JP4671927B2 - Semiconductor device - Google Patents

Description

  The present invention relates to a semiconductor device including a voltage detection circuit that detects an operating state of an input voltage, and more particularly to a semiconductor device including a voltage detection circuit that reduces power loss when a high voltage is applied.

  As shown in FIG. 8, the conventional voltage detection circuit compares the detection voltage Vd obtained by dividing the input voltage Vin and the ground potential by resistors Ra and Rb with the reference voltage Vr by the comparator 105, In general, the state of the input voltage Vin is detected by detecting the output signal Vo.

  9A is a graph showing the relationship between the input voltage Vin and the detection voltage Vd in the equivalent circuit of the voltage detection circuit shown in FIG. 8, and FIG. 9B is a graph showing the input voltage Vin and the input current Iin. It is the graph which showed this relationship.

  FIG. 10 is a cross-sectional view when the resistors Ra and Rb are formed in the semiconductor substrate. An N-type buried layer 111 is formed in a P-type silicon substrate 110, and resistors Ra and Rb are constituted by P-type diffusion layers 102 and 103 formed in the buried layer 111. The input voltage Vin is applied to the electrode 113 formed at one end of the P-type diffusion layer 102, and the electrode 116 formed at one end of the P-type diffusion layer 103 is connected to the ground potential. The electrodes 114 and 115 formed at the other ends of the P-type diffusion layers 102 and 103 are connected to each other to output a detection voltage Vd and input to the comparator 105.

Here, the detection voltage Vd obtained by resistance division is assumed to be Vin.
Vd = Vin × Rb / (Ra + Rb)
When the detection voltage Vd becomes equal to or higher than the reference voltage Vr, the output signal Vo of the comparator 105 changes from “L” to “H”, thereby detecting the operation state of the input voltage Vin.

At this time, at the point where voltage detection is performed (Vd = Vr),
Vin = Vr × (Ra + Rb) / Rb, and the input current Iin is
Iin = Vr / Rb.

  By the way, in the voltage detection circuit that generates the detection signal Vd by resistance division, in consideration of the maximum input voltage Vin, the resistance element includes, for example, a plurality of resistors so that the voltage applied to both ends of each resistor is equal to or lower than the withstand voltage. It is designed such that it is composed of resistors. In addition, in order to increase detection accuracy, the voltage dependence of the resistance value is designed to be as small as possible. As a result, as shown in FIG. 9B, even after the input voltage Vin rises, the detection voltage Vd exceeds the reference voltage Vr, and the output signal Vo of the comparator 105 is inverted, the input current Iin is As the voltage Vin increases, power loss occurs.

  For example, when the detection voltage Vd is set so that the stop state is maintained until the input voltage Vin reaches a predetermined threshold voltage Vt at the time of start-up (low input voltage detection), the input voltage Vin is the threshold value. When the value voltage Vt is exceeded and the normal operating voltage is reached, a current from a high voltage constantly flows through the dividing resistor, causing a problem of power loss. In particular, when the input voltage Vin during normal operation is larger than the predetermined threshold voltage Vt, the input current Iin until the input voltage Vin reaches the predetermined threshold voltage Vt does not matter. Even if it is as small as possible, the power loss accompanying the increase in the input current Iin during normal operation becomes so large that it cannot be ignored.

  In order to suppress this power loss, it is conceivable to increase the resistance value to reduce the current value. However, in the case where the resistance element is constituted by a diffused resistor as shown in FIG. 10, in order to obtain a necessary resistance value. Requires a very large area. As a result, in the semiconductor device in which the voltage detection circuit is mounted on the semiconductor substrate, the size of the device is increased, which does not solve the problem.

  As a method for solving such a problem, Patent Document 1 discloses that a resistance element is formed by a PN junction formed on a semiconductor substrate, an input voltage is applied to the PN junction with a reverse bias, and a resistance due to a change in a depletion layer of the PN junction. A technique for detecting a voltage of an input voltage by measuring a change amount of the value is disclosed.

According to this method, since the input voltage is applied to the PN junction with a reverse bias, only a leakage current flows through the resistance element, and as a result, almost no power loss occurs in voltage detection. In addition, since the size of the resistance value is not limited, it is not necessary to increase the area of the resistance element constituted by the PN junction, and the semiconductor device is enlarged even when the voltage detection circuit is mounted on the semiconductor substrate. There is no problem.
JP-A-4-261038

  The method described in Patent Document 1 is useful in terms of reducing power loss without increasing the size of a semiconductor device equipped with a voltage detection circuit, but has the following problems.

  That is, in the voltage detection circuit, the accuracy of voltage detection is inherently required, and for this purpose, as shown in FIG. 9A, the relationship between the input voltage Vin and the detection voltage Vd is linear. Is preferred. Therefore, conventionally, when the detection voltage Vd is set by resistance division as shown in FIG. 8, the resistance element is designed so that the voltage dependence of the resistance value becomes as small as possible.

  On the other hand, since the resistance element described in Patent Document 1 obtains a change in resistance value due to a change in the depletion layer of the PN junction, the detection voltage Vd cannot be changed linearly with respect to the input voltage Vin. . Further, when the PN junction is formed, if the diffusion depth or concentration of the diffusion layer formed on the semiconductor substrate varies, the variation of the depletion layer also varies, so that the voltage detection accuracy decreases. In addition, the characteristics of the voltage detection circuit mounted on the semiconductor device manufactured in the mass production process also vary, leading to a decrease in reliability.

  The present invention has been made in view of such a point, and a main object thereof is to provide a semiconductor device including a voltage detection circuit in which power loss is reduced when a high voltage is applied.

  In order to achieve the above object, a semiconductor device according to the present invention employs a configuration in which a current limiting element is provided between an input terminal for inputting an input voltage and an output terminal for outputting a detected voltage in a voltage detection circuit.

  Here, the current limiting element is composed of a diffusion layer having a PN junction formed in a semiconductor substrate, and when the voltage applied to one end of the diffusion layer exceeds a specified voltage, the diffusion layer is depleted by depletion of the PN junction. The current flowing is limited.

That is, a semiconductor device according to the present invention is a semiconductor device provided with a voltage detection circuit that detects an operating state of an input voltage by detecting a detection voltage that is uniquely set with respect to the input voltage. The detection circuit includes an input terminal for inputting an input voltage, an output terminal for outputting the detection voltage, and a current limiting element connected between the input terminal and the output terminal. The current limiting element is provided in the semiconductor substrate. When the input voltage applied to one end of the diffusion layer exceeds the specified voltage, the current flowing through the diffusion layer is limited due to depletion of the PN junction. and, the detection voltage when the input voltage is the specified voltage, setting the detection voltage of the input voltage to the specified voltage is uniquely set by resistance division by a plurality of resistors connected to the input terminal Is set to be lower, and, in the following settings detection voltage, the current flowing through the diffusion layer of the current limiting element is characterized in that not restricted.

  According to such a configuration, since the input current is limited by the current limiting element after the input voltage exceeds the specified voltage with respect to the increase of the input voltage, the power loss accompanying the increase of the input voltage is suppressed. be able to. Further, since the detection voltage is set to a voltage that is uniquely set with respect to a specified voltage that limits the current flowing through the current limiting element (hereinafter referred to as a set detection voltage), the detection voltage is set to the set detection voltage. In the meantime, the input current is not limited by the current limiting element, and the accuracy of voltage detection is not reduced.

  In a preferred embodiment, the current limiting element is composed of a JFET element formed in a semiconductor substrate, and the specified voltage is a pinch-off voltage of the JFET element.

  As a result, the input current can be surely limited above the pinch-off voltage (specified voltage), and the linearity between the input voltage and the detection voltage can be maintained below the pinch-off voltage. Can be detected.

  The current limiting element may be formed of a diffused resistor formed in a semiconductor substrate, and the diffused resistor is formed in an opposite conductivity type buried layer provided in a one conductivity type semiconductor substrate. A high potential voltage on the input terminal side is applied to one end of the diffusion layer and the buried layer.

  As a result, the current limiting element can also serve as a resistance element that uniquely sets the detection voltage with respect to the input voltage, so that the semiconductor device including the voltage detection circuit can be made smaller.

  Here, it is preferable that the detection voltage is uniquely set by dividing the input voltage by a plurality of resistors connected to the input terminal.

  Moreover, at least one of the plurality of resistors may constitute the current limiting element.

  Furthermore, the operation state of the input voltage may be detected by comparing the detection voltage with a reference voltage.

  According to the semiconductor device of the present invention, until the input voltage detection voltage exceeds the reference voltage, the input voltage can be detected without degrading the detection accuracy, and the input voltage is detected against the increase. After the voltage exceeds the reference voltage, power loss accompanying an increase in input voltage can be suppressed, whereby a semiconductor device including a voltage detection circuit with low power consumption can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, components having substantially the same function are denoted by the same reference numerals for the sake of simplicity. In addition, this invention is not limited to the following embodiment.

(First embodiment)
FIG. 1 is an equivalent circuit diagram of a voltage detection circuit 10 mounted on a semiconductor device according to the first embodiment of the present invention.

  As shown in FIG. 1, the voltage detection circuit 10 includes an input terminal 11 that inputs an input voltage Vin, an output terminal 12 that outputs a detection voltage Vd that is uniquely set with respect to the input voltage Vin, and an input terminal 11. A current limiting element 13 connected to the output terminal 12 is provided. Then, the operating state of the input voltage Vin is detected by detecting the detection voltage Vd (for example, by comparing the detection voltage Vd with the reference voltage Vr).

The detection voltage Vd is obtained by dividing the output voltage Vj of the current limiting element 13 by resistors Ra and Rb connected to the input terminal 11.
V d = V j × Rb / (Ra + Rb) (1)
It can be set uniquely based on the formula of Here, since Vin and Vj have a unique relationship depending on the characteristics of the current limiting element 13, the detection voltage Vd is determined by a unique relationship with respect to the input voltage Vin.

  Further, when the detection voltage Vd and the reference voltage Vr are input to the comparator 14 and the detection voltage Vd becomes equal to or higher than the reference voltage Vr, the output signal Vo of the comparator 14 changes from “L” to “H”. The operating state of the input voltage Vin can be detected.

  Here, the current limiting element 13 is composed of a diffusion layer having a PN junction formed in a semiconductor substrate, and when the voltage applied to one end of the diffusion layer on the input terminal 11 side becomes equal to or higher than a predetermined voltage. The current flowing through the diffusion layer is limited by depletion of the PN junction. In the present embodiment, a JFET element is employed as the current limiting element 13.

  FIG. 2 is a graph showing voltage characteristics of the output voltage Vj with respect to the input voltage Vin of the JFET element 13. As shown by the characteristics of the JFET element 13 shown in FIG. 2, as the input voltage Vin increases, the output voltage Vj of the JFET element 13 also increases, and when the specified voltage (pinch-off voltage) Vps is reached, the JFET element 13 is pinched off. As a result, the increase in the output voltage Vj is reduced, and thereafter, the output voltage Vj is fixed to the constant voltage Vpf.

  FIG. 3A is a plan view showing the configuration of the JFET element 13, and FIG. 3B is a cross-sectional view taken along the line IIIb-IIIb in FIG.

  As shown in FIG. 3B, the JFET element 13 includes a P-type gate diffusion layer 23 and N + -type source / drain diffusions in an N-type diffusion layer 22 formed on a P-type semiconductor substrate 21. The layers 24 and 25 are formed. The P-type gate diffusion layer 23 is connected to the ground potential, the drain diffusion layer 25 is connected to the input terminal 11 of the input voltage Vin via the electrode 27, and the output voltage Vj of the JFET element 13 is applied to the source diffusion layer 24. Output from the electrode 26.

  As is well known, when the input voltage Vin reaches the pinch-off voltage Vps, the channel (N-type diffusion layer 22) formed between the source diffusion layer 24 and the drain diffusion layer 25 is connected to the P-type gate diffusion layer 23 and the N-type diffusion layer. The PN junction constituted by the diffusion layer 22 and / or the PN junction constituted by the N-type diffusion layer 22 and the P-type semiconductor substrate 21 is depleted, so that the channel is cut off and flows through the channel at a pinch-off voltage Vps or higher. Current is limited. As a result, as shown in FIG. 2, the output voltage Vj of the JFET element 13 is fixed to a constant voltage Vpf.

  As described above, by providing the current limiting element (JFET element) 13 between the input terminal 11 for inputting the input voltage Vin and the output terminal 12 for outputting the detection voltage Vd, the input voltage Vin is prevented from increasing. After the specified voltage (pinch-off voltage Vps) is exceeded, the input current Iin is limited by the current limiting element 13, so that it is possible to suppress power loss accompanying the increase in the input voltage Vin. Further, since the input current is not limited by the current limiting element until the detection voltage exceeds the reference voltage, the accuracy of voltage detection does not decrease.

  In this case, the detection voltage Vd needs to be set to be equal to or lower than a voltage that is uniquely set with respect to the specified voltage Vps when the input voltage Vin is the specified voltage Vps according to the equation (1).

  In the semiconductor device including the voltage detection circuit according to the present invention, for example, when the detection voltage Vd is set so as to maintain the stop state until the input voltage Vin reaches a predetermined threshold voltage Vt at the time of startup. (Low input voltage detection) is particularly effective when the input voltage Vin during normal operation is larger than the predetermined threshold voltage Vt. For example, when the threshold voltage Vt is set to 60 V and the input voltage Vin during normal operation is 80 to 270 V, the power loss due to the voltage detection circuit is reduced by about several hundreds mW (90%) by using the present invention. can do.

  Further, when the voltage detection circuit according to the present invention is used as a circuit for detecting a voltage drop of a battery or the like, for example, the power consumption of the voltage drop detection circuit can be minimized. Can be used continuously.

  Further, it detects that the input voltage has risen to a predetermined voltage (for example, 110 VAC) or more so that the product corresponding to the power supply for Japan (100 VAC) is used overseas (200 VAC). By using it as a voltage detection circuit, it is possible to reduce the power loss when the high input operation is stopped.

  In the configuration of the JFET element 13 shown in FIG. 3B, the gate diffusion layer 23 may be formed so as to be embedded in the N-type diffusion layer 22 as shown in FIG. In this way, when a high voltage is applied to the input voltage Vin, the depletion layer extends both above and below the gate diffusion layer 23, so that pinch-off can be efficiently generated.

(Second Embodiment)
In the first embodiment of the present invention, the case where a JFET element is used as the current limiting element 13 has been described. However, in this embodiment, an example in which the current limiting element 13 is configured by a diffused resistor formed in a semiconductor substrate. Will be described with reference to FIG.

  FIG. 5A is a plan view showing the configuration of the current limiting element 13 in the second embodiment of the present invention, and FIG. 5B is a cross-sectional view taken along the line Vb-Vb in FIG. FIG.

  As shown in FIG. 5B, the current limiting element 13 in this embodiment is a P-type diffusion layer 33 formed in an N-type buried layer 32 provided in a P-type semiconductor substrate 31. It is configured. A high potential voltage on the input terminal 11 side is applied to one end (P + contact region 35) of the P-type diffusion layer 33 and one end (N + contact region 36) of the N-type buried layer 32 via the electrodes 38 and 39. VR1 is applied, and the resistance output voltage VR2 is output from the electrode 37 at the other end (P + contact region 34) of the P-type diffusion layer 33.

  FIG. 6 is a graph showing the current characteristic IR of the diffused resistor 33 with respect to the voltage (ΔVR = VR1−VR2; VR1> VR2) applied across the diffused resistor 33.

  As shown in FIG. 6, the current IR flowing through the diffusion resistor 33 increases as the voltage ΔVR applied to both ends of the diffusion resistor 33 increases. However, when the voltage IR exceeds the specified voltage Vpr, the current IR flowing through the diffusion resistor 33 is Saturates gradually. This is because the current flowing through the P-type diffusion layer 33 is limited by depletion of the PN junction formed by the N-type buried layer 32 and the P-type diffusion layer 33 as the voltage ΔVR increases. It is.

  As a result, the input current Iin is limited by the current limiting element (diffusion resistor) 13 after the input voltage Vin exceeds the specified voltage Vpr with respect to the increase, thereby suppressing the power loss accompanying the increase in the input voltage Vin. can do. Further, since the input current is not limited by the current limiting element until the detection voltage exceeds the reference voltage, the accuracy of voltage detection does not decrease.

  Since the current limiting element (diffusion resistor) 13 in this embodiment can also serve as at least one resistance element of the divided resistors Ra and Rb shown in FIG. 1, the semiconductor device including the voltage detection circuit can be made smaller. be able to.

  5B, the P-type diffusion layer 33 may be formed so as to be embedded in the N-type buried layer 32 as shown in FIG. In this way, when a high voltage is applied to the input voltage Vin, the depletion layer spreads both above and below the P-type diffusion layer 33, so that the current limiting characteristic of the diffusion resistor 33 can be obtained efficiently. In addition, since the diffused resistor 33 is embedded in the N-type buried layer 32, the diffused resistor 33 is hardly affected by the oxide film formed on the surface of the substrate, and is effective in stabilizing the resistance value.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible. For example, in the above embodiment, the JFET element functioning as the current limiting element 13 and the diffused resistor have been described, but these may be used in combination. Further, although the diffusion resistor 13 is the P-type diffusion layer 33, even if it is an N-type diffusion layer, the same effect can be obtained by making the semiconductor substrate 31 N-type and the buried layer 32 P-type. be able to. Furthermore, even if the current limiting element 13 is further provided between the output terminal 12 that outputs the detection voltage and the ground potential, the effect of the present invention can be obtained.

  The present invention is effective for a semiconductor device including a voltage detection circuit to which a high voltage is applied.

It is an equivalent circuit diagram of the voltage detection circuit mounted in the semiconductor device in the first embodiment of the present invention. It is the graph which showed the voltage characteristic of the output voltage with respect to the input voltage of the JFET element in the 1st Embodiment of this invention. It is the figure which showed the structure of JFET in the 1st Embodiment of this invention, (a) is the top view, (b) is the sectional drawing. It is sectional drawing which showed the other structure of JFET in the 1st Embodiment of this invention. It is the figure which showed the structure of the diffused resistance in the 2nd Embodiment of this invention, (a) is the top view, (b) is the sectional drawing. It is the graph which showed the voltage-current characteristic of the diffused resistance in the 2nd Embodiment of this invention. It is sectional drawing which showed the other structure of the diffused resistance in the 2nd Embodiment of this invention. It is an equivalent circuit diagram of a conventional voltage detection circuit. FIG. 4 is a graph showing characteristics in a conventional voltage detection circuit, where (a) is a graph showing the relationship between the input voltage and the detection voltage, and (b) is a graph showing the relationship between the input voltage and the input current. . It is sectional drawing which showed the structure of the semiconductor device carrying the conventional voltage detection circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Voltage detection circuit 11 Input terminal 12 Output terminal 13 Current limiting element (JFET element, diffused resistance)
14 Comparator 21 Semiconductor substrate 22 N-type diffusion layer 23 P-type gate diffusion layer 24 Source diffusion layer 25 Drain diffusion layer 26, 27 Electrode 31 Semiconductor substrate 32 N-type buried layer 33 P-type diffusion layer 34, 35, 36 Contact region 37, 38, 39 electrodes

Claims (7)

A semiconductor device including a voltage detection circuit that detects an operation state of the input voltage by detecting a detection voltage uniquely set with respect to the input voltage,
The voltage detection circuit includes:
An input terminal for inputting the input voltage;
An output terminal for outputting the detection voltage;
A current limiting element connected between the input terminal and the output terminal,
The current limiting element is:
A diffusion layer having a PN junction formed in a semiconductor substrate, and
When the input voltage applied to one end of the diffusion layer exceeds a specified voltage, the current flowing through the diffusion layer is limited due to depletion of the PN junction,
The detection voltage is uniquely set by dividing the input voltage by a plurality of resistors connected to the input terminal with respect to the specified voltage when the input voltage is the specified voltage. A semiconductor device, wherein the semiconductor device is set to be equal to or lower than a detection voltage, and a current flowing through the diffusion layer of the current limiting element is not limited below the set detection voltage. The current limiting element is composed of a JFET element formed in the semiconductor substrate,
The semiconductor device according to claim 1, wherein the specified voltage is a pinch-off voltage of the JFET element. The current limiting element is composed of a diffused resistor formed in the semiconductor substrate,
The diffusion resistance is
It is composed of a diffusion layer of one conductivity type formed in a buried layer of reverse conductivity type provided in a semiconductor substrate of one conductivity type,
2. The semiconductor device according to claim 1, wherein a high potential voltage on the input terminal side is applied to one end of the diffusion layer and the buried layer. Wherein at least one of the plurality of resistors, characterized in that it constitutes the current limiting element, a semiconductor device according to claim 1. Wherein by comparing the reference voltage to detect voltage, and detects the operating state of the input voltage, the semiconductor device according to any one of claims 1-4. The input voltage is characterized by a power supply voltage, the semiconductor device according to any one of claims 1-4.   2. The semiconductor device according to claim 1, wherein the voltage detection circuit further includes the current limiting element between an output terminal that outputs the detection voltage and a ground potential.

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