AD conversion value that is the result of AD conversion of the voltage Vi in S130 is stored as “AD0”. For this reason, AD0 indicates the voltage Vi when the protection transistor T2 is not driven (turned off).

  Then, in subsequent S160, it is determined whether or not AD0 is within a range from 2V to 4V (2V ≦ AD0 ≦ 4V). If AD0 is within a range from 2V to 4V, the process proceeds to S170.

  In S170, “1” is written in the control register 35 to cause the drive circuit 29 to drive the protection transistor T2 to a half-on state, and further, the multiplexer 27 is switched so that the voltage Vi of the input terminal 23 is supplied to the AD converter 25. Let them enter. In step S180, the AD converter 25 AD converts the voltage Vi at the input terminal 23.

  Next, in S190, by writing “0” into the control register 35, the protection transistor T2 is returned to the OFF state, and the multiplexer 27 is switched to input the voltage Vi of the input terminal 23 to the AD converter 25. Do not be.

  In subsequent S200, the AD conversion value that is the result of AD conversion of the voltage Vi in S180 is stored as “AD1”, and then the process proceeds to S210. Therefore, AD1 indicates the voltage Vi when the protective transistor T2 is driven to the half-on state.

  In S210, a determination process is performed to determine whether AD1 is 0V. Specifically, it is determined whether or not AD1 is less than a determination value Vth that can be regarded as 0V (in this embodiment, for example, 0.2V). When it is determined that AD1 is not less than the determination value Vth, the abnormality detection process is terminated as it is. However, when it is determined that AD1 is less than the determination value Vth, an open abnormality of the input terminal 23 occurs. The process proceeds to S220, stores that an open abnormality has occurred, and ends the abnormality detection process.

Here, the reason why the presence / absence of the open abnormality can be determined by the determination process of S210 will be described.
First, if it is normal, AD0 becomes the voltage value of the sensor signal, and AD1 sets the voltage value of the sensor signal to the resistance value of the resistor R1 which is the impedance on the signal wiring 16 in the printed circuit board 11 (hereinafter, this resistance value is also referred to). R1) and the on-resistance (hereinafter referred to as RonHF) of the protection transistor T2 driven to the half-on state.

  For this reason, when it is assumed that the voltage value of the sensor signal when the voltage Vi is AD converted in S180 (that is, when the value of AD1 is obtained) and AD0 are the same, AD1 and AD0 have a specific value. As the correlation, there is a relationship of “AD1 = AD0 × RonHF / (R1 + RonHF)”.

In this embodiment, since “R1 = RonHF” is set, if normal, AD1 is half of AD0 (= AD0 / 2).
Further, when the determination process of S210 is performed, it is confirmed by the determination process of S160 prior to that that AD0 is 2V or higher. Therefore, if normal, AD1 should be 1V (= 2V / 2) or higher. It is.

  On the other hand, if an open abnormality of the input terminal 23 has occurred, AD1 becomes about 0 V due to the pull-down action by the protection transistor T2 in the half-on state regardless of AD0.

  Therefore, in S210, it is determined whether AD1 is less than the determination value Vth set between 0V and 1V. If AD1 is less than the determination value Vth, an open abnormality is detected, and if AD1 is not less than the determination value Vth. Judged as normal.

  In other words, if AD0 is smaller than twice the determination value Vth, AD1 will be smaller than the determination value Vth even if it is normal. Although it is normal, it is erroneously determined that an open abnormality has occurred. For this reason, in this embodiment, after confirming that AD1 is larger than twice the determination value Vth in S160, the determination process in S210 is performed. In S160, in order to detect an abnormality of the sensor 13 in S230 described later, it is determined whether AD0 is within a predetermined range. If only the detection of the open abnormality is considered, in S160, AD0 is detected. It is only necessary to determine whether or not is greater than or equal to a predetermined value (or greater than a predetermined value). In S210, it may be determined whether AD1 is equal to or less than a determination value Vth.

On the other hand, if it is determined in S160 that AD0 is not within the range of 2V to 4V, the process proceeds to S230.
In S230, it is determined whether AD0 is less than 1V or greater than 4V, and if it is determined that AD0 is less than 1V, or if AD0 is greater than 4V, sensor 13 is abnormal. And proceed to S240. That is, as described above, since the sensor signal changes within a range of 1V to 4V if it is normal, it is determined that the sensor 13 is abnormal when AD0 is smaller than 1V or larger than 4V. To do.

And in S240, after memorizing that sensor abnormality (abnormality of sensor 13) has occurred, the abnormality detection process is ended.
If it is determined in S230 that AD0 is not less than 1V but not greater than 4V (ie, “1V ≦ AD0 <2V”), the abnormality detection process is terminated.

  According to such an abnormality detection process, as shown on the left side of the time t1 in FIG. 5, when the open abnormality of the input terminal 23 has not occurred, AD1 becomes half of AD0 (≧ 2V) and is determined. Since it is equal to or greater than the value Vth, it is determined to be normal (no open abnormality has occurred). On the other hand, as shown on the right side of the time t1 in FIG. 5, when the open abnormality of the input terminal 23 occurs, AD1 becomes less than the determination value Vth regardless of AD0 (≧ 2V), so the open. It is determined that an abnormality has occurred. Although not shown in FIG. 5, when it is determined that AD0 is less than 1V or AD0 is greater than 4V, it is determined that the sensor 13 itself is abnormal.

  In the microcomputer 21 as described above, the presence or absence of the open abnormality is determined by causing the protection transistor T2 essential for protecting the surge voltage of the input terminal 23 to function as a resistor (pull-down resistor). If it is not determined whether or not there is an open abnormality (period in which the abnormality detection process in FIG. 4 is not performed), an originally unnecessary resistor is connected to the input terminal 23 by leaving the protection transistor T2 off. Can be in a state that is not. Therefore, it is possible to detect an open abnormality of the input terminal 23 while suppressing an additional amount of elements and without affecting the input characteristics.

  In the present embodiment, the voltage (AD0) of the input terminal 23 when the protection transistor T2 is not driven and the voltage (AD1) of the input terminal 23 when the protection transistor T2 is driven to the half-on state. Since the presence / absence of an open abnormality is determined using both, the determination accuracy can be made higher than in a configuration that does not consider AD0.

  However, in the above embodiment, if there is a premise that the voltage input from the outside to the input terminal 23 of the microcomputer 21 is always at least twice as large as the determination value Vth than 0V, the AD0 is not used, and FIG. You may comprise so that the presence or absence of an open abnormality may be determined only by the process of S170-S220.

  In the abnormality detection process of FIG. 4, if “YES” is determined a plurality of times in the determination process of S <b> 210, it may be determined that an open abnormality has occurred. This also applies to the abnormality determination of the sensor 13 performed in S230.

  In the abnormality detection process of FIG. 4, if it is determined that “NO” has been made one or more times in the determination process of S210 after determining that an open abnormality has occurred, the open abnormality has been resolved (ie, normal You may come to judge that it has returned).

  Further, in the abnormality detection process of FIG. 4, the sensor abnormality is also detected, but the sensor abnormality may be detected by another process. In this case, S230 and S240 in FIG. 4 can be deleted. In S160, it is only necessary to determine whether AD0 is equal to or greater than a predetermined value (2 V in the above example), instead of determining the range of AD0.

Note that, among the terminals of the microcomputer 21, the open abnormality can be similarly detected for the input terminals other than the input terminal 23 by the configuration and processing described for the input terminal 23.
Further, the disconnection of the signal wiring 16 on the printed circuit board 11 can also be detected as an open abnormality of the input terminal 23.

  On the other hand, in the above embodiment, the ground voltage (= 0V) corresponds to a constant voltage, and the ground line corresponds to a line having a constant voltage. The drive circuit 29 corresponds to drive means, and the AD converter 25 and the CPU 24 correspond to determination means.

Next, another modification will be described. Note that the modifications described below can be applied in appropriate combinations.
[Modification 1]
In S210 of the abnormality detection process of FIG. 4, a process for determining whether AD1 is “AD0 / 2” is performed as a correlation determination process for determining whether AD1 and AD0 have a specific correlation. If it is determined that AD1 is “AD0 / 2”, it may be determined as normal, and if it is determined that AD1 is not “AD0 / 2”, it is determined as an open abnormality.

  More specifically, the time from AD conversion of the voltage Vi in S130 to AD conversion of the voltage Vi again in S180 (that is, the time from obtaining the value of AD0 to obtaining the value of AD1) within Tint Since the sensor signal can change, the determination value for AD1 should be a value having a certain range, not a single point value (= AD0 / 2).

  For this reason, assuming that a value of half of the maximum change amount that the sensor signal can change within the time Tint is “ΔV”, in S210, it is practically determined whether or not the relationship of the following equation 1 is established. Just do it.

{(AD0 / 2) −ΔV} ≦ AD1 ≦ {(AD0 / 2) + ΔV} Equation 1
If it is determined in S210 that the relationship of Formula 1 is established, it is determined that the relationship is normal, and conversely, if it is determined that the relationship of Formula 1 is not established, an open abnormality occurs. It is good to judge that

In the case of the first modification, in S160, it is better to confirm that AD0 is equal to or greater than a value that does not make an erroneous determination in the process of 210.
That is, when AD0 is a very small value, if the determination process of S210 is performed, “AD0 / 2” becomes smaller than ΔV. Therefore, even if an open abnormality actually occurs and AD1 becomes about 0 V, Equation 1 Therefore, when the AD0 is large enough to prevent such erroneous determination, the determination process in S210 may be performed.

  For example, in the example of FIG. 4, since it is confirmed that AD0 is 2V or more in S160, and the determination process of S210 is performed, if AD1 at the time of an open abnormality is 0.1V, ΔV is If it is not 0.9 V or more, the above-mentioned erroneous determination does not occur. Further, the AD0 range (particularly the lower limit value) determined in S160 may be set from such a viewpoint.

[Modification 2]
As shown in FIG. 6A, the drive circuit 29 is a peripheral voltage in the microcomputer 21 (that is, a peripheral circuit viewed from the CPU 24 as a core, and is used as a power supply voltage for the AD converter 25, I / O, etc.). 5V may be divided into 1.8V by resistors 38 and 39, and the 1.8V may be supplied to the analog switch 33.

Note that the voltage divided by the resistors 38 and 39 can be used not only as the input terminal 23 but also as a half-on drive voltage for other input terminals (not shown).
[Modification 3]
As shown in FIG. 6B, the analog switch 33 of the drive circuit 29 is a terminal different from the above-described voltage input terminal 31 (terminal for inputting the core operating voltage Vcore), and is half-on driven. A voltage may be input from the outside of the microcomputer 21 via the voltage input terminal 41 dedicated to the voltage.

  In this configuration, since the half-on driving voltage applied to the gate of the protection transistor T2 can be changed by the voltage Vtest input to the voltage input terminal 41, the on-resistance of the protection transistor T2 is, for example, 100 KΩ or 1 MΩ. Even when it is desired to change to the resistance value, it can be easily handled.

The voltage Vtest input from the voltage input terminal 41 can be used not only as the input terminal 23 but also as a half-on drive voltage for other input terminals (not shown).
[Modification 4]
As shown in FIG. 6C, the drive circuit 29 performs a PWM control to switch the voltage VinL output to the gate of the protection transistor T2 between 0V and 5V in a predetermined cycle, thereby turning the protection transistor T2 half on. It can also be configured to drive to a state. Since there is a parasitic capacitance between the gate and the source of the MOSFET, the protection transistor T2 made of the MOSFET can be driven to a half-on state by performing such PWM control.

  6C, a P-channel MOSFET is used as the analog switch 33, and 5 V is supplied to the input side (source) of the analog switch 33. Therefore, if the data in the control register 35 is “0”, the selector 37 outputs 5 V to the gate of the analog switch 33, thereby turning off the analog switch 33 and supplying the gate to the protection transistor T2. The voltage VinL is set to 0V. If the data in the control register 35 is “1”, the selector 37 receives the PWM signal output from the PWM signal generation circuit 43 and switches between 0 V and 5 V with a predetermined period and a predetermined duty ratio. The analog switch 33 is output to the gate, and the analog switch 33 is turned on / off to switch the voltage VinL to the gate of the protection transistor T2 between 0V and 5V. In this case, when the PWM signal is 0V, the analog switch 33 is turned on, and the voltage VinL to the protection transistor T2 becomes 5V.

  As shown in FIG. 1, when the capacitor C1 of the low-pass filter 17 is connected to the signal wiring 16 to which the input terminal 23 of the microcomputer 21 is connected, if the protection transistor T2 is turned on, the capacitor C1 Current flows through the protection transistor T2 and the protection transistor T2 is likely to be in a half-on state, so that it is easy to set the PWM control cycle (PWM signal cycle) longer.

Further, the waveform of the voltage applied to the gate of the protection transistor T2 is not limited to a rectangular wave such as a PWM signal, but may be a triangular wave or a sawtooth wave.
[Modification 5]
Although not shown, the configuration of FIG. 6B is further modified so that the voltage Vtest input from the voltage input terminal 41 is supplied to the gate of the protection transistor T2 as it is without passing through the analog switch 33. You may comprise as follows.

  In this case, for example, when a test mode signal is given to the microcomputer 21 during a test after manufacturing the electronic control device, the microcomputer 21 enters the test mode and performs the same processing as in FIG. At this timing, an instruction is given to the outside, and when the instruction is issued, the voltage output circuit on the printed circuit board 11 side outputs a half-on driving voltage to the voltage input terminal 41 of the microcomputer 21. Open abnormality detection of the terminal 23 can be performed. Conversely, when the voltage output circuit on the printed circuit board 11 side switches the voltage output to the voltage input terminal 41 of the microcomputer 21 between 0 V and the half-on drive voltage, the microcomputer 21 is the same as in FIG. 4 according to the switching of the voltage. You may make it progress the process of.

[Modification 6]
As shown in FIG. 7, of the protection transistors T1 and T2, the high-side protection transistor T1 may be driven to a half-on state.

  That is, in the microcomputer 21 shown in FIG. 7, the drive circuit 29 switches the gate voltage VinH of the protection transistor T1 between 5V, which is a voltage for turning off the protection transistor T1, and a half-on drive voltage. Note that the half-on voltage in this case is lower than 5V but higher than “5V−VT” when the threshold voltage of the protection transistor T1 is VT.

Even in this configuration, the open abnormality of the input terminal 23 can be detected by the same processing as in FIG.
Specifically, in S170 of FIG. 4, instead of the protection transistor T2, the protection transistor T1 is driven to a half-on state.

  If it is normal, AD0 obtained by the processing of S110 to S150 becomes the voltage value of the sensor signal, and AD1 obtained by the processing of S170 to S200 is 5V and Vs when the voltage value of the sensor signal is Vs. The potential difference is a value obtained by dividing the potential difference by R1 and the on-resistance RonHF (= R1) of the protection transistor T1, and “AD1 = (5V−Vs) / 2 + Vs”.

  Therefore, assuming that the voltage value Vs of the sensor signal when the value of AD1 is obtained is the same as AD0, AD1 and AD0 have a relationship of “AD1 = (5V−AD0) / 2 + AD0”. is there.

  Further, when the determination process of S210 is performed, it is confirmed by the determination process of S160 prior to that that AD0 is 4 V or less. Therefore, if normal, AD1 is 4.5 V (= (5V-4V) / 2 + 4V) or less.

  On the other hand, if an open abnormality of the input terminal 23 has occurred, AD1 becomes approximately 5V due to the pull-up action by the protection transistor T1 in the half-on state regardless of AD0.

  Therefore, in S210, it is determined whether AD1 is higher than a determination value Vth set between 4.5V and 5V. If AD1 is higher than the determination value, an open abnormality is detected, and AD1 is higher than the determination value Vth. If not, it can be determined as normal.

  In this case, the range of AD0 determined in S160 may be 1V to 4V, and if it is changed as such, S230 can be omitted. If no sensor abnormality is detected in the process of FIG. 4 (that is, S230 and S240 are not performed), in S160, it may be determined whether AD0 is equal to or less than a predetermined value (4 V in the above example). On the other hand, in S210, the presence or absence of an open abnormality may be determined by the same method as in the first modification.

[Modification 7]
As shown in FIG. 8, both the protective transistors T1 and T2 may be used.
Specifically, in the microcomputer 21 of FIG. 8, the CPU 24 causes the drive circuit 29 to drive each of the protection transistors T1 and T2 one by one to the half-on state.

  Then, the CPU 24 AD-converts the voltage Vi at the input terminal when the protection transistor T1 is driven to the half-on state by the AD converter 25, stores the AD conversion value as “ADT1”, and protects the protection transistor T1. The AD converter 25 AD-converts the voltage Vi at the input terminal when the transistor T2 is driven to the half-on state, and stores the AD conversion value as “ADT2”.

  Further, the CPU 24 determines whether or not ADT1 is 5V (actually whether or not it is a determination value slightly lower than 5V) and whether or not ADT2 is 0V ( In practice, if it is determined that ADT1 is 5V and ADT2 is 0V, the input terminal 23 It is determined that an open abnormality has occurred, otherwise it is determined normal.

[Modification 8]
A comparator (comparator) may be provided in the microcomputer 21, and the value of the voltage Vi may be determined by the comparator.

[Others]
By the way, when it is configured to detect an open abnormality of the input terminal 23 using only the protection transistor T2 of the protection transistors T1 and T2, the higher the input voltage to the input terminal 23, the more normal Since the difference in the voltage Vi of the input terminal 23 in the microcomputer 21 becomes large between the time and the open abnormality, it is easy to correctly determine the presence or absence of the open abnormality. For this reason, it can be said that the higher the output voltage of the sensor 13, the higher the open abnormality detection capability (determination capability).

  On the contrary, when the open transistor of the input terminal 23 is detected using only the protective transistor T1 out of the protective transistors T1 and T2, the lower the input voltage to the input terminal 23, Since the difference in the voltage Vi becomes large between the normal time and the open abnormality, it is easy to correctly determine whether there is an open abnormality. For this reason, it can be said that the lower the output voltage of the sensor 13, the higher the detection capability of the open abnormality.

  Here, for example, if the sensor 13 has a higher output voltage as the accelerator operation amount by the vehicle driver is larger, on the microcomputer 21 side, the voltage Vi of the input terminal 23 becomes, for example, the maximum 5V. In addition, it is desired to clarify whether it really represents the accelerator operation amount or a value detected by chance due to an open abnormality of the input terminal 23. This is because if the input terminal 23 becomes high impedance due to an open abnormality, the indefinite voltage Vi of the input terminal 23 accidentally becomes 5V, and is AD-converted, the detection result of the erroneous 5V (= accelerator operation amount) This is because it is not preferable that the maximum detection result) be used for vehicle output control.

  If it is desired to more reliably determine whether or not there is an open abnormality as the output voltage of the sensor 13 is higher, the configuration that detects the open abnormality using the protection transistor T2 of the protection transistors T1 and T2 is used. Is preferably adopted.

  Conversely, if it is desired to more reliably determine whether there is an open abnormality as the output voltage of the sensor 13 is lower, the protection transistor T1 of the protection transistors T1 and T2 is used to detect the open abnormality. It is preferable to adopt a configuration that does this.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to such Embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement in a various aspect. .

  For example, the protection transistor may be a bipolar transistor. In that case, the protection transistor is driven to a half-on state by passing a current that causes the protection transistor to be in a half-on state through the base of the protection transistor. can do.

  Further, the abnormality detection process of FIG. 4 is preferably repeatedly performed during the normal operation of the microcomputer 21, but may be performed also during a test after the electronic control device is manufactured. Alternatively, it may be performed only during a test after the electronic control device is manufactured.

  DESCRIPTION OF SYMBOLS 11 ... Printed circuit board, 13 ... Sensor, 15 ... Terminal, 16 ... Signal wiring, 17 ... Low pass filter, R1 ... Resistance, C1 ... Capacitor, 21 ... Microcomputer, 23 ... Input terminal, 24 ... CPU, T1, T2 ... Protection Transistor, D1, D2 ... Parasitic diode, Rg1, Rg2 ... Resistance, 25 ... AD converter, 27 ... Multiplexer, 29 ... Drive circuit, 31 ... Voltage input terminal, 33 ... Analog switch, 35 ... Control register, 37 ... Selector, 38, 39 ... resistors, 41 ... voltage input terminals, 43 ... PWM signal generation circuit

Claims (3)

The input terminal is mounted on the printed circuit board and connected to the signal wiring formed on the printed circuit board to input a signal from the signal wiring.
Further, a semiconductor integrated circuit is connected between the input terminal and the constant voltage line, wherein a protection transistor is connected, in which a parasitic diode between two output terminals functions as a clamp diode for surge voltage protection. ,
The protection transistor is half-on so that the voltage at the input terminal is different between when the input terminal is connected to the signal line and when the input terminal is not connected to the signal line. Driving means for driving to a state;
Based on both the voltage at the input terminal when the drive means is not driving the protection transistor and the voltage at the input terminal when the drive means is driving the protection transistor, Determination means for determining presence or absence of the open abnormality;
With
The determination means includes
Performing a first stage determination process for determining whether or not the voltage of the input terminal when the driving means is not driving the protection transistor is a voltage that is a specific value or more away from the constant voltage; If an affirmative determination is made in the one-step determination process, it is determined as a second-step determination process whether or not the voltage at the input terminal when the driving means is driving the protection transistor is the constant voltage. If the determination process in the second stage is affirmatively determined, it is determined that the open abnormality has occurred.
A semiconductor integrated circuit. The input terminal is mounted on the printed circuit board and connected to the signal wiring formed on the printed circuit board to input a signal from the signal wiring.
Further, a semiconductor integrated circuit is connected between the input terminal and the constant voltage line, wherein a protection transistor is connected, in which a parasitic diode between two output terminals functions as a clamp diode for surge voltage protection. ,
The protection transistor is half-on so that the voltage at the input terminal is different between when the input terminal is connected to the signal line and when the input terminal is not connected to the signal line. Driving means for driving to a state;
Based on both the voltage at the input terminal when the drive means is not driving the protection transistor and the voltage at the input terminal when the drive means is driving the protection transistor, Determination means for determining presence or absence of the open abnormality;
With
The determination means includes
Performing a first stage determination process for determining whether or not the voltage of the input terminal when the driving means is not driving the protection transistor is a voltage that is a specific value or more away from the constant voltage; If an affirmative determination is made in the one-step determination process, as the second-step determination process, the voltage of the input terminal when the drive means is not driving the protection transistor, and the drive means determines the protection transistor. When the determination process of determining whether or not there is a specific correlation with the voltage of the input terminal when driving, if it is determined in the determination process of the second stage that there is no correlation, Determining that an open error has occurred;
A semiconductor integrated circuit. The semiconductor integrated circuit according to claim 1 or 2,
The signal input to the input terminal from the signal wiring is a sensor signal whose voltage value changes within a predetermined range,
The semiconductor integrated circuit is
It is determined whether the voltage of the input terminal when the driving means is not driving the protection transistor is out of the predetermined range, and when it is determined that the voltage is out of the predetermined range, Comprising a sensor abnormality detection means for determining that a sensor that outputs a sensor signal is abnormal;
A semiconductor integrated circuit .

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