JP4356811B2 - Semiconductor device with thermal shutdown circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device including a thermal shutdown circuit that detects a temperature and stops a device function at a predetermined temperature range or higher.
Such a semiconductor device is used for a power supply IC (integrated circuit), for example.
[0002]
[Prior art]
Generally, a semiconductor device with a high operating voltage and a large operating current is equipped with a thermal shutdown circuit for protecting the device because the semiconductor device itself may be destroyed due to a high temperature during operation. It is often done.
[0003]
The thermal shutdown circuit stops the operation of each circuit of the semiconductor device when the temperature exceeds a certain set temperature (for example, 130 ° C.) due to heat generated during the operation of the semiconductor device itself, and notifies the output terminal that a temperature abnormality has occurred. A signal is output.
One prior art of such a thermal shutdown circuit uses the temperature characteristics of the forward current of a PN junction (see, for example, Patent Document 1 and Patent Document 2).
[0004]
FIG. 5 shows a cross-sectional view of an NPN bipolar transistor as an example of a temperature detection element.
An N well region (N-well) 35 is formed on the surface side of the P-type semiconductor substrate (P-sub) 33. In the N well region 35, a P-type region (P−) constituting a base 37 of the NPN bipolar transistor is formed. In the P-type region base 37, an N-type region (N +) constituting an emitter 39 of an NPN bipolar transistor is formed. In the N well region 35, an N-type region (collector) 43 of an NPN bipolar transistor, which is electrically isolated from the base 37 by a LOCOS (local oxidation of silicon) oxide film 41 for element isolation, is formed. N +) is formed.
[0005]
When the base 37 and the collector 43 of the NPN bipolar transistor are electrically connected and a constant current of several μA (microampere), for example, 1 μA, is supplied to the emitter 7, the base-emitter voltage V _BE is about 0.7-0. It becomes .9V (volt).
The base-emitter voltage V _BE varies linearly with temperature, and the rate of change is constant at about -2 mV (millivolt) / ° C. Using this temperature characteristic, the base-emitter voltage V _BE and a predetermined reference voltage are compared by a comparator circuit, and when the voltage drops below the predetermined reference voltage, a signal for stopping the entire circuit is issued, thereby giving a predetermined temperature. Thus, a thermal shutdown function for stopping the circuit function can be realized.
[0006]
[Patent Document 1]
JP-A-9-246876 [Patent Document 2]
Japanese Patent Laid-Open No. 10-201080
[Problems to be solved by the invention]
For example, in a power supply IC used as a part of a portable device such as a battery drive, current consumption during standby is a big problem from the viewpoint of reducing the battery life and the number of times of charging.
However, since the thermal shutdown circuit as described above is configured to monitor the temperature while continuously supplying a current of several μA even when the IC is in a standby state, it contributes to an increase in current consumption during standby. It has become.
[0008]
Therefore, an object of the present invention is to reduce current consumption in a semiconductor device having a thermal shutdown circuit at least in an operation guarantee temperature region.
[0009]
[Means for Solving the Problems]
The semiconductor device of the present invention is provided with a thermal shutdown circuit that detects the temperature and stops the device function at a predetermined temperature range or higher, and has a switch MOS in the wiring for supplying power to the thermal shutdown circuit. A transistor is provided.
[0010]
In the temperature guaranteed temperature range of the semiconductor device, the switch MOS transistor is turned off to cut off the power supply to the thermal shutdown circuit. In the high temperature range where the device function is desired to be stopped, the switch MOS transistor is turned on. By operating the thermal shutdown circuit, the current consumption in the guaranteed operating temperature range can be reduced.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In the semiconductor device of the present invention, the threshold voltage of the switch MOS transistor is such that no channel current flows in the operation guaranteed temperature region of the semiconductor device, and the thermal shutdown circuit is set in the high temperature region where the device function is desired to be stopped. It is preferably set to a value that generates a leak current that can be operated.
Thereby, the operation of the thermal shutdown circuit can be automatically switched to the on state or the off state.
[0012]
The switching MOS transistor is composed of an N channel MOS transistor (hereinafter referred to as an Nch MOS transistor) having a gate potential set to a ground potential, or a P channel MOS transistor (hereinafter referred to as a Pch MOS transistor) having a gate potential fixed to a power supply potential. An example can be given.
[0013]
As an example of a semiconductor device to which the present invention is applied, in addition to the thermal shutdown circuit, a dividing resistor for dividing an input voltage and supplying a divided voltage, a reference voltage generating circuit for supplying a reference voltage, and the dividing resistor A voltage detection circuit having a comparison circuit for comparing the divided voltage from the reference voltage and the reference voltage from the reference voltage generation circuit, or an output driver for controlling the output of the input voltage, and dividing the output voltage to obtain the divided voltage. The divided resistor for supplying, the reference voltage generating circuit for supplying the reference voltage, the divided voltage from the divided resistor, and the reference voltage from the reference voltage generating circuit are compared, and the output driver of the output driver is compared according to the comparison result. A power supply IC further including a constant voltage generation circuit including a comparison circuit for controlling the operation, or both can be given.
According to the present invention, the operation of the thermal shutdown circuit in the operation guarantee temperature region can be stopped, so that the current consumption in the operation guarantee temperature region can be reduced for the power supply IC to which the present invention is applied.
[0014]
【Example】
FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to a power supply IC.
A thermal shutdown circuit 1, a constant voltage generation circuit 3, a voltage detection circuit 5, and a logic circuit 7 are provided. Each circuit 1, 3, 5, 7 is connected to a power supply wiring 11 connected to a DC power supply (Vcc) 9 and a GND wiring 15 connected to a GND (ground potential) 13. A switching NchMOS transistor 17 is provided between the thermal shutdown circuit 1 and the power supply wiring 11. The gate electrode of the switching NchMOS transistor 17 is connected to the GND wiring 15.
[0015]
FIG. 2 is a circuit diagram showing an example of the constant voltage generation circuit 3.
The constant voltage generation circuit 3 includes an input terminal 19 connected to a DC power supply 9 through a power supply line 11, a reference voltage generation circuit (Vref) 21 as a reference voltage source, an operational amplifier 23, and a PchMOS transistor 25 constituting an output driver. , Division resistors R1, R2 and an output terminal (Vout) 27 are provided.
[0016]
The operational amplifier 23 of the constant voltage generation circuit 17 has an output terminal connected to the gate electrode of the Pch MOS transistor 25, the reference voltage Vref from the reference voltage generation circuit 21 applied to the inverting input terminal, and the output voltage Vout applied to the non-inverting input terminal. A voltage divided by the dividing resistors R1 and R2 is applied, and the divided voltage from the dividing resistors R1 and R2 is controlled to be equal to the reference voltage Vref.
[0017]
FIG. 3 is a circuit diagram showing an example of the voltage detection circuit 5.
In the voltage detection circuit 5, reference numeral 23 denotes an operational amplifier. A reference voltage generation circuit 21 is connected to an inverting input terminal of the operational amplifier 23 and a reference voltage Vref is applied. The voltage of the terminal to be measured input from the input terminal 29, here the voltage of the DC power supply 9 connected via the power supply wiring 11, is divided by the dividing resistors R1 and R2 and input to the non-inverting input terminal of the operational amplifier 23. Is done. The output of the operational amplifier 23 is output to the outside through an output terminal (Vout) 31.
[0018]
In the voltage detection circuit 5, when the voltage of the terminal to be measured is high and the voltage divided by the dividing resistors R1 and R2 is higher than the reference voltage Vref, the output of the operational amplifier 23 maintains the H level, and the DC power source 9 When the voltage drops and the voltage divided by the dividing resistors R1 and R2 becomes lower than the reference voltage Vref, the output of the operational amplifier 23 becomes L level.
[0019]
Returning to FIG. 1, the description will be continued.
The threshold voltage of the switching NchMOS transistor 17 is set to, for example, 0.50 V at 25 ° C. by adjusting the impurity concentration of the transistor channel portion in a normal semiconductor manufacturing process.
The thermal shutdown circuit 1 is designed to operate with a current of 1 μA or more, for example.
[0020]
When the threshold voltage of the switching NchMOS transistor 17 is set to 0.50 V, the off-leakage current when the gate voltage is set to GND and the drain voltage is set to the power supply voltage is an operation guaranteed temperature range of a normal semiconductor device (for example, −45 ~ 85 ° C), it is 100 pA (picoampere) or less. For example, when the gate length is 3 μm, the transistor width is 1000 μm, the temperature is 85 ° C., the gate voltage Vg is GND, and the drain voltage Vd is 5 V, the off-leakage current is about 50 pA.
[0021]
In the normal operation guaranteed temperature range of the semiconductor device, the switch NchMOS transistor 17 connected between the power supply line 11 and the thermal shutdown circuit 1 is in an off state, and the thermal shutdown circuit 1 operates with a current of, for example, 1 μA or more. Since it is designed, it does not operate even if a leakage current of about 50 pA is supplied from the switching NchMOS transistor 17.
[0022]
Therefore, since no current flows through the thermal shutdown circuit 1 in the normal operation guaranteed temperature range of the semiconductor device, it does not contribute to the standby current of the entire circuit and has a lower standby than the conventional semiconductor device equipped with the thermal shutdown circuit. Current can be realized. In other words, the thermal shutdown circuit can be mounted without increasing the standby current.
[0023]
Further, the threshold voltage of the switching NchMOS transistor 17 decreases with a coefficient of about −2 mV / ° C. as the temperature rises. Further, a power supply voltage is applied to the impurity region constituting the drain, and reverse junction leakage occurs between the impurity region and the substrate. This junction leakage also increases as the temperature rises. When the semiconductor device becomes high temperature due to self-heating or the like and approaches a high temperature region where the device itself may be destroyed, the leakage current of the switching NchMOS transistor 17 decreases the threshold voltage and increases the reverse junction leakage. For example, at 130 ° C., the leakage current reaches about several μA.
[0024]
When the leakage current of the switching NchMOS transistor 17 becomes 1 μA or more, the thermal shutdown circuit 1 starts to operate, and the thermal shutdown circuit 1 monitors the temperature-detecting element, for example, the base-emitter voltage V _BE of the NPN transistor shown in FIG. To do. When the base-emitter voltage V _BE corresponding to a predetermined temperature, for example, 150 ° C. is detected, the circuit functions of the constant voltage generation circuit 3, the voltage detection circuit 5, and the logic circuit 7 are stopped, and a temperature abnormality signal is generated. Output.
[0025]
As described above, the switch NchMOS transistor 17 stops the power supply in the guaranteed operating temperature range of the semiconductor device to stop the operation of the thermal shutdown circuit 1, and supplies the power supply in a predetermined high temperature region to supply the thermal shutdown circuit 1. By operating the, it is possible to reduce the current consumption within the guaranteed operating temperature range while preventing the semiconductor device from being destroyed due to the temperature rise due to self-heating.
[0026]
Further, by changing the threshold voltage at 25 ° C. of the switching NchMOS transistor 17, the operation start temperature of the thermal shutdown circuit can be set to an arbitrary value.
[0027]
FIG. 4 shows 110 ° C., 130 ° C. and 150 ° C. when the threshold voltage of the NchMOS transistor is changed and the transistor width is set so that the leakage current at 90 ° C. is 100 nA. The actual measurement data which showed the fluctuation | variation of the leakage current of are shown. An NchMOS transistor having a channel length of 7 μm and a channel width of 600 μm was used, and measurement was performed under conditions of a gate voltage of 0 V and a drain voltage of 50 V.
[0028]
As can be seen from FIG. 4, as the threshold voltage setting at 25 ° C. increases, the leakage current in the high temperature region increases. Based on the data of FIG. 4, when the thermal shutdown circuit is designed to operate at 1 μA, for example, the threshold voltage at 25 ° C. of the switching NchMOS transistor 17 is set to about 0.7V. The shutdown circuit can be operated from around 130 ° C.
[0029]
Further, by changing the threshold voltage setting at 25 ° C. to about 0.5 V, the thermal shutdown circuit does not operate near 130 ° C., but can operate from around 150 ° C.
It is also possible to freely change the operation start temperature by changing the design of the current value at which the thermal shutdown circuit starts to operate while keeping the threshold voltage at 25 ° C. of the switching NchMOS transistor 17 constant. It is.
[0030]
In the above embodiment, an Nch MOS transistor is used as the switch MOS transistor connected between the power supply and the thermal shutdown circuit. However, the present invention is not limited to this, and a Pch MOS transistor is used as the switch MOS transistor. You can also. In that case, the gate electrode is fixed at the power supply voltage potential.
[0031]
As mentioned above, although the Example of this invention was described, this invention is not limited to these, A various change is possible within the range of this invention described in the claim.
[0032]
【The invention's effect】
In the semiconductor device according to claim 1, in the semiconductor device provided with the thermal shutdown circuit, the switching MOS transistor is provided in the wiring for supplying power to the thermal shutdown circuit. In the guaranteed temperature range, the switch MOS transistor is turned off to cut off the power supply to the thermal shutdown circuit, and in the high temperature range where the device function is desired to be stopped, the switch MOS transistor is turned on to activate the thermal shutdown circuit. By operating, current consumption in the guaranteed operating temperature range can be reduced.
[0033]
Further, in the semiconductor device according to claim 1 , the threshold voltage of the switching MOS transistor does not flow a channel current in the operation guaranteed temperature region of the semiconductor device, and in a high temperature region where the device function is desired to be stopped. Since the leak current that can operate the thermal shutdown circuit is set to a value that can be operated, the operation of the thermal shutdown circuit can be automatically switched to the on state or the off state.
[0034]
In the semiconductor device according to claim 2 , since the semiconductor device of the present invention is applied to the power supply IC further including the voltage detection circuit and / or the constant voltage generation circuit in addition to the thermal shutdown circuit, The operation of the thermal shutdown circuit in the guaranteed temperature region can be stopped, and current consumption in the guaranteed operation temperature region can be reduced for the power supply IC.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment applied to a power supply IC.
FIG. 2 is a circuit diagram showing an example of a constant voltage generation circuit that constitutes a part of the embodiment;
FIG. 3 is a circuit diagram showing an example of a voltage detection circuit constituting a part of the same embodiment;
FIG. 4 is data showing the relationship between a threshold voltage at 25 ° C. and an off-leakage current (Ioff) in a high temperature region for an Nch MOS transistor, the horizontal axis is the threshold voltage (V), and the vertical axis is the off-leakage. Current (A) is shown.
FIG. 5 is a cross-sectional view showing an NPN bipolar transistor as an example of a temperature detection element of a thermal shutdown circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Thermal shutdown circuit 3 Constant voltage generation circuit 5 Voltage detection circuit 7 Logic circuit 9 DC power supply 11 Power supply wiring 13 GND (ground potential)
15 GND wiring 17 Switch NchMOS transistor 19 Input terminal 21 Reference voltage generation circuit 23 Operational amplifier 25 PchMOS transistor 27 for output driver Output terminal 29 Input terminal 31 Output terminals R1, R2 Dividing resistors

Claims (2)

In a semiconductor device with a thermal shutdown circuit that detects the temperature and stops the device function above a predetermined temperature range,
A wiring for supplying power to the thermal shutdown circuit includes a switching MOS transistor ,
The threshold voltage of the switching MOS transistor is a leakage current that does not cause a channel current to flow in the operation guarantee temperature region of the semiconductor device and can operate the thermal shutdown circuit in a high temperature region where the device function is desired to be stopped. Is set to a value that generates
2. The semiconductor device according to claim 1, wherein the switching MOS transistor comprises an N channel MOS transistor having a gate potential set to a ground potential or a P channel MOS transistor having a gate potential fixed to a power supply potential . In addition to the thermal shutdown circuit, a divided resistor for dividing the input voltage and supplying a divided voltage, a reference voltage generating circuit for supplying a reference voltage, a divided voltage from the divided resistor, and the reference voltage generating circuit Detection circuit having a comparison circuit for comparing the reference voltages of the output voltage, an output driver for controlling the output of the input voltage, a dividing resistor for dividing the output voltage and supplying the divided voltage, and supplying a reference voltage A reference voltage generating circuit for comparing the divided voltage from the dividing resistor and the reference voltage from the reference voltage generating circuit, and a comparison circuit for controlling the operation of the output driver according to the comparison result. The semiconductor device according to claim 1 , further comprising a voltage generation circuit, or both.

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