JP2004253936A - Semiconductor integrated circuit with thermal protective function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more accurately prevent a power transistor from being overheated by placing a temperature detection transistor immune to the effect of a parasitic transistor in the vicinity of the power transistor for driving an inductive load or the like. <P>SOLUTION: The temperature detection NPN (n-semiconductor/p-semiconductor/n-semiconductor) bipolar transistor whose collector and base are connected to the point of a power supply potential Vcc and whose emitter is connected to the point of a second power supply potential Vgnd via a current passing means Isa is arranged close to the power transistor QA, and the emitter potential Vsa of the temperature detection transistor Qsa is compared with a reference potential Vref and a thermal protection signal Stsd is outputted. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor integrated circuit (hereinafter, IC) having a thermal protection function, including a power transistor for driving a load such as a motor or a coil, and a thermal protection circuit for protecting the power transistor from an abnormal temperature rise. .
[0002]
[Prior art]
Conventionally, a thermal protection circuit for protecting a power transistor for driving a load from an abnormal temperature rise due to an overload or the like has been provided in an IC.
[0003]
FIG. 10 is a diagram showing a configuration of such a conventional thermal protection circuit (see Patent Document 1). In FIG. 10, an NPN bipolar transistor for temperature detection (hereinafter, temperature detection transistor) Qsa is arranged near a power NPN bipolar transistor (hereinafter, power transistor) QA so as to be thermally coupled. I have. The emitter of the temperature detection transistor Qsa is connected to the ground potential Vgnd, and its base is supplied with the reference potential Vref. The collector of the temperature detection transistor Qsa is connected to the thermal shutdown detection circuit D-TSD. The reference potential Vref is set to a value suitable for the temperature detection operation by dividing a constant voltage obtained from the constant voltage power supply CV2 by the resistors R1 and R2.
[0004]
The base-emitter voltage Vbe of the temperature detection transistor Qsa has a negative temperature characteristic of about −2 mV / ° C. Since the temperature detection transistor Qsa is thermally coupled to the power transistor QA, the temperature of the temperature detection transistor Qsa increases as the temperature of the power transistor QA increases, and the base-emitter voltage Vbe decreases.
[0005]
When the junction temperature Tj at the junction of the power transistor QA reaches a predetermined temperature to be protected (for example, 175 ° C.), the thermal shutdown detection circuit D-TSD detects the operating state (collector potential Vqsa) of the temperature detection transistor Qsa. Then, a thermal shutdown signal Stsd is generated.
[0006]
The drive signal to the power transistor QA is turned off by this thermal shutdown signal Stsd to protect it from thermal destruction.
[0007]
[Patent Document 1]
Japanese Patent Publication No. 6-16540
[Problems to be solved by the invention]
However, when the load driven by the power transistor QA is an inductance load such as a motor or a coil as shown in FIG. 11, a malfunction occurs in the temperature detection operation. This malfunction will be described below.
[0009]
In FIG. 11, power transistors QA to QD are NPN bipolar transistors for power, DA and DB are flywheel diodes, and control the speed of the motor M in the forward or reverse direction.
[0010]
During normal rotation, the power transistors QC and QB are selected, the power transistor QC is turned on / off by, for example, PWM control, and the power transistor QB is turned on. Power transistors QD and QA remain off. When the power transistor QC is on, a current flows from the power supply potential Vcc to QC → M → QB → ground potential Vgnd. When the power transistor QC is off, a current flows from M → QB → ground potential Vgnd → diode DA. When the power transistor QC is off, the collector potential Vqa of the power transistor QA becomes a negative potential lower than the ground potential Vgnd.
[0011]
Since a P-type isolation region connected to the ground potential is formed between the power transistor QA and the temperature detection transistor Qsa, the collector of the power transistor QA, the P-type isolation region, and the collector of the temperature detection transistor Qsa A parasitic lateral NPN bipolar transistor (hereinafter referred to as a parasitic transistor) Qps is formed therebetween.
[0012]
Therefore, when the collector potential Vqa of the power transistor QA becomes a negative potential, the parasitic transistor Qps conducts, and the collector potential Vqsa decreases regardless of the operation of the temperature detection transistor Qsa. As a result, the thermal shutdown detection circuit D-TSD operates, and the thermal shutdown signal Stsd is erroneously generated.
[0013]
Such a malfunction can be avoided by disposing the temperature detection transistor Qsa at a long distance from the power transistor QA as a heat source. However, by increasing the distance, the sensitivity of the temperature detection decreases, and it becomes difficult to accurately detect the temperature of the power transistor QA for which overheating protection is desired.
[0014]
Therefore, the present invention provides an IC capable of more accurately protecting a power transistor from overheating by arranging a temperature detection transistor which is not affected by a parasitic transistor near a power transistor for driving a load such as a motor or a coil. The purpose is to provide.
[0015]
In addition, ICs that individually arrange temperature detecting transistors that are not affected by parasitic transistors in close proximity to a plurality of power transistors and that can more accurately protect each power transistor from overheating without increasing the chip size. The purpose is to provide.
[0016]
[Means for Solving the Problems]
In the IC with a thermal protection function according to the first aspect, the collector is connected to the first power supply potential Vcc, the base is connected to the specific potential Vcca, and the emitter is connected to the second power supply potential Vgnd via the current passing means Isa. A temperature detection NPN bipolar transistor (hereinafter, referred to as a temperature detection transistor) Qsa, and a comparator CMP1 that compares the emitter potential Vsa of the temperature detection transistor Qsa with a reference potential Vref and outputs a thermal protection signal Stsd. It is characterized by having.
[0017]
An IC with a thermal protection function according to a second aspect of the present invention includes a power transistor QA, an NPN-type bipolar transistor for temperature detection (hereinafter referred to as a temperature detection transistor) Qsa arranged via an isolation region 11 with respect to the power transistor QA, A comparator CMP1 for comparing the emitter potential Vsa of the temperature detection transistor Qsa with the reference potential Vref and outputting a thermal protection signal Stsd, wherein the collector of the temperature detection transistor is connected to the first power supply potential Vcc; The base is connected to the specific potential Vcca, and the emitter is connected to the second power supply potential Vgnd via the current passing means Isa.
[0018]
The IC with a thermal protection function according to claim 3, wherein the plurality of power transistors QA to QH and the plurality of NPN bipolar transistors for temperature detection arranged respectively with the plurality of power transistors QA to QH via the isolation region 11. (Hereinafter referred to as temperature detecting transistors) Qsa to Qsh are compared with the emitter potentials Vsa to Vsh of the plurality of temperature detecting transistors Qsa to Qsh and the reference potential Vref, and at least one of the emitter potentials Vsa to Vsh is compared. And a comparator CMP3 that outputs a thermal protection signal Stsd when the condition is satisfied. The temperature detection transistor has a collector connected to the first power supply potential Vcc point, a base connected to the specific potential Vcca point, and an emitter connected to the specific potential Vcca point. The second power supply potential Vgnd is connected via the current passing means Isa.
[0019]
According to a fourth aspect of the present invention, the specific potential Vcca is the first power supply potential Vcc.
[0020]
An IC with a thermal protection function according to claim 5 is the IC with a thermal protection function according to claim 1, wherein the reference potential Vref is a constant voltage generated by the bandgap constant voltage circuit CV <b> 1 from the first power supply potential Vcc. It is characterized by being obtained by lowering by Vbg.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an IC with a thermal protection function of the present invention will be described with reference to the drawings.
[0022]
FIG. 1 is a diagram showing the configuration of the thermal protection circuit according to the first embodiment of the present invention, and FIG. 2 is a characteristic diagram for explaining the operation of FIG.
[0023]
In FIG. 1, an NPN bipolar transistor for temperature detection (hereinafter, temperature detection transistor) Qsa is arranged near a power NPN bipolar transistor (hereinafter, power transistor) QA so as to be thermally coupled. I have. The collector and the base of the temperature detecting transistor Qsa are connected to a power supply potential Vcc point which is a first power supply potential, and the emitter is connected to a ground potential Vgnd point which is a second power supply potential via a current source Isa which is a current passing means. You.
[0024]
The emitter potential Vsa of the temperature detection transistor Qsa is input as a comparison input of the comparator CMP1. The emitter potential Vsa has a value obtained by subtracting the base-emitter voltage Vbe of the temperature detection transistor Qsa from the power supply potential Vcc. On the other hand, a reference potential Vref is input as a reference input of the comparator CMP1. The reference potential Vref is a value obtained by subtracting the constant voltage Vbg of the constant voltage circuit CV1 or a voltage obtained by dividing the constant voltage Vbg from the power supply potential Vcc. Note that the comparator CMP1 is preferably provided with a hysteresis characteristic in order to obtain a stable comparison result.
[0025]
Referring to FIG. 2 as well, reference potential Vref is maintained at a constant value (= Vcc-Vbe) if power supply potential Vcc is constant because constant voltage Vbg is constant. On the other hand, since the base-emitter voltage Vbe has a negative temperature characteristic of about −2 mV / ° C., the temperature of the temperature detection transistor Qsa rises as the temperature of the thermally coupled power transistor QA rises, The base-emitter voltage Vbe decreases. Therefore, the emitter potential Vsa (= Vcc-Vbe) increases as the temperature increases.
[0026]
When the junction temperature Tj of the power transistor QA is room temperature T1 (eg, 25 ° C.), the emitter potential Vsa is lower than the reference potential Vref, the output of the comparator CMP1 is at a high (H) level, and the thermal shutdown signal (thermal protection signal) ) Stsd is not output.
[0027]
As the junction temperature Tj of the power transistor QA increases, the emitter potential Vsa approaches the reference potential Vref. When the junction temperature Tj reaches the temperature T2 (eg, 175 ° C.) to be protected, the emitter potential Vsa reaches the reference potential Vref, the output of the comparator CMP1 is inverted to a low (L) level, and the thermal shutdown signal Stsd Is output. The drive signal to the power transistor QA is turned off by this thermal shutdown signal Stsd to protect it from thermal destruction.
[0028]
In the present invention, even if a parasitic transistor Qps is formed between the power transistor QA and the temperature detection transistor Qsa in the same manner as in FIG. 10, the collector of the temperature detection transistor Qsa is connected to the power supply potential Vcc. Even if the parasitic transistor Qps conducts, it does not affect the temperature detection operation of the temperature detection transistor Qsa. Therefore, the temperature detection transistor Qsa can be arranged very close to the power transistor QA, and the overheat protection of the power transistor QA can be performed more accurately.
[0029]
Further, since the emitter potential Vsa and the reference potential Vref are based on the same power supply potential Vcc, even if the power supply potential Vcc fluctuates for some reason, the comparison result of the comparator CMP1 is not affected.
[0030]
In FIG. 1, a constant reference potential Vref is obtained using the constant voltage Vbg of the bandgap constant voltage circuit CV1. However, the present invention is not limited to this, and the reference potential Vref is, as shown by a broken line in FIG. Any material may be used as long as it gives characteristics that cross the emitter potential Vsa at the temperature T2 to be protected (eg, 175 ° C.).
[0031]
FIG. 3 is a diagram illustrating a configuration of the thermal protection circuit according to the second embodiment of the present invention. In FIG. 3, the base of the temperature detection transistor Qsa and the constant voltage circuit CV1 are connected to a specific potential Vcca different from the power supply potential Vcc. Other points are the same as those in FIG.
[0032]
When the base of the temperature detection transistor Qsa and the constant voltage circuit CV1 are connected to the specific potential Vcca in this way, the influence of ripples and the like appearing on the power supply potential Vcc can be removed, and thus comparison detection can be performed more stably. Since the power supply circuit for applying the specific potential Vcca requires only a very small capacity, it is not necessary to consider the influence on the chip size of the IC. It should be noted that the collector of the temperature detection transistor Qsa may be connected to the power supply potential Vcc since even a slight voltage fluctuation does not affect the comparison detection.
[0033]
FIG. 4 is a diagram showing a partial cross section of an IC with a thermal protection function according to a third embodiment of the present invention. FIG. 5 is a diagram showing a partial cross section of an IC when a conventional thermal protection circuit for comparison with the present invention is applied.
[0034]
4, a power transistor QA and a temperature detection transistor Qsa are formed on a p-type substrate (Psub) 10 with a p-type isolation region 11 interposed therebetween. The isolation region 11 is connected to the ground potential Vgnd so as to electrically isolate the elements.
[0035]
In the power transistor QA, a high-concentration n-type buried layer 21 is formed on a P-type substrate 10, and an n-type epitaxial layer (hereinafter, epilayer) 22 is formed thereon. A p-type base region 23 is formed in the epi layer 22, and an n-type emitter region 24 is formed therein. An n-type collector region 25 is formed so as to be continuous with the buried layer 21. In the power transistor QA, the emitter region 24 is connected to the ground potential Vgnd. The base region 23 and the collector region 25 are respectively connected to predetermined locations (for example, see FIG. 11) for driving a load.
[0036]
In the temperature detecting transistor Qsa, a high-concentration n-type buried layer 31 is formed on a P-type substrate 10, and an n-type epi layer 32 is formed thereon. A p-type base region 33 is formed in the epi layer 32, and an n-type emitter region 34 is formed therein. An n-type collector region 35 is formed so as to be continuous with the buried layer 31. In the temperature detection transistor Qsa, as shown in FIG. 1, the base region 33 and the collector region 35 are connected to the power supply potential Vcc. The emitter region 34 is connected to a ground potential Vgnd via a current source as shown in FIG. 1, and the emitter potential Vsa is output.
[0037]
A parasitic transistor Qps is also formed between the power transistor QA, the isolation region 11 and the temperature detection transistor Qsa in FIG. 4, and the base of the parasitic transistor Qps is grounded in the isolation region 11. Therefore, when a motor or an inductance load is driven by the power transistor QA in the same manner as described with reference to FIG. 11, there is a timing at which the collector potential Vqa of the power transistor QA becomes a negative potential. In this case, due to conduction of the parasitic transistor Qps, a current path is formed from the collector of the temperature detection transistor Qsa to the collector of the power transistor QA, as indicated by the broken line in the figure.
[0038]
In the present invention, since the collector of the temperature detection transistor Qsa is connected to the power supply potential Vcc point together with its base, the power supply potential Vcc hardly changes even when pulled by the parasitic transistor Qps. Further, the emitter potential Vsa is not substantially affected by the conduction of the parasitic transistor Qps, so that the thermal shutdown signal Stsd is not erroneously output.
[0039]
As described above, since the temperature detection transistor Qsa of the present invention is not affected by the parasitic transistor Qps, the temperature detection transistor Qsa can be disposed very close to the isolation region 11, for example, at a distance of several μm. For example, as an example of the dimensions, the temperature detection transistor Qsa may be about the size of a basic cell and may be 10 to 20 μm, and the isolation region 11 is about several μm. On the other hand, the power transistor QA differs depending on the current and voltage to be controlled. For example, the width is about 20 times the temperature detection transistor Qsa, the depth is about 50 times the temperature detection transistor Qsa, and the area is 1000 times the area. . Therefore, the center distance L1 between the isolation region 11 and the temperature detection transistor Qsa is also small (for example, about 10 μm).
[0040]
Therefore, by arranging the temperature detection transistor Qsa very close to the power transistor QA, the temperature of the PA can be faithfully monitored by the temperature detection transistor Qsa, so that the power transistor PA can be more accurately protected from overheating.
[0041]
On the other hand, FIG. 5 shows a partial cross section of an IC when the conventional overheat protection circuit of FIG. 10 is used to avoid a malfunction due to the parasitic transistor Qps.
[0042]
In FIG. 5, the structure itself of the power transistor QA, the isolation region 11 and the temperature detection transistor Qsa is the same as that of FIG. The emitter region 34 is connected to the ground potential Vgnd point, the base region 33 is connected to the reference potential Vref point, and the collector potential Vqsa of the collector region 35 is used for detecting the protection operation. 4 is different from FIG. 4 of the present invention.
[0043]
In the configuration example of FIG. 5, the temperature detection transistor Qsa is arranged at a position where malfunction due to the parasitic transistor Qps can be avoided. As a reference example, as a specific numerical example, the current i1 drawn to the collector of the power transistor QA is 50 mA, and the current i2 flowing through the parasitic transistor Qps to prevent the temperature detection transistor Qsa from malfunctioning due to the parasitic transistor Qps. If the limit is 50 μA, the current amplification factor hfe of the parasitic transistor Qps becomes 0.001. In order to keep the current amplification factor hfe of the parasitic transistor Qps at a small value as in the example, it is necessary to provide the temperature detection transistor Qsa at a long distance L2 (= several 100 μm to 1 mm) from the isolation region 11. Of course, these numerical values are for reference only, and vary depending on the current value, the characteristics of each element, and the like. However, the basic problem that the temperature detection transistor Qsa needs to be provided separately is different. Absent. This distance L2 is much longer than the distance L1 in FIG. 4 of the present invention.
[0044]
As described above, when the conventional overheat protection circuit of FIG. 10 is used, the temperature detection transistor Qsa has to be disposed at a long distance L2 from the power transistor QA, and the accuracy of temperature detection is greatly reduced. It does not provide accurate thermal protection and, in turn, leads to an increase in chip size. These conventional disadvantages have been solved in the present invention, as also described in FIG.
[0045]
FIG. 6 is a diagram showing a partial cross section of an IC with a thermal protection function according to a fourth embodiment of the present invention. FIG. 6 differs from FIG. 4 in that the power transistor QA is constituted by an N-channel MOS transistor, and the isolation region 11 is omitted in this connection. The point that the temperature detection transistor Qsa and the parasitic transistor Qps are formed is the same as in FIG.
[0046]
In FIG. 6, the power transistor QA includes an n-type drain region 42 formed on the P-type substrate 10, an n-type source region 41, and a gate 43 provided above a channel therebetween. The operations and effects in FIG. 6 are the same as those in FIG. 4, and therefore the description is omitted for simplicity.
[0047]
FIG. 7 is a diagram showing a configuration of a thermal protection circuit for a plurality of power transistors according to a fifth embodiment of the present invention, and FIG. 8 is a diagram schematically showing an arrangement configuration in FIG.
[0048]
7 and 8, a plurality (for example, four) of power transistors QA to QD are provided at corners of the IC chip 100, and temperature detection transistors Qsa to Qsd are provided close to each other.
[0049]
Current sources Isa to Isd are provided in series corresponding to the temperature detection transistors Qsa to Qsd, and their emitter potentials Vsa to Vsd are supplied to each (-) input terminal of the comparator CMP2.
[0050]
The reference potential Vref is input to the (+) input terminal of the comparator CMP2. This reference potential Vref is formed in the same manner as in FIG. 1 or FIG. In the comparator CMP2, the highest emitter potential among the plurality of emitter potentials Vsa to Vsd is compared with the reference potential Vref, and a comparison output is obtained.
[0051]
The configuration and thermal protection operation of each transistor in FIGS. 7 and 8 are the same as those in the first to fourth embodiments.
[0052]
The present invention is characterized in that, even in an IC having a plurality of power transistors, the temperature detection transistors Qsa to Qsd may be as large as a basic cell, and are arranged very close to the power transistors QA to QD to be protected. A high-precision thermal protection circuit can be configured without causing an increase in chip size.
[0053]
FIG. 9 is a view schematically showing an arrangement of a thermal protection circuit for a plurality of power transistors as in FIG. 8, according to the sixth embodiment of the present invention.
[0054]
In the arrangement of FIG. 9, a plurality of power transistors QA to QD are provided on the upper side of the IC chip 200, and a plurality of power transistors QE to QH are provided on the lower side. Temperature detection transistors Qsa to Qsh are provided near these power transistors QA to QH, respectively. The emitter potentials of the temperature detection transistors Qsa to Qsh are respectively input to the comparator CMP3, and a thermal protection operation is performed.
[0055]
In addition to the arrangements shown in FIGS. 7 and 9, in the present invention, the temperature detection transistors Qsa to Qsd are small and can be arranged very close to each power transistor, so that any arrangement can be adopted.
[0056]
【The invention's effect】
According to the present invention, even if a parasitic transistor is formed between the power transistor and the temperature detection transistor as in the related art, the collector of the temperature detection transistor is connected to the power supply potential point, so that the parasitic transistor becomes conductive. This does not affect the temperature detection operation of the temperature detection transistor. Therefore, the temperature detection transistor can be arranged very close to the power transistor (for example, several μm), and the temperature of the power transistor can be faithfully monitored by the temperature detection transistor to more accurately protect the power transistor from overheating. it can.
[0057]
In addition, since the emitter potential and the reference potential are based on the same power supply potential or another specific potential point, even if the power supply potential or the like fluctuates for some reason, the comparison result of the comparator is not affected.
[0058]
In particular, even in an IC having a plurality of power transistors, the temperature detection transistor may be as large as a basic cell, and is disposed very close to each power transistor to be protected, which leads to an increase in chip size. Thus, a highly accurate thermal protection circuit can be configured.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a thermal protection circuit according to a first embodiment of the present invention.
FIG. 2 is a characteristic diagram for explaining the operation of FIG. 1;
FIG. 3 is a configuration diagram of a thermal protection circuit according to a second embodiment of the present invention.
FIG. 4 is a partial cross-sectional view of an IC according to a third embodiment of the present invention.
FIG. 5 is a partial cross-sectional view of an IC when a malfunction is avoided using a conventional overheat protection circuit.
FIG. 6 is a partial cross-sectional view of an IC according to a fourth embodiment of the present invention.
FIG. 7 is a diagram showing a configuration of a thermal protection circuit for a plurality of power transistors according to a fifth embodiment of the present invention.
FIG. 8 is a diagram schematically showing an arrangement configuration in FIG. 7;
FIG. 9 is a view schematically showing another arrangement configuration for a plurality of power transistors according to the sixth embodiment of the present invention.
FIG. 10 is a diagram showing a configuration of a conventional thermal protection circuit.
FIG. 11 is a diagram showing a load drive circuit using a PA according to the related art and the present invention.
[Explanation of symbols]
QA to QH Power transistors Qsa to Qsh Temperature detection transistor Qps Parasitic transistors Isa to Isd Current sources CMP1 to CMP3 Comparator CV1 Constant voltage circuit Vref Reference potentials Vsa to Vsd Emitter potential Stsd Thermal shutdown signal 100, 200 IC chip 10 P-type substrate 11 Isolation regions 21, 31 Buried layers 22, 32 Epi layers 23, 33 Base regions 24, 34 Emitter regions 25, 35 Collector regions

Claims (5)

A NPN bipolar transistor for temperature detection (hereinafter referred to as a temperature detection transistor) having a collector connected to a first power supply potential point, a base connected to a specific potential point, and an emitter connected to a second power supply potential point via current passing means. )When,
A comparator for comparing the emitter potential of the temperature detecting transistor with a reference potential and outputting a thermal protection signal, the semiconductor integrated circuit having a thermal protection function. A power transistor, an NPN-type bipolar transistor for temperature detection (hereinafter referred to as a temperature detection transistor) arranged via an isolation region with respect to the power transistor, and comparing the emitter potential and the reference potential of the temperature detection transistor with each other. A comparator that outputs a protection signal,
The temperature detection transistor has a collector connected to a first power supply potential point, a base connected to a specific potential point, and an emitter connected to a second power supply potential point via current passing means. Semiconductor integrated circuit with thermal protection function. A plurality of power transistors, a plurality of NPN-type bipolar transistors for temperature detection (hereinafter referred to as “temperature detection transistors”) respectively disposed via isolation regions with respect to the plurality of power transistors, and emitters of the plurality of temperature detection transistors A comparator that compares the potential with the reference potential and outputs a thermal protection signal when at least one of the emitter potentials satisfies the comparison condition;
The temperature detection transistor has a collector connected to a first power supply potential point, a base connected to a specific potential point, and an emitter connected to a second power supply potential point via current passing means. Semiconductor integrated circuit with thermal protection function. 4. The semiconductor integrated circuit with a thermal protection function according to claim 1, wherein the specific potential is a first power supply potential. 5. The semiconductor integrated circuit with a thermal protection function according to claim 1, wherein the reference potential is obtained by lowering the first power supply potential by a constant voltage generated by a band gap constant voltage circuit.

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