JPH05241671A - Reference voltage generator and semiconductor with function preventing excess current - Google Patents

Abstract

(57) [Abstract] [Purpose] In the overcurrent prevention circuit mounted on intelligent power switches, etc., the resistance for overcurrent judgment is manufactured by diffusion, so its resistance value depends on temperature and manufacturing. There is variation above. Therefore, it is possible to realize a semiconductor device capable of accurately demonstrating whether or not an overcurrent is present by compensating for variations due to temperature dependence and manufacturing variations, and preventing the overcurrent while sufficiently exhibiting the ability of the switch. [Configuration] Zener diode 3 having positive temperature dependence
02 and a diode PN junction 303 to 305 having a negative temperature dependence, and controlling their contribution to the reference voltage by the ratio of the resistance values of the resistors 306 and 307. The voltage Vref0 can be generated, and by using this reference voltage, it is possible to accurately determine the current value by compensating the variation in the resistance value due to the temperature of the monitor resistor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference voltage generator for supplying a reference voltage to be referred to when judging voltage, current, etc. by a resistance having temperature dependency, and an overcurrent using this reference voltage generator. The present invention relates to a semiconductor device having a function of preventing the above.

[0002]

2. Description of the Related Art In recent years, a power MOSFET and a logic / analog circuit have been integrated into a single chip, and an intelligent power switch capable of performing load state detection, abnormality detection, element protection control, etc. while having a low on-resistance output ( IPS) is under development.

Semiconductor devices having such a protection function are mainly used for automobiles and power supplies. One of the protection functions is a protection function against overcurrent.

FIG. 5 shows an output power MOSFET 101.
A conventional overcurrent protection circuit without IPS is shown, including This circuit can protect the switching element such as the power MOSFET from a short-circuit failure to the power supply of the output terminal of the IPS or from the inflow of an overcurrent due to a load abnormality. The loads considered here include inductance, resistance, and capacitor.

In the IPS of FIG. 5, the output power MO
The SFET 101 is driven by the gate drive circuit 105. The output current flowing through the output power MOSFET 101 is monitored by the current monitoring MOSFET 102 which is also driven by the gate drive circuit 105. This monitor MOSFET 102 is
It is formed by the same manufacturing method as the power MOSFET 101, and has the same structure. However, the channel width is reduced in order to increase the on-resistance by several tens to several hundreds of thousands. Further, the monitor MOSFET 102 has a load terminal P to which the power MOSFET 101 is connected.
1 and P2. Therefore, this monitor MO
The SFET 102 is used to detect a minute current so that the current flowing through the main path of the power MOSFET 101 can be monitored.

A monitor resistor 103 for measuring overcurrent is connected in series to the monitor MOSFET 102. The voltage drop N1 in the monitor resistor 103 is
It is applied to an inverter composed of a depletion type load MOSFET 107 and a detection MOSFET 108. MOSFET 107 and 108
The output result of the inverter constituted by the
09 gate electrode. This current limiting MOS
The FET 109 includes the gate drive circuit 105, the power MOSFET 101, and the monitor MOSFET 10.
2 is connected so that the driving signal potential N2 applied to each gate electrode can be lowered. Therefore,
In this circuit, first, the power MOS which is the main path
When the current flowing through the FET 101 increases, the monitor MO
The current flowing through the SFET 102 also increases, and the monitor resistor 1
The voltage drop N1 at 03 also increases. When the current flowing through the main path exceeds a certain value, the voltage drop N1 becomes MO
The threshold potential of the inverter constituted by the SFETs 107 and 108 is exceeded, and as a result, the MOSFET 109 becomes conductive via the inverter 106. For this reason, the level N2 of the drive signal from the gate drive circuit 105 is lowered, the current flowing through the main path is limited, and the overcurrent can be prevented from flowing.

[0007]

However, such an I
In PS, the monitor resistor 103 is formed as a diffused resistor on the semiconductor substrate in order to detect an overcurrent, so that the resistance value has a considerably large temperature dependency. The same applies to the threshold value of the inverter formed by the MOSFETs 107 and 108, but the resistance value shows a considerably large temperature dependence of 2000 ppm / ° C or more. For this reason, the temperature dependence of the limiting current value, which flows through the monitoring MOSFET 102 and is determined by the voltage drop N2 of the monitoring resistor 103, becomes considerably large.
There is a problem in that the function of preventing the power MOSFET 101 from overcurrent is degraded due to temperature.

Further, since the monitor resistor 103 is formed as a diffusion resistance on the semiconductor substrate, there is a manufacturing variation and the resistance value also varies. Therefore, the amount of voltage drop in the monitor resistor 103 also varies, and the limiting current value that protects the power MOSFET 101 from overcurrent also varies. This is the detection MOSFET 10 to which the voltage drop of the monitor resistor 103 is applied.
The same applies to No. 8 and there is a problem that the threshold voltage of the MOSFET 108 varies due to manufacturing variations.

Therefore, in the present invention, the above temperature,
Alternatively, another object of the present invention is to realize a semiconductor device having a more accurate overcurrent protection function by preventing fluctuations in the limiting current due to manufacturing variations.

[0010]

In order to solve the above problems, in the present invention, a reference voltage generator having a temperature compensation function is used to eliminate the temperature dependence of the limited current,
Further, the reference voltage is set by a circuit made by the same manufacturing process as the monitor resistor and the like, so that the influence of manufacturing variations is suppressed. That is, at least one constant voltage drop means and two or more resistance means connected in series to the constant voltage generation means according to the present invention are provided, and the voltage value divided by these resistance means can be referred to as a reference voltage. In a reference voltage generator having a simple reference voltage generator, a temperature-dependent constant voltage generating means having a monotonic temperature dependence of the generated voltage is used as the constant voltage generating means, and a temperature dependence of the falling voltage is used as the constant voltage lowering means. The temperature-dependent constant voltage drop means, which has the opposite tendency to the constant voltage generation means and is monotonous, is used, and the resistance means is a specific resistance means capable of setting the ratio of the resistance values of these two or more resistance means. It is characterized by As the temperature-dependent constant voltage generating means,
A load element having a constant current function connected to the power supply potential,
It is desirable to employ a circuit composed of this load element and a Zener diode connected in series, and the anode of the Zener diode is connected to the ground potential.

As the temperature-dependent constant voltage drop means, it is effective to use at least one of the voltage drop between the base and emitter of the bipolar transistor and the forward voltage drop of the diode.

Further, in a reference voltage generator having a reference current control MISFET for generating a reference current having a predetermined current value and a reference resistance means capable of referring to a voltage drop due to this reference current as a reference voltage, It is effective to apply the reference voltage from the reference voltage generating unit to the gate potential of the reference current control MISFET.

Further, a monitor MISFET for detecting an overcurrent passing through the switching element and the monitor MISFET.
In a semiconductor device with an overcurrent prevention function, which has a monitoring resistance means connected in series with an FET and a determination means for comparing a voltage drop value in the monitoring resistance means with a reference voltage to detect an overcurrent, It is effective to have the above-mentioned reference voltage generator and use the reference voltage from the reference voltage generator as the reference voltage.

When a reference voltage generator having a reference current control MISFET and a reference resistance means is used, the reference current control MISFET is a monitor MISFET.
It is desirable to use the same process MISFET formed on the semiconductor substrate by the same process as the SFET and the same process MISFET formed on the semiconductor substrate by the same process as the monitor resistance unit as the reference resistance unit. Then, it is effective to connect the reference current control MISFET and the monitor MISFET in parallel.

[0015]

The temperature-dependent constant voltage generating means having such a monotonic temperature dependency of the generated voltage, and the temperature-dependent constant voltage lowering means having a monotonous temperature dependency of the voltage drop as opposed to the constant voltage generating means, In the reference voltage generation means using the specific resistance means capable of setting the resistance value ratio, the reference voltage having a predetermined temperature dependency can be generated by adjusting the resistance value ratio. Therefore, even if the voltage to be compared has temperature dependence, it is possible to generate the reference voltage that matches the temperature dependence of the comparison target. Therefore, it is possible to generate the reference voltage when the voltage is determined by removing the error due to the temperature. A Zener diode to which a constant current is applied by a load element can be used as a highly accurate temperature-dependent constant voltage generating means with a positive temperature dependence, and an accuracy with a negative temperature dependence. As a good temperature-dependent constant voltage drop means, a voltage drop between the base and emitter of a bipolar transistor and a forward voltage drop of a diode can be adopted.

Therefore, by comparing the reference voltage whose temperature dependence can be controlled with the overcurrent monitoring voltage drop value from the monitoring resistance means, the resistance value in the monitoring resistance means changes to the temperature. Even if it fluctuates dependently, the fluctuation can be compensated and the overcurrent can be accurately monitored.

Further, by controlling the reference current controlling MISFET with the reference voltage having such temperature dependency, it is possible to eliminate the temperature dependency in the current control of the reference current controlling MISFET. Therefore, a constant current that does not depend on temperature can be supplied from the reference current control MISFET to the reference resistance means, and the voltage drop in the reference resistance means can be used as the reference voltage. When the reference resistance means and the monitor resistance means are formed by the same process, both resistance means have the same temperature dependence, so that the overcurrent monitoring voltage generated from the monitor resistance means is generated. By determining the drop value based on the reference voltage, it is possible to prevent the occurrence of an error due to temperature, and it is possible to accurately compare the overcurrent limit value and the current value that is actually flowing. Therefore, in the semiconductor device with an overcurrent prevention function having such a configuration, the overcurrent can be determined by excluding the influence of temperature deviation and manufacturing variations, and this circuit can be reliably protected from the overcurrent. Further, a reference current control MISFET and a monitor MISFET are manufactured by the same process, and by connecting them in parallel, a circuit for generating a reference voltage and a circuit for generating a voltage drop value for monitoring overcurrent are provided. It is possible to improve the identity of the overcurrent, and more accurate overcurrent determination can be performed.

[0018]

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

[Embodiment 1] FIG. 1 shows the configuration of a semiconductor device with an overcurrent prevention function according to the present embodiment. The device of this example is a semiconductor device in which the output power MOSFET 206 is driven by the gate drive circuit 205, similar to the conventional device described above. The output current flowing through the output power MOSFET 206 is M for current monitoring, which is also driven by the gate drive circuit 205.
It is monitored by the OSFET 207. M for this monitor
The OSFET 207 is formed by the same manufacturing method as the power MOSFET 206, and has the same structure.
However, the on resistance of the power MOSFET 206 is 50
It is very low, about mΩ, and drives a current of about 10 A. On the other hand, the monitoring MOSFET 207 has a channel width reduced and has an ON resistance of several ten thousand to several hundred thousand times. Therefore, a minute current is caused to flow by using this monitor MOSFET 207, and the current flowing through the power MOSFET 206 is judged from the voltage drop of the monitor resistor 204 connected in series with the monitor MOSFET 207, and the overcurrent can be detected. ing.

The apparatus of this embodiment uses the differential operational amplifier 2 in order to determine the voltage drop in the monitor resistor 204.
02 is used. That is, the connection point N21 between the monitor MOSFET 207 and the monitor resistor 204 connected in series is connected to the non-inverting input N25 of the operational amplifier 202 via the resistor R24, while the operational amplifier 202 is connected.
The reference voltage from the reference voltage generation circuit 201 is applied to the inverting input N23. Then, the operational amplifier 202
Output N24 is connected to the gate electrode of the current limiting MOSFET 203. This current limiting MOSFET
Reference numeral 203 denotes a gate drive circuit 105 to a power MOSFET, similarly to the conventional current limiting MOSFET 109.
206 is connected to a signal line having a connection point N22 branching to the respective gate electrodes of 206 and the monitor MOSFET 207. When the gate potential of the current limiting MOSFET 203 becomes high, the potential of the signal line having this connection point N22 decreases. Is becoming Therefore, the power MOS which is the main path
As the current flowing through the FET 206 increases, the MO for monitoring
The potential of the connection point N21 rises via the SFET 207,
When the reference potential of the connection point N23 is exceeded, the potential of the output N24 of the operational amplifier 202 is inverted. Therefore, the operational amplifier 2
02, the impedance of the current limiting MOSFET 203, whose gate electrode is connected to the output N24, is lowered, and the potential of the signal line N22 is lowered. Therefore, the power MO
The SFET 206 enters the current limiting operation, and the monitor MOS
The current flowing through the FET 207 is also reduced. Therefore, the potential of the connection point N21 also decreases, and the current flowing through the power MOSFET 206 is stabilized at the place where the connection point N25 input to the operational amplifier 202 and the reference potential N23 become equal in potential, and an overcurrent can be prevented.

In the device of this example, the connection point N2 of the gate drive circuit 205 to the current limiting MOSFET 203 is connected.
A resistor R21 inserted between 6 and a resistor R22 inserted between the connection points N26 and N22, a resistor R23 inserted between the connection points N22 and N25, and a connection point N2.
The resistances R24 inserted between 5 and the connection point N21 are about 3 kΩ, 2 kΩ, 500 kΩ, and 1 kΩ, respectively. The resistance value Rse2 of the monitor resistor 204 is 4
It is about 00Ω. Therefore, the connection point N21 and the connection point N
The potential of the operational amplifier 22 is almost equal to that of the connection point N2 of the operational amplifier 22.
5, the voltage drop value at the resistance value Rse2 is input. This monitor resistor 204 uses a resistor formed by diffusion on a semiconductor device, and its resistance value Rse2 exhibits a negative temperature dependency of about 2000 ppm / ° C. Therefore, in the apparatus of this example, a reference voltage generating circuit having a temperature compensation function is used for the reference voltage generating circuit 201 so that a constant overcurrent can be determined in the entire operating temperature range of the apparatus of this example. .. That is, since the resistance value Rse2 of the monitor resistor 204 changes with temperature, even if a constant overcurrent flows through the resistor 204, the voltage drop value changes with temperature in proportion to the resistance value Rse2. Therefore, if the reference voltage to be compared with this voltage drop value in the operational amplifier 202 is constant irrespective of temperature, the determination result of overcurrent fluctuates depending on temperature, excessive current flows, or the ability of the main path is exerted. Problems such as not being possible occur. To prevent such problems,
A reference voltage having the same temperature dependency as the voltage drop value in the monitor resistor 204 may be applied to the operational amplifier 202. Therefore, the apparatus of this example employs the reference voltage generation circuit 201 with a temperature compensation function that can generate the reference voltage having such temperature dependence.

FIG. 2 shows the configuration of the reference voltage generating circuit 201 with a temperature compensation function of this example.

The reference voltage generating circuit 201 of the present example has a constant voltage generating section 10 for generating a constant voltage, a constant voltage lowering section 20 for generating a constant voltage drop, a constant voltage generating section 10 and a constant voltage lowering section 20. Is composed of a specific resistance portion 30 whose contribution to the reference voltage can be adjusted. Constant voltage generator 1 of this example
0 is a Zener diode 302 whose anode side is grounded
Is used, and the cathode side N31 is connected to the power supply potential Vcc via the depletion type current adjusting MOSFET 301. This current adjustment MOSFE
The gate electrode of T301 is connected to the cathode side N31 of the Zener diode 302, and
The constant voltage controlled by 02 is applied, and it is adjusted so that a predetermined current flows. This is because the constant voltage generated by the Zener diode 302 has some current dependency, so that a predetermined current is made to flow through the Zener diode 302 by using the current adjusting MOSFET 301 to generate an accurate constant voltage. is there.

The constant voltage drop unit 20 of the apparatus of this example is
It is composed of two diodes 304 and 305 and an NPN transistor 303 which are connected in series with the specific resistance portion 30 interposed therebetween. The base of the NPN transistor 303 is connected to the cathode side N31 of the Zener diode 302, and the emitter side is the anode side N31 of the diode 304.
Connected to 32. The power supply potential Vcc is applied to the collector side. The cathode side N33 of the diode 304 is connected to the other diode 3 via the resistors 306 and 307 which are connected in series and which form the specific resistance section 30.
05 is connected to the anode side N35, and the cathode side of this diode 305 is grounded. And
The potential at the connection point N34 with the resistance 306 having the resistance value R1 and the resistance 307 having the resistance value R2 that form the specific resistance unit 30 is supplied to the connection point N23 with the operational amplifier 202 as the reference potential Vref0.

The reference potential Vref0 generated by such a circuit configuration is expressed by the following equation.

[0026]

[Equation 1]

Here, Vz is the Zener diode 302
, Vf indicates the forward voltage at the PN junction of the diodes 304 and 305 and the transistor 303.

Here, in order to show the temperature dependence of the equation (1), differentiation with the temperature T is as follows.

[0029]

[Equation 2]

Here, the temperature dependences of the Zener voltage Vz and the forward voltage Vf are as follows.

[0031]

[Equation 3]

That is, the Zener voltage Vz shows a positive temperature dependence, and the forward voltage Vf shows a negative temperature dependence. Therefore, as shown in equation (2), the temperature dependence of the reference voltage Vref0 can be freely controlled by changing the ratio of the resistance values R1 and R2. Also, Vre
The value of f0 itself is, as shown in the equation (1), the Zener voltage V
It can be freely adjusted by z. Therefore, by adjusting the ratio of the resistance values R1 and R2, it is possible to make the reference voltage Vref0 have the same temperature dependency as the monitor resistor 204.

As described above, the reference voltage generating circuit 20 of the present example.
1 includes a constant voltage generator 10 having a positive temperature dependency and a constant voltage drop unit 20 having a negative temperature dependency which is an inverse temperature dependency, and a reference voltage Vr having these temperature dependencies.
The influence on ef0 can be adjusted by the specific resistance unit 30, and the reference voltage having the temperature dependency similar to that of the monitoring resistor 204 can be generated. Therefore, by comparing the reference voltage from the reference voltage generating circuit of this example with the voltage drop value from the monitor resistor, it is possible to accurately determine the overcurrent in the entire operating temperature range of the device. Therefore, in the device of this example, it is possible to prevent the main path from being destroyed due to overcurrent in the entire temperature range, and to make the power MOSFET, which is a switching element, exhibit a predetermined function.

[Second Embodiment] FIG. 3 shows a reference voltage generating circuit 201 of a semiconductor device with an overcurrent preventing function according to the present embodiment. Except for the reference voltage generation circuit 201, it is the same as in the first embodiment, and illustration and description thereof will be omitted.

In the reference voltage generating circuit 201 of this example, the drain is connected to the power supply potential Vcc, and a predetermined reference current Ire is supplied.
A reference voltage generating circuit including a reference current generating MOSFET 408 for flowing f and a reference resistor 409 having a resistance value Rref connected in series with the reference current controlling MOSFET 408.
The voltage drop value at 9 is supplied to the connection point N23 of the operational amplifier 202 as the reference voltage Vref1. In such a reference voltage generation circuit 201, the reference current Iref by the reference current control MOSFET 408 has temperature dependence. Therefore, the reference voltage generation circuit 20 of the present example
In No. 1, in order to eliminate the temperature dependence from Iref, the control potential from the temperature compensation control unit 40 having the temperature compensation function is applied to the gate electrode of the reference current control MOSFET 408. The configuration of the temperature compensation control unit 40 can be realized with the same configuration as the reference voltage generation circuit of the first embodiment. That is, the reference current control MOSFET 408
The ON resistance of 1 has a positive temperature dependency, and the following relationship is established between the control voltage Vref0 applied to the gate electrode and the reference current Iref.

[0036]

[Equation 4]

Here, Gm is the transconductance of the MOSFET 408. Therefore, the temperature compensation control unit 40
If the resistance values R1 and R2 of the specific resistance part 30 that controls the control voltage Vref0 are determined so as to satisfy the equations (1), (2) and (4), the control voltage Vref0
Thus, the reference current Iref having no temperature dependence can be passed from the current control MOSFET 408. Then, a constant reference current Ir is maintained over the entire operating temperature range of the device of this example.
ef can be supplied to the reference resistor 409, and by using a resistor having the same temperature dependency as the monitor resistor 204 as the resistance value Rref of the reference resistor 409, it is possible to determine a constant overcurrent over the entire operating temperature range. Reference voltage Vref1
Can be supplied.

Further, in the reference voltage generating circuit 201 of this example, the structure from the current control MOSFET 408 to the reference resistor 409 is the monitoring MOS of the semiconductor device.
The configurations of the FET 207 and the monitor resistor 204 are the same. Therefore, it is easy to form them on the same semiconductor substrate by the same process as the monitor resistor 204, and it becomes possible to make the respective resistance values Rref and Rse2 have the same value and the same temperature dependency. Therefore, it is possible to eliminate manufacturing variations that occur in the resistance values Rref and Rse2, and by comparing the reference voltage Vref1 from the reference voltage generation circuit 201 of this example with the voltage of the connection point N21, the reference current Iref is obtained. And the current related to the overcurrent flowing through the monitor MOSFET 207 can be accurately compared. As described above, in the device of this example, the current value can be determined more accurately,
The ability of the power MOSFET 206 can be fully exerted while preventing overcurrent.

The configuration of the temperature compensation control unit 40 of this example is the same as that of the reference voltage generating circuit described in the first embodiment, and therefore the same reference numerals are given and the description thereof is omitted.

[Embodiment 3] FIG. 4 shows a reference voltage generating circuit 201 of a semiconductor device with an overcurrent preventing function according to this embodiment. Except for the reference voltage generation circuit 201, it is the same as in the first embodiment, and illustration and description thereof will be omitted.

The reference voltage generating circuit 201 of this example has substantially the same structure as the reference voltage generating circuit 201 described in the second embodiment, and the common portions are denoted by the same reference numerals and the description thereof will be omitted. A point to be noted in the reference voltage generation circuit 201 of this example is that the reference current control MOSFET 4 is used.
That is, the drain of 08 is connected to the load terminal P1 of the power MOSFET 206 similarly to the monitor MOSFET 207. Therefore, the reference voltage generation circuit 2 of this example
In 01, the reference voltage generation unit 50 applied from the reference current control MOSFET 408 to the reference resistor 409 can be manufactured with the same configuration as the monitor MOSFET 207 and the monitor resistor 204. Therefore, the reference voltage generation unit 50 can be formed on the same semiconductor substrate in the same process as the monitor MOSFET 207 and the monitor resistor 204, and the manufacturing variation is excluded,
It is possible to realize the reference current control MOSFET 408 having the same current characteristic as the monitor MOSFET 207 and the reference resistor 409 having the same resistance characteristic as the monitor resistor 204. Therefore, the reference current control MO
The SFET 408 controls the control voltage V from the temperature compensation control unit 40.
Monitor MOSFET by controlling with ref0
It is possible to compare the limiting current value of the overcurrent and the current value actually flowing in the main circuit by eliminating the manufacturing variation generated in 207 and the reference resistor 204 or the influence of the temperature change. As a result, the semiconductor device can be protected from overcurrent, and at the same time, the capability of the power MOSFET can be fully exhibited.

In the second and third embodiments, the reference current controlling MOFSET 408 is operated in the saturation region in order to eliminate the influence from the fluctuation of the power supply voltage or the fluctuation of the output voltage of the power MOSFET. Further, the reference voltage generating circuit having the temperature compensation function of the present example has a power M
The present invention can be applied not only to IPS having OSFET and the like, but also to an output overcurrent protection circuit in a general IC.

[0043]

As described above, in the reference voltage generator and the semiconductor device with the overcurrent prevention function according to the present invention, the reference voltage of the reference voltage is changed by changing the resistance ratio of the specific resistance means of the reference voltage generator. The temperature characteristics can be controlled. Therefore, in the entire operating temperature range of the device, the monitor MIS
By compensating for the temperature dependence of the FET and the monitor resistance means, it becomes possible to limit the current to a constant value. Therefore, it is possible to realize a semiconductor device capable of completely preventing damage due to overcurrent and capable of sufficiently exhibiting the performance of a switching element or the like.

Further, the monitor MISFET and the monitor resistance means, and the reference current control MISFET and the reference resistance means can be incorporated in the semiconductor device by the same process, and the reference voltage generating section is realized by the elements having the same structure. it can. Therefore, it is possible to suppress the difference in temperature characteristics between the overcurrent detection side and the reference voltage generation side, and it is also possible to prevent variations due to the manufacturing process. Therefore, in the semiconductor device with an overcurrent prevention function according to the present invention, it is possible to perform stable and accurate comparison with the limiting current value for preventing overcurrent, a highly reliable, high-performance semiconductor device. The device can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a semiconductor device with an overcurrent prevention function.

FIG. 2 is a circuit diagram showing a configuration of a reference voltage generation circuit according to the first embodiment.

FIG. 3 is a circuit diagram showing a configuration of a reference voltage generation circuit according to a second embodiment.

FIG. 4 is a circuit diagram showing a configuration of a reference voltage generation circuit according to a third embodiment.

FIG. 5 is a block diagram showing a configuration of a conventional semiconductor device with an overcurrent prevention function.

[Explanation of symbols]

 10 ... Constant voltage generation unit 20 ... Constant voltage drop unit 30 ... Specific resistance unit 40 ... Temperature compensation control unit 50 ... Reference voltage generation unit 101, 206 ... Power MOSFET 102, 207 ... Monitoring MOSFETs 103, 204 ... Monitoring resistors 104, 208 ... Regulators 105, 205 ... Gate drive circuits 106 ... Inverters 107, 108 ... MOSFETs 109, 203 ... Currents Limiting MOSFET 301 ... Current adjusting MOSFET 302 ... Zener diode 303 ... NPN transistor 304, 305 ... Diode 306, 307 ... Resistor 408 ... Reference current adjusting MOSFET 409 ... Reference resistance

Claims (7)

[Claims] 1. At least one constant voltage drop means connected in series to the constant voltage generation means and two or more resistance means, and a voltage value divided by these resistance means can be referred to as a reference voltage. In a reference voltage generator having a reference voltage generator, the constant voltage generator is a temperature-dependent constant voltage generator whose temperature dependence of the generated voltage is monotonous.
The constant voltage drop means is a temperature dependent type constant voltage drop means in which the temperature dependence of the drop voltage is opposite to that of the constant voltage generation means and is monotonic, and the resistance means is a ratio of resistance values of these two or more resistance means. A reference voltage generator characterized in that it is a specific resistance means capable of setting. 2. The temperature-dependent constant voltage generating means according to claim 1, comprising a load element connected to a power supply potential and having a constant current function, and a zener diode connected in series with the load element. A reference voltage generator characterized in that the anode of the Zener diode is connected to the ground potential. 3. The temperature dependent constant voltage drop means according to claim 1 or 2, wherein at least one of a base-emitter voltage drop of a bipolar transistor and a diode forward voltage drop is used. A reference voltage generator. 4. A reference voltage generator having a reference current control MISFET for generating a reference current having a predetermined current value, and reference resistance means capable of referring to a voltage drop due to this reference current as a reference voltage. A reference voltage generating device according to any one of claims 1 to 3, wherein a reference voltage is applied to the gate potential of the reference current controlling MISFET. 5. A monitor MISFET for detecting an overcurrent passing through a switching element, and this monitor MISF.
What is claimed is: 1. A semiconductor device with an overcurrent prevention function, comprising: a monitor resistance means connected in series with ET; and a judgment means for comparing a voltage drop value in the monitor resistance means with a reference voltage to detect an overcurrent. 5. A semiconductor device with an overcurrent prevention function, comprising the reference voltage generator according to claim 1, wherein the reference voltage of the reference voltage generator is used as the reference voltage. 6. A monitor MISFET for detecting an overcurrent passing through a switching element, and this monitor MISF.
What is claimed is: 1. A semiconductor device with an overcurrent prevention function, comprising: a monitor resistance means connected in series with ET; and a judgment means for comparing a voltage drop value in the monitor resistance means with a reference voltage to detect an overcurrent. 5. The reference voltage generator according to claim 4, wherein the reference voltage of the reference voltage generator is used as the reference voltage, and the reference current control MISFE is used.
T is the same process MISFET formed on the semiconductor substrate by the same process as the monitor MISFET, and the reference resistance means is the same process resistance means formed on the semiconductor substrate by the same process as the monitor resistance means. A semiconductor device with an overcurrent prevention function, characterized in that 7. The semiconductor device with an overcurrent prevention function according to claim 6, wherein the reference current control MISFET and the monitor MISFET are connected in parallel.