JPS6328124A - Voltage detecting circuit - Google Patents

Abstract

PURPOSE:To reduce the power source voltage dependency of the difference potential between a logical threshold value and a source potential and to widen the range of a usable power source potential by utilizing the forward voltage of a PN junction diode. CONSTITUTION:The PN junction diode 9 is interposed between the source electrode of a 2nd MOS transistor(TR) 2 and a 2nd voltage source 14 in the direction so as to allow the current to flow. In this case, the logical threshold value is (power source potential)+(forward voltage of PN junction diode 9)+(increment in threshold voltage of the 2nd MOS TR 2). The dependency upon the forward current value of the PN junction diode is small comparatively and an increment in threshold voltage with the back gate voltage of the 2nd MOS TR 2 is about 0.1-0.3<v>, so the logical threshold value has an about +0.5<v>-1.0<v> difference potential to the power source potential. This difference potential does not utilize the difference in the mutual conductance between the MOS TRs, so the power source potential dependency is very small and deviation due to manufacture variance can be suppressed small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a voltage detection circuit formed in a semiconductor integrated circuit device using complementary MOS transistors.

[Conventional technology]

In recent years, semiconductor integrated circuit devices have become increasingly highly integrated and densely packed. By integrating more functions into a single semiconductor integrated circuit device, the number of input/output terminals required by the device is increasing, but there are physical limits. Therefore, there is a growing demand for multiplexing input and output signals at the same terminal.

There is a voltage detection circuit shown in FIG. 3 that is formed in a semiconductor integrated circuit device using conventional complementary MOS transistors. In FIG. 3, the voltage detection circuit has a first conductivity type (N type or P type) whose gate electrode and drain electrode are connected to the first connection point 11 and whose source electrode is connected to the first voltage source 13. A MOS transistor 1 has a gate electrode connected to a signal input terminal 15, a drain electrode connected to a first connection point 11, and a source electrode connected to a second voltage source 14.
A second M of opposite conductivity type (P type or N type) connected to
The OS transistor 2 and the gate electrode are the first connection point 11
a third MOS transistor 3 of one conductivity type, whose drain electrode is connected to the output end 17 and whose source electrode is connected to the first voltage source 13; and whose gate electrode is connected to the comparison voltage generation end 16 and whose drain electrode is connected to the output end 17 and the source electrode is connected to the second voltage source 14 . A voltage detection unit 19 comprising a fourth MOS transistor 4 of an opposite conductivity type, and a gate electrode and a drain electrode are connected to the second connection point 12 . a fifth MOS transistor 5 of one conductivity type, whose source electrode is connected to the first voltage source 13 , whose gate electrode is connected to the reference voltage input terminal 18 and whose drain electrode is connected to the second connection point 12 . A sixth MOS transistor of opposite conductivity type is connected and has a source electrode connected to the second voltage source 14, a gate electrode connected to the second connection point 12, and a drain electrode connected to the comparison voltage generation end 16. A seventh MOS transistor of one conductivity type has a source electrode connected to the first voltage source 13, a gate electrode and a drain electrode connected to the comparison voltage generating terminal 16, and a source electrode connected to the second voltage source 13. source 14
and a comparison voltage generating section 20 consisting of an eighth transistor 8 of opposite conductivity type connected to.

For convenience of explanation, it is assumed that the voltage detection circuit shown in FIG. 3 is configured such that the voltage detection section 19 and the comparison voltage generation section 20 are symmetrical.

That is, it is assumed that the first MOS transistor 1 and the fifth MOS transistor 5 have the same mutual conductance under the same bias condition, and similarly, the combination of the second MOS transistor 2 and the sixth MOS transistor 5 is assumed to have the same mutual conductance under the same bias condition. , 3rd
MOS transistor 3 and seventh MOS transistor 7
It is assumed that the three pairs of the fourth MOS transistor 4 and the eighth MOS transistor 8 have the same mutual conductor yx. Here, the same mutual conductance can be realized by, for example, making the channel width and channel length of the MOS transistors the same, or by making the ratio thereof the same.

Further, it is assumed that the input voltage applied to the signal input terminal 15 and the reference voltage applied to the reference voltage input terminal 18 are the same voltage. In a voltage detection circuit having such a symmetrical configuration, its logical threshold value is the same value as the reference voltage applied to the reference voltage input terminal 18.

The operation of the voltage detection circuit shown in FIG. 3 will be explained below using the current-voltage characteristics of the MOS transistor shown in FIG. 4. The fifth and seventh MOS transistors 5 and 7 constitute a current mirror circuit, and both are set so that their operating bias states are in the saturation region.
The current flowing through the transistor is assumed to be 17, and the fifth. If the mutual conductances of the seventh MOS transistors 5 and 7 are ggms and gmt, respectively, and the current flowing through the fifth MOS transistor 5 is is, then i 7 == (g
rngms)・is. Therefore, the current-voltage characteristics of the sixth MOS transistor 6 determined by the voltage applied to the reference voltage input terminal 18 and the current-voltage characteristics of the fifth MOS transistor 6 are determined by the voltage applied to the reference voltage input terminal 18.
The potential of the second connection point 12 is determined by the current-voltage characteristics of the transistor 5, and by applying that potential to the gate electrode, the seventh MOS transistor
A current of m'/gms)·i5 will flow.

Since the MOS transistors 4 and 8 of the fourth and WJ8 have the same mutual conductance and form a current mirror circuit, the characteristic 27 of the seventh MOS transistor and the characteristic 27 of the eighth MOS transistor as shown in the current-voltage characteristic diagram of FIG. The potential V1g shown at the intersection with characteristic 28 is the comparison voltage generation end 1.
By receiving this potential at the gate electrode, the fourth MOS transistor 4 exhibits characteristic 24. The first component that constitutes the voltage detection section 19. Second. Third
MOS transistor 1. 2. Since the operating state of No. 3 has a symmetrical configuration, the operating state of No. 5. 6th. 7th MOS
Transistor 5. 6. It is the same as the operating state of 7,
Therefore, the current-voltage characteristic 23 of the third MOS transistor 3 is the same as the characteristic 27 of the seventh MOS transistor. Therefore, the potential Vtt at the output terminal 17 is the same as the potential V16 at the comparison voltage output terminal 16, and this potential is designed to be the input threshold voltage of the next stage logic circuit (not shown).

Now, when the potential of the input terminal 15 becomes lower than the potential of the reference voltage input terminal 18, the mutual conductance of the second MOS transistor 2 becomes small. second M
The current flowing through the OS transistor 1.2 decreases, and as a result, the current flowing through the third MOS transistor constituting the current mirror circuit also decreases, and its current-voltage characteristic changes from 23 to 23'. Therefore, the potential of the output terminal 17 indicated by the intersection of 23 and 24 in the current-voltage characteristic is V1? More■1? ’. Similarly, input terminal 1
When the potential of the third MOS transistor becomes higher than the potential of the reference voltage input terminal 18, the characteristic of the third MOS transistor changes to 23'', and the potential of the output terminal 17 changes to V1/.

As explained above, in the symmetrically configured voltage detection circuit, the potential applied to the reference voltage input terminal 18 becomes the logical threshold, and the potential 1<the potential of the first voltage source 13 and the second voltage If the potential of the source 14 is set between the potential of the MO3 transistor of the opposite conductivity type and the voltage of the MO3 transistor of the opposite conductivity type by means of resistor division or the like, it can be easily constructed.

Next, as a form in which this voltage detection circuit is actually applied, a potential different from the potential applied to the reference voltage input terminal 18,
Mainly regarding the case where a high potential is set as the logic threshold (hereinafter, the potential of the first voltage source 13 is referred to as the power supply potential when the second voltage source 14t is set to the ground potential). explain.

In this case, the reference voltage input terminal 18 is connected to the first voltage source 13.
For example, if the mutual conductance of the MOS transistor 2 is configured to be the same as the mutual conductance of the sixth MOS transistor under the condition that a potential serving as a logic threshold is applied to the signal input terminal 15. realizable. This also applies to the other first and fifth MOS)
It goes without saying that this can be achieved by adjusting the mutual conductance of any one or more of the 1.50 sets of range metals, the 3.70 sets of third and seventh MOS transistors, and the fourth and eighth MOS transistor sets.

In this way, when a potential higher than the power supply potential is used as the logic threshold, the difference potential between the power supply potential and the logic threshold can be generated by the difference in mutual conductance of the MOS transistors under the same bias condition. A method of obtaining the same mutual conductance under different bias conditions is to vary the ratio of the channel width to channel length of the MOS transistor, or to vary the impurity concentration directly under the gate region of the MOS transistor.
For example, the threshold voltage of the transistor itself may be changed.

[Problem that the invention seeks to solve]

The conventional voltage detection circuit described above has the following drawbacks.

That is, when changing the threshold voltage t of a MOS transistor,
Since it is required that the transconductance of the transistors be different, an additional process is required for this purpose, and furthermore, the threshold voltage has a predetermined deviation width due to manufacturing variations. Even when the ratio of the channel width and channel length of M
Since the mutual conductance of the OS transistor is dependent on the power supply potential, the logic threshold 31 has a relatively large deviation width 32t- as shown in FIG. The difference potential between 34
becomes small, and in the region of high power supply potential, the logic threshold 3
The difference potential 34 between 1 and the power supply potential 33 shows a tendency to increase, and as a result, the difference potential between the logic threshold and the power supply potential in a region where the power supply potential is low becomes less than the noise margin,
This has the disadvantage that the lower limit of the power supply potential that can be used by the voltage detection circuit is determined.

In experiments conducted by the inventor, if the lower limit of the logic threshold when the power supply potential is 2.5V is 3.2V, the power supply potential is 6, Ov.
The lower and upper limits of the threshold potential are 1ov and 125v.
With noise, if the margin is t-10v or more, it becomes unusable when the power supply potential is less than 3.5V, and in the region of high power supply potential, the upper limit of the power supply potential that can be used is determined by the gate breakdown voltage of the MOS transistor. It turned out that it was possible.

SUMMARY OF THE INVENTION An object of the present invention is to provide a voltage detection circuit that can reduce the dependence of the difference potential between a logic threshold value and a power supply potential on the power supply potential, thereby expanding the range of usable power supply potentials.

Means for Solving All Problems c] The voltage detection circuit of the present invention has a first voltage detection circuit of one conductivity type, in which a gate electrode and a drain electrode are connected to a first connection point, and a source electrode is connected to a first voltage source. a second *os transistor of opposite conductivity type, whose gate electrode is connected to the signal input terminal, whose drain electrode is connected to the first connection point, and whose source electrode is connected to a second voltage source; a third MOS transistor of one conductivity type, whose gate electrode is connected to the first connection point, whose drain electrode is connected to the output end, and whose source electrode is connected to the first voltage source; and whose gate electrode is connected to a comparison voltage. a fourth MOS transistor of an opposite conductivity type connected to the generating end, having a drain electrode connected to the output end and a source electrode connected to the second voltage source; and a fourth MOS transistor having a gate electrode and a drain electrode connected to a second connection point. a fifth M of one conductivity type connected and having a source electrode connected to the first voltage source;
an OS transistor, and a sixth MOS transistor of opposite conductivity type, the gate electrode of which is connected to the first voltage source, the drain electrode of which is connected to the second connection point, and the source electrode of which is connected to the second voltage source. a seventh MOS transistor of one conductivity type, whose gate electrode is connected to the second connection point, whose drain electrode is connected to the comparison voltage generation end, and whose source electrode is connected to the first voltage source; and an eighth MOS transistor of opposite conductivity type, the electrode and the drain electrode of which are connected to the comparison voltage generation end and the source electrode of which is connected to the second voltage source. , a PN junction diode connected in a direction that allows a forward current to flow between the source electrode of one of the second MOS transistor or the sixth MOS transistor and a second voltage source. The mutual conductances of the transistor pairs in each of the transistor set, the second and sixth MOS transistor set, the third and seventh MOS transistor set, and the fourth and eighth MOS transistor set are configured to be equal. You can also

Further, the voltage detection circuit of the present invention includes a set of first and fifth MOS transistors, a set of second and sixth l1d08 transistors, a set of third and seventh MOS transistors, and a set of fourth and eighth MOS transistors. It is also possible to configure at least one pair of transistors in the set to have different mutual conductances.

Further, in the voltage detection circuit of the present invention, the PN junction diode is
A bipolar Φ formed by a well region of an opposite conductivity type formed in a semiconductor substrate of one conductivity type and a source/drain diffusion layer region of one conductivity type formed in the well region.
It can also be constructed by a pace-emitter junction of a transistor.

〔Example〕

An embodiment of the present invention will be described using nine pages.

In the voltage detection circuit of the present invention, the forward voltage of the PN junction diode and the threshold voltage of the MOS transistor by using this forward voltage as the back gate voltage are used as elements constituting the difference potential between the logic threshold value and the power supply potential. This is to make use of the increased amount.

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

This embodiment consists of a voltage detection section 19' and a comparison voltage generation section 20', and the first to eighth MOS transistors 1 to 8 have the same circuit connections as the conventional voltage detection circuit shown in FIG. The reference voltage input terminal 18 shown in FIG. 3 is connected to the first voltage source 13.

Furthermore, in this embodiment, unlike the conventional circuit, the PN junction diode 9 is inserted between the source electrode of the second MOS transistor 2 and the second voltage source 14 in a direction that allows forward current to flow. It is something that

Next, the operation of the voltage detection circuit of this embodiment will be explained.

In this voltage detection circuit, except for i and the PN junction diode 9,
The other first to eighth MOS transistors 1 to 8 are the third MOS transistors.
As explained in the circuit shown in the figure, in the case of a symmetrical configuration, the potential of the source electrode of the second MOS transistor 2 is P
% higher than the potential of the second voltage source 14 by the forward potential of the N-junction diode 90, and due to the back gate characteristics of the MOS transistor, its threshold voltage is higher than that of the sixth voltage source 14 with the same transconductance under the same bias condition. It becomes higher than the threshold voltage of MOS transistor 6. Therefore.

to the logical threshold in this case.

(Power supply potential) + (forward voltage of PN junction diode 9)
+(increase in voltage of second MOS transistor 2). The value of the forward voltage of a PN junction diode has a large temperature dependence, but its dependence on the forward current value is relatively small, and it is used as a reference voltage source in semiconductor integrated circuit devices as appropriate, and is suitable for manufacturing methods. Although it varies greatly, it shows approximately O14 to 0.7v. Also, the second
Since the increase in the threshold voltage due to the back gate voltage of 0.4 to 0.7V of the MOS transistor 2 is about 0.1 to 0.3V, as a result, the logic threshold is approximately +0.5V to +0.5V with respect to the power supply potential. It has a potential difference of about LOv. Since this differential potential d and the difference in mutual conductance of the MO3 transistors are not utilized, dependence on the power supply potential is extremely small, and manufacturing variations and deviations can also be suppressed to a small level.

In addition, if the difference potential between the logic threshold and the power supply voltage is set to be larger due to the necessity of noise margin, etc., this can be achieved by giving a difference to the mutual conductance of the four transistor pairs as described above. In this case, the difference in mutual conductance can be made smaller than in the case shown in the conventional example, so it is possible to configure a voltage detection circuit in a state that is nearly symmetrical, so that the logic threshold and tS potential can be It is possible to suppress the dependence of the potential difference with the power supply potential to a small extent.

Furthermore, since the forward voltage of the PN junction diode and the mutual conductance of the MOS transistor change in opposite directions with respect to temperature changes, the temperature dependence of the voltage detection circuit can be offset by adjusting the dimensions of both elements. It is also possible.

Furthermore, in the above embodiment, the PN junction diode 9t1 second
The source electrode of the MOS transistor 2 and the second voltage source 1
4, but it can also be inserted between the source electrode of the sixth MOS transistor 6 and the second voltage source 14. When the circuit configuration is symmetrical, the logic threshold in this case is (power supply potential) - (forward voltage of PN junction diode 9) - (ff of the sixth MOS transistor)
What is given by a[voltage increase] does not require much explanation.

Furthermore, for those skilled in the art, by setting the second voltage source 14 to the ground potential, setting the first voltage source 13 to a negative potential, and inserting the PN junction diode 9 in the opposite direction, it is possible to detect voltage on the negative potential side. It is also clear that this can be done.

Next, it will be explained with reference to the drawings that the PN junction diode 9 of this example can be manufactured without adding any new process. FIG. 2 is a sectional view showing the structure of a PN junction diode used in the voltage detection circuit of this embodiment. In FIG. 2, reference numeral 41 denotes a semiconductor substrate of one conductivity type, and a source/drain of a MOS transistor (not shown) of one conductivity type is diffused in a well region 42 of an opposite conductivity type formed in this semiconductor substrate 41 of one conductivity type. When the layer is formed, a diffusion region 43 of one conductivity type is formed in the same process. Therefore, the semiconductor substrate 41 of one conductivity type, the well region 42 of opposite conductivity type, and the diffusion region 43 of one conductivity type are used as collector, paste, and emitter, respectively. A vertical bipolar transistor can be constructed.

44 and 45 are one conductivity type diffusion region and the opposite conductivity type diffusion region, respectively, and 1! It is provided for the purpose of making an electrical connection. The opposite conductivity type well region 42, the one conductivity type diffusion regions 43 and 44, and the opposite conductivity type diffusion region 45 are all one conductivity type MOS transistor and the opposite conductivity type MOS transistor.
This is formed at the same time as the S transistor is manufactured.

The PN junction diode 9 used in the voltage detection circuit of this embodiment is constituted by a PN junction between the opposite conductivity type well region 42 which becomes the base region of the bipolar transistor configured as described above and the one conductivity type diffusion region 43 which becomes the emitter region. be done.

〔Effect of the invention〕

As explained in detail above, the present invention can reduce the dependence of the difference potential between the logic threshold and the power supply potential by utilizing the forward voltage of the PN junction diode, and therefore can be used. This has the effect of widening the range of power supply potentials. Furthermore, there is an effect that the fluctuation of the logic 1dl([ can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a cross-sectional view of the PN junction diode 9 shown in FIG. 1, FIG. 3 is a circuit diagram of a conventional voltage detection circuit, and FIG. FIG. 5 is a current-voltage characteristic diagram for explaining the operation of the voltage detection circuit shown in FIG. 1-8・-・・MOS transistor, 9・・・・・・
PN junction diode, 11.12... connection point,
13.14-... Voltage source, 15...- Signal input end, 16... Comparison voltage generation end, 17...
---Output end, 19.19'--Voltage detection section, 2
0.20'-... Comparison voltage generation section. Kuzu'2 Ward

Claims (1)

[Claims] 1. A first MOS transistor of one conductivity type whose gate electrode and drain electrode are connected to a first connection point and whose source electrode is connected to a first voltage source, and whose gate electrode is connected to a signal input point. a second MOS transistor of an opposite conductivity type connected to the end, a drain electrode connected to the first connection point, a source electrode connected to a second voltage source; and a gate electrode connected to the first connection point. a third MOS transistor of one conductivity type, whose drain electrode is connected to the output terminal and whose source electrode is connected to the first voltage source, and whose gate electrode is connected to the comparison voltage generation terminal and whose drain electrode is connected to the output terminal. a fourth MOS transistor of an opposite conductivity type connected and having a source electrode connected to the second voltage source; a fourth MOS transistor having a gate electrode and a drain electrode connected to the second connection point and having a source electrode connected to the first voltage source; a fifth MOS transistor of one conductivity type, the gate electrode being connected to the first voltage source, the drain electrode being connected to the second connection point, and the source electrode being connected to the second voltage source; A sixth MOS transistor of opposite conductivity type is connected, and has a gate electrode connected to the second connection point, a drain electrode connected to the comparison voltage generation end, and a source electrode connected to the first voltage source. Seventh M of one conductivity type
A complementary MOS transistor comprising an OS transistor and an eighth MOS transistor of an opposite conductivity type whose gate electrode and drain electrode are connected to the comparison voltage generation end and whose source electrode is connected to the second voltage source is used. a PN junction diode connected in a direction that allows a forward current to flow between the source electrode of one of the second MOS transistor or the sixth MOS transistor and a second voltage source; A voltage detection circuit comprising: 2. Set of first and fifth MOS transistors, second and sixth MOS transistors
Voltage detection according to claim 1, in which the mutual conductances of the transistor pairs are equal in each of the four sets of MOS transistors, the third and seventh MOS transistors, and the fourth and eighth MOS transistors. circuit. 3. Set of first and fifth MOS transistors, second and sixth MOS transistors
The voltage according to claim 1, in which at least one pair of transistors among a set of MOS transistors, a set of third and seventh MOS transistors, and a set of fourth and eighth MOS transistors have different mutual conductances. detection circuit. 4. A bipolar transistor in which a PN junction diode is formed by a well region of an opposite conductivity type formed in a semiconductor substrate of one conductivity type and a source/drain diffusion layer region of one conductivity type formed in the well region. 4. The voltage detection circuit according to claim 1, wherein the voltage detection circuit is configured by a base-emitter junction.