JP3255158B2 - Semiconductor integrated circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit composed of fine MOS transistors, and more particularly to a circuit suitable for high-speed and low-power operation.

[0002]

2. Description of the Related Art 1989 International Symposium on VSI Technology, Systems and Applications, Proceedings of Technical Papers (1989
(May) Pages 188 to 192 (1989 International
Symposium on VLSI Technology, Systems and Applicat
ions, Proceedings of Technical Papers, pp.188-192
As described in (May 1989)), as the MOS transistor is miniaturized, its breakdown voltage decreases, so that the operating voltage has to be lowered. In this case,
In order to maintain high-speed operation, the threshold voltage (V _T ) of the MOS transistor needs to be reduced in accordance with the decrease in the operating voltage. This operating speed, the effective gate voltage of the MOS transistor, that is, ruled by a value obtained by subtracting the V _T from the operating voltage is because fast as this value is larger. However, when the V _T below about 0.4V, as described below, by the sub-threshold characteristics of the MOS transistor (tailing characteristics), a phenomenon that transistor completely no longer able longer to turn off the DC current to flow Occurs.

A conventional CMOS inverter shown in FIG. 49 will be described. Ideally, when the input signal IN is at a low level (= V _SS ), the N-channel MOS transistor _MN is turned off, and when the input signal IN is at a high level (= V _CC ), the P-channel MOS transistor _MN is turned off.
The S transistor M _P is turned off, and no current flows in any case. However, the MOS transistor V
_{When T} decreases, the subthreshold characteristic cannot be ignored.

As shown in FIG. 50, a drain current I _DS in a subthreshold region is proportional to an exponential function of a gate-source voltage V _GS and is expressed by the following equation.

[0005]

(Equation 1)

[0006] However, W is the channel width of the MOS transistor, I _0, W ₀ is the current value and the channel width in defining the V _T, S is tailing factor (inverse of the slope of V _GS -log I _DS characteristics) is there. Therefore, even if V _GS = 0, the sub-threshold current

[0007]

(Equation 2)

Flows. Since the transistor in the off state in the CMOS inverter of FIG. 49 is a V _GS = 0, that at the time of non-operation is a ground potential from the high supply voltage V _CC toward the low supply voltage V _SS through the above current I _L Become.
This sub-threshold current is, as shown in FIG.
The threshold voltage from V _T V _T 'Lowering the, I _L from I _L'
Exponentially. As is apparent from the above equation, in order to reduce the subthreshold current, V
_T may be increased or S may be decreased. However, the former causes a reduction in speed due to a reduction in the effective gate voltage. In particular, if the operating voltage is lowered along with the miniaturization in view of the withstand voltage, the speed drop becomes remarkable, and the advantage of the miniaturization cannot be utilized, which is not preferable. The latter is difficult for the following reasons as long as it is operated at room temperature. Tailing factor S is the capacitance C _D of the depletion layer capacitance C _OX and under the gate of the gate insulating film is represented as follows.

[0009]

(Equation 3)

Here, k is Boltzmann's constant, T is absolute temperature, and q is elementary charge. As is clear from the above equation, C _OX
Irrespective of C and C _D , S ≧ kT ln 10 / q, and it is difficult to reduce the voltage to 60 mV or less at room temperature. Due to the phenomena described above, the substantial DC current of a semiconductor integrated circuit composed of a large number of MOS transistors significantly increases. In particular, at the time of high-temperature operation, since _VT is low and S is large, this problem becomes more serious. In the future downsizing era of computers and the like in which low power consumption is important, this increase in subthreshold current is an essential problem.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide an MO
It is an object of the present invention to provide a high-speed and low-power semiconductor integrated circuit even if an S transistor is miniaturized.

[0012]

In order to achieve the above object, according to the present invention, control circuit means for controlling a current supply of a large current and a small current is inserted between a source of a MOS transistor and a power supply, so that the circuit can be used for various purposes. By switching these currents according to
Supply to OS transistor circuit. For example, a high current is supplied when high-speed operation is required, and a small current is supplied when low power consumption is required.

Since high-speed operation is required during normal operation, a large current is supplied from the current supply means to the MOS transistor circuit to enable high-speed operation. At this time, MOS
Although a DC current flows through the transistor circuit as described above, the DC current is usually sufficiently small as compared with the operating current, that is, the charge / discharge current of the load. On the other hand, since low power consumption is required during standby, the supplied current is switched to a small current to suppress the subthreshold current. At this time, since the current is limited, the logic amplitude of the MOS transistor circuit is generally smaller than that when a large current is supplied.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, FIGS.
A semiconductor integrated circuit to which the present invention is applied will be described with reference to FIGS. 35 and 40 to 43, and FIGS.
A specific embodiment will be described with reference to FIG.

FIG. 1 is a reference example suitable for explaining the principle of a semiconductor integrated circuit to which the present invention is applied. FIG.
(A) is a circuit diagram of an inverter according to a reference example. In the figure, L denotes a CMOS inverter, and a P-channel MOS
It comprises a transistor _MP and an N-channel MOS transistor _MN . As will be described later, the semiconductor integrated circuit to which the present invention is applied can be applied not only to an inverter but also to a logic gate or a group of logic gates such as NAND and NOR. However, here, the case of an inverter will be described for simplicity. S
_C and S _S are switches, _RC and R _S are resistors, and the feature of this embodiment is that switches S _C and S S are respectively connected between the power terminals V _CL and V _SL of the inverter L and the power sources V _CC and V _SS. This means that _S and the resistances R _C and R _S are inserted in parallel, thereby achieving a reduction in subthreshold current as described below. During a time period when high-speed operation is required, the switches S _C and S _S are turned on, and V _CC and V _SS are directly connected to the inverter L.
(Hereinafter, referred to as a high-speed operation mode). _MP , _MN
If the threshold voltage (V _T ) is set low, high-speed operation can be achieved. At this time, the sub-threshold current flows through the inverter L as described above. However, this is not a problem because it is usually sufficiently smaller than the operating current, that is, the charging / discharging current of the load.

On the other hand, in a time zone where low power consumption is required, the switches S _C and S _S are turned off, and power is supplied to the inverter through the resistors R _C and R _S (hereinafter referred to as a low power consumption mode). . Due to the voltage drop due to the subthreshold current flowing through the resistor, V _CL drops below V _CC and V _SL rises above V _SS . As shown in FIG.
Due to this voltage drop, the subthreshold current is reduced by the following two mechanisms. Although M _N when the input signal IN is at a low level (V _SS ) will be described, the same applies to M _P when IN is at a high level (V _CC ). (i) Since the source potential V _SL rises, a back gate bias V _BS = V _SS -V _SL = -V _M is applied, and the threshold voltage rises from V _T0 to V _T1 . The rise in the threshold voltage is

[0017]

(Equation 4)

## EQU1 ## Thereby, the subthreshold current decreases from _IL0 to _IL1 . The rate of decrease is

[0019]

(Equation 5)

## EQU1 ## Here, K is a substrate effect coefficient.
For _{example, V M = 0.3V, K =} 0.4√V, S = 100mV / deca
de, if 2ψ = 0.64V, the subthreshold current is 21
%.

(Ii) Since the source potential V _SL rises, the gate-source voltage V _GS = V _SS -V _SL = -V _M becomes negative. As a result, the subthreshold current is further increased to I _L1
To _IL2 . The rate of decrease is

[0022]

(Equation 6)

## EQU1 ## For _{example, V M = 0.3V, S =} 100m
If V / decade, sub-threshold current is 0.1%
To be reduced. Combining the effects of (i) and (ii),

[0024]

(Equation 7)

## EQU1 ## For example, V _M = 0.3V if 0.02%
become. Where V _M is the equation

[0026]

(Equation 8)

This is the solution of Incidentally, the back gates of the MOS transistors M _P and M _N of the inverter L may be connected to the respective sources (V _CL and V _SL ). However, in order to obtain the effect (i), FIG. It is more desirable to connect to V _CC and V _SS as described above.

FIG. 3 shows the effect of reducing the subthreshold current. Here, the ultra-highly integrated LSI of the future ultra-low voltage operation
The calculation is performed on the assumption that the threshold voltage V _T0 when the back gate bias is 0 is 0.05 to 0.15 V, and the total channel width W of the transistors in the off state of the entire LSI is W = 100 m. V _M The larger the resistance is increased, the effect is large. However, as shown in FIG. 1B, since the logical amplitude of the output signal OUT is smaller than the logical amplitude of the input signal IN, it is necessary to pay attention to the voltage level of the signal when connecting in multiple stages. Will be described later.

Further, the semiconductor integrated circuit to which the present invention is applied has an operation of automatically compensating for variations in the threshold voltage. That is, when the threshold voltage subthreshold current is large low voltage drop V _M due to resistance is increased, when the threshold voltage is high and the subthreshold current is small, V _M becomes smaller. In any case, the fluctuation of the current is suppressed. As is clear from FIG. 3, the fluctuation of the subthreshold current is smaller as the resistance value is larger. For example, if the resistance value is set to 3 kΩ or more, the threshold voltage becomes ± 0.
Also varies 05V, variations of the sub-threshold current I _L is suppressed to within 20% ±.

Next, a specific method of realizing the switch and the resistor described in the first embodiment will be described. FIG. 4 shows an example in which both the switch and the resistor are realized by MOS transistors. The switching MOS transistors M _C1 and M _S1 are MOS transistors having a large conductance,
Of switches S _C , S _S. In the high-speed operation mode, M _C1 and M _S1 are turned on by setting the signal φ _C to a low level and setting the signal φ _S to a high level. phi _C, the voltage level of phi _S, respectively V _SS, but may be V _CC, in order to further increase the conductance of M _C1, M _S1, the phi _C lower than V _SS, than the phi _S V _CC May be higher. The voltage for this is supplied from outside the chip, or the EEPROM or DR
What is necessary is just to generate | occur | produce by the well-known on-chip booster circuit in AM.
Conversely, in the low power consumption mode, by setting φ _C to a high level and φ _S to a low level, M _C1 and M _S1 are turned off. At this time, it must be ensured that the current can be suppressed. For that purpose, there are the following two methods.
A first method is to make φ _C higher than V _CC and φ _S lower than V _SS by an external voltage or an on-chip booster circuit. The second method is to use transistors (higher enhancement) having higher threshold voltages than those used for the inverter L as M _C1 and M _S1 . The first method has an advantage that a step for manufacturing transistors having different threshold voltages is unnecessary. On the other hand, the second method is advantageous in terms of area because a terminal for receiving an external voltage or an on-chip booster circuit is not required. The MOS transistors M _C2 and M _S2 are MOS transistors having a small conductance, and correspond to the resistances R _C and R _S in FIG. 1, respectively. These transistors have their gates connected to V _SS and V _CC , respectively, and are always on. Since these transistors do not need to be turned off, their threshold voltages can be low.

Next, a time zone in which the semiconductor integrated circuit to which the present invention is applied will be described. FIG. 5 shows signals φ _C and φ _S
The following shows an example of the timing. FIGS. 5 (a) and 5 (b)
This is a case where a semiconductor integrated circuit to which the present invention is applied is applied to a memory LSI. The memory LSI enters an operating state when the chip enable signal CE # (complementary signal) is at a low level, and enters a standby state when it is at a high level. In the case of FIG.
_C goes low in synchronization with the falling edge of CE￣, and CE goes low.
High level slightly after the rise of ￣. The signal φ _S is the opposite. Accordingly, the time zone a in the drawing is the high-speed operation mode, and the time zone b is the low power consumption mode. Generally, in a memory device using a large number of memory LSIs, a small number of LSIs are in an operating state, and the majority of the LSIs are in a standby state. Therefore, if the power consumption of the LSI in the standby state is reduced, the power consumption of the entire memory device is greatly reduced. The reason for providing a delay from the rise of CE # to the low power consumption mode is that the internal circuit of the LSI is reset during this time. FIG. 5B shows an example in which power consumption is further reduced. Here, the high-speed operation mode is set only immediately after CE # changes. That is, immediately after CE # goes low, data read /
Immediately after writing is performed and CE # goes high, the internal circuit is reset, so that these time zones are in the high-speed operation mode and the other time zones are in the low power consumption mode. Although not described here, the high-speed operation mode may be set when the address signal changes. FIG. 5C shows an example in which a semiconductor integrated circuit to which the present invention is applied is applied to a microprocessor. In the normal operation state, the clock CLK is applied. At this time, the signal φ _C is at a low level and the signal φ _S is at a high level, which is a high-speed operation mode. When the microprocessor enters the standby state or the data holding state, the clock CLK stops,
The signal BU goes high. In synchronization with this, φ _C goes high, φ _S goes low, and the device enters the low power consumption mode. As a result, the power consumption of the microprocessor is reduced, and backup can be performed for a long time with a small-capacity power supply such as a battery.

FIG. 6 is an example of a device structure for realizing the circuit of FIG. The polysilicon 130 in this figure,
131, 132, and 133 represent M _C2 , M _P ,
They correspond to the gates of M _N and M _S2 (M _C1 and M _S1 are not described here). It should be noted that M _C2 and M _P have the same n-well 101 (V + via n + diffusion layer 120).
Connected to the _CC ). M _N
And M _S2 are similarly p-substrate (connected to V _SS ) 100
Sharing. As can be seen, connecting the back gate of the MOS transistor to V _cc and V _ss not only achieves the above-mentioned effect (i) but also reduces the layout area compared to the case where the back gate is connected to the source. It is advantageous.
Although the n-well is formed in the p-substrate in the example shown here, the p-well may be formed in the n-substrate. Alternatively, ISSC, Digest
Of Technical Papers, pages 248 to 24
Page 9, February 1989 (ISSCC Digest of Technical Pa
pers, pp. 248-249, Feb. 1989) may be used.

FIG. 7 shows another method of realizing the switch and the resistor. The feature of this embodiment is that a current mirror circuit is used. I.e., the same MOS transistor threshold voltage M _C2 and M _C3 is formed in a so-called current mirror circuit sharing the gate and source, the current proportional to the current source I ₀ flows in the M _C2, the impedance large. The same applies to _MS2 and _MS3 . Therefore, M
_C2, M _S2 can be regarded as a high resistance. The current source I
_A circuit CS including ₀ , M _C3 , and M _S3 may be shared by a plurality of logic gates. The current mirror circuit is not limited to the circuit shown here, but may be another circuit. For example, a bipolar transistor may be used instead of a MOS transistor.

As described above, the method of realizing the switch and the resistor can have various modifications. In short, any means may be used as long as it allows a large current to flow during a time when high-speed operation is required and a small current during a time when low power consumption is required. In the following drawings, for simplicity, they are represented by switches and resistors as shown in FIG.

The back gate of the MOS transistor of the inverter is not limited to V _CC and V _SS , but may be connected to another power source, and its voltage may be made variable. FIG. 8 shows an example. Here, the back gates of M _P and M _N are connected to power supplies V _WW and V _BB , respectively, and their back gate voltage values are changed between during operation and during standby. As for V _BB, the time zone in which high-speed operation is required by shallow V _BB (or in extreme cases slightly positively) that enable high-speed operation by reducing the V _T of M _N. The time zone requiring low power consumption by increasing the V _T of M _N to deepen the V _BB, suppress the subthreshold current. As a result, the effect (i) is further enhanced. Although V _BB has been described above, V _WW is the same _except that the polarity of the voltage is reversed. In addition, this type of back gate voltage generating circuit is, for example,
C.C., Digest of Technical Papers, pp.254-255, February 1985 (IS
SCCDigest of Technical Papers, pp.254-255, Feb.198
It is described in 5).

FIG. 9 is an example of a device structure for realizing the circuit of FIG. Here, the above-described triple well structure is used. The n-well 105 (the back gate of the P-channel MOS transistor) is connected to V _WW via the n + diffusion layer 120, and the p-well 103 (the back gate of the N-channel MOS transistor) is connected. V _BB via p + diffusion layer 127
It is connected to the. This triple well structure has the advantage that the back gate voltage can be set for each circuit because both the P-channel and the N-channel can be placed in independent wells for each circuit. For example, when a circuit in an operating state and a circuit in a standby state coexist in one LSI, the back gate voltage of the former can be made shallow and the back gate voltage of the latter can be made deep.

Next, the case of an inverter train in which inverters are connected in multiple stages will be described. For the sake of simplicity, the principle will first be described in the case of two stages. FIG. 10A is a circuit diagram when the CMOS inverters L ₁ and L ₂ are connected. For each inverter in each stage, switches S _Ci , S _Si and resistors R _Ci , R _Si
(I = 1, 2) is inserted. In high-speed operation mode, turn on all four switches, V _CC, to apply the V _SS directly to the inverter L _1, L _2. Inverter MOS
If the threshold voltage (V _T ) of the transistor is set low, high-speed operation can be achieved. On the other hand, in the low power consumption mode, all four switches are turned off, and power is supplied to the inverter through a resistor. Due to the voltage drop caused by the flow of the subthreshold current through the resistor, V _CL1 and V _CL2 fall below V _CC , and V _SL1 and V _SL2 rise above V _SS . The inverter L ₁ of the first stage, as in the case of FIG. 1, the subthreshold current decreases by a mechanism of the (i) (ii). However, FIG.
(B), the logical amplitude of the output N ₁ of L ₁ is smaller than the logical amplitude of the input signal IN. That is, when IN is at a low level (= V _SS ), the voltage level of N ₁ becomes V _CL1 ,
IN the voltage level of the N ₁ is at high level (= V _CC) is V
Becomes _SL1 . This because is the input of the inverter L ₂ of the second stage, for reducing the subthreshold current of L ₂ is
It is desirable to set the resistance value so that V _CC > V _CL1 > V _CL2 and V _SS <V _SL1 <V _SL2 . Accordingly, subthreshold current decreases by a mechanism of the (i) (ii) also L _2. When V _CL1 = V _CL2 and V _SL1 = V _SL2 ,
The effect of (i) is obtained, but the effect of (ii) is not obtained.

The same applies to the case of the multistage connection shown in FIG. 11A, where V _CC > V _CL1 > V _CL2 >...> V _CLk , V _SS <V
_SL1 <V _SL2 <...... <better to so as to be V _SLk.
However, as shown in FIG. 11B, since the logical amplitude becomes smaller for each stage, an appropriate level conversion circuit is inserted to recover the amplitude. In this example, a level conversion circuit LC is added after the k-stage inverter so that the logical amplitude of the output signal OUT becomes the same as that of the input signal IN. This type of level conversion circuit is described in, for example, Symposium on VSI Circuits, Digest of Technical Papers, pp. 82-83,
June 1992 (Symposium on VLSI Circuits, Digest
of Technical Papers, pp.82-83, June 1992). The level conversion circuit LC is unnecessary at the time of high-speed operation. Because all switches are on, V _CL1 = V _CL2 =... = V _CLk = V _CC , V _SL1 = V
_SL2 = ...... is a = V _SLk = V _SS, because there is no reduction in the logic amplitude. Therefore, during high-speed operation, the switch S
By turning on the _LC and bypassing the level conversion circuit, delays can be avoided.

FIG. 12A shows another example of a multistage connected inverter array. In this example, the switches S _C and S _S and the resistances R _C and R _S are shared by all the inverters L _{1 to} L _k, and the voltages V _CL and V _SL are common to L _{1 to} L _k . Therefore, as described in the description of FIG. 10, although the sub-threshold current reducing effect by the mechanism (i) is obtained,
The effect of i) cannot be obtained. Therefore, the effect of reducing the subthreshold current is smaller than that of the reference example. However, on the other hand, there is an advantage that the layout area of the switch and the resistor can be saved. Further, as shown in FIG. 12B, the voltage levels of all signals (including input / output signals) are the same, and there is a feature that the logic amplitude does not decrease as in the reference example. Therefore, there is an advantage that a level conversion circuit is not required and that logic such as NAND and NOR can be easily assembled.

Next, a case where the semiconductor integrated circuit to which the present invention is applied is applied to a general combinational logic circuit will be described.

For example, consider the combinational logic circuit shown in FIG. To apply a semiconductor integrated circuit to which the present invention is applied, first, logic gates are grouped as shown in FIG. In this example, 15 logic gates L _{1 to} L ₁₅ are 3
Are divided into _two groups G ₁ , G ₂ and G ₃ . In the grouping, the output signals of the logic gates included in the i-th group are input only to the logic gates of the (i + 1) -th and subsequent groups.

Next, as shown in FIG. 14, a switch and a resistor are inserted between each group and the power supply. The logic amplitude of the output signal of the logic gate is 1 as in the case of FIG.
Since the level becomes smaller for each stage, the level conversion circuit groups GC ₁ and GC ₂ are inserted as shown in FIG. 14 to recover the amplitude.
Although not shown, the level conversion circuit groups GC ₁ and GC ₂ may be bypassed during high-speed operation as in the case of FIG. One of the features of this embodiment is that the logic gates included in the same group share a switch and a resistor. In the example of FIG. 13, three inverters included in the group G ₁ is shared with the switch S _C1, S _S1 a resistor R _C1, R _S1. Another feature of the present embodiment is that the group before and after the level conversion circuit shares a switch and a resistor. That is, the groups G ₁ and G _{k + 1} include the switches S _C1 and S _S1 and the resistances R _C1 and R _S1 ,
Groups G ₂ and G _{k + 2} are comprised of switches S _C2 , S _S2 and resistor R
The _C2, R _S2, ......, a group G _k and G _2k are sharing switches S _Ck, S _Sk and resistor R _Ck, R _Sk, respectively. As described above, by sharing a switch and a resistor with a plurality of logic gates, the number of switches and resistors can be reduced as a whole LSI, and the layout area can be saved.

FIG. 15 shows another reference example of a semiconductor integrated circuit to which the present invention is applied. The reference example of FIG. 15 is different from the reference example so far, the voltage limiter (step-down circuit, a boosting _{circuit) VC 1, VC 2, ......} , VC k, VS 1, VS 2, ...
.., VS _k is used. When low power consumption is required, the switches T _{C1 to} T _Ck and T _{S1 to} T _Sk are switched to the illustrated side, and power is supplied to the logic gate group by the voltage limiter. Voltage limiter _{VC 1, VC 2, ......,} VC
_k is the power supply voltage V _CC side operates as a step-down circuit, the internal voltage V _CL1 that is substantially stabilized lower than V _CC, V _CL2, ...
.., V _CLk are generated. On the other hand, VS ₁ , VS ₂ ,
…, VS _k operates as a booster circuit on the ground _VSS side,
The internal voltage V _SL1 , which is almost stabilized higher than V _SS ,
V _SL2 ,..., V _SLk are respectively generated. The generated voltage is V _CC > V _CL1 > V _CL2 >...
It is _preferable that V _CLk , V _SS <V _SL1 <V _SL2 <... <V _SLk . Incidentally, this type of voltage limiter is disclosed in
It is disclosed in 246516. Conversely, when high-speed operation is required, the switches are switched to the opposite side to those shown in the figure, and V _cc and V _ss are applied directly to the logic gate group to enable high-speed operation. In this case, since the voltage limiter is not required, the operation may be stopped.

Although the reference example described so far is a circuit without feedback, such as an inverter array or a combinational logic circuit, the semiconductor integrated circuit to which the present invention is applied can be applied to a circuit with feedback. As an example, FIG.
The case of a latch circuit combining two NAND gates shown in FIG. FIG. 16B shows a circuit diagram. 2
NAND gates L ₁ and L ₂ , power supply Vcc and ground Vss
Between them, switches S _C1 , S _S1 , S _C2 , S _S2 and resistors R _C1 , R _S1 , R _C2 , R _S2 are inserted, respectively. V
_CL1, V _CL2 is lower than V _CC, V _SL1, V _SL2 rises than V _SS, the subthreshold current by a mechanism of (i) is reduced.

FIG. 17 shows four M bits used for latching information to further reduce the subthreshold current.
The threshold voltage V _T of the OS transistors M _P12 , M _P22 , M _N12 , M _N22 is changed to the other MOS transistors M _P11 , M _P21 ,
This is an example in which the threshold voltages of M _N11 and M _N21 are higher (more enhanced). Another MO to which the input signal is applied
Since the threshold voltages V _T of the S transistors M _P11 , M _P21 , M _N11 , and M _N21 remain low, high-speed operation is possible.
In this case, a switch and a resistor on the _VSS side are unnecessary. This is because the high threshold voltage V _SS side transistors M _N12 , M _N
This is because the current can be reliably suppressed by _N22 .

In the reference examples described above, the subthreshold current can be reduced regardless of whether the input signal is low or high. However, in an actual LSI, the time period during which the subthreshold current needs to be reduced, for example, the level of a specific signal in a standby state, is often known in advance. In such a case, the subthreshold current can be reduced with a simpler circuit.

FIG. 18 shows the input signal IN in the standby state.
Is a circuit example of an inverter array when it is known that the inverter row is at a low level (“L”). Since IN is low, nodes N ₁ , N ₃ , N ₅ ,... Are high, N ₂ , N ₄ , N ₆ ,
Are low, M _P2 , M _P4 ,... Of the P-channel MOS transistors are off, and M _N1 , M _N3 ,... Of the N-channel MOS transistors are off. The switches and resistors need only be inserted into the sources of these off transistors. The reason why the subthreshold current flows is that the transistor is in an off state.

As shown in FIG. 19, a switch and a resistor may be shared by a plurality of inverters. Although these reference examples have a restriction that the level of the input signal must be known, they have the advantage that the subthreshold current can be reduced with a simple circuit. FIG. 18, 1
As is clear from the comparison of FIG. 9 with FIG. 11, the number of switches and resistors is reduced, and a level conversion circuit becomes unnecessary. If the level of the input signal in the standby state is known not only for the inverter but also for the logic gates such as NAND and NOR, the subthreshold current can be reduced with a simpler circuit.

FIG. 20 shows an example of a two-input NAND gate, and FIG. 21 shows an example of a two-input NOR gate. Two input signals IN ₁
When IN and IN ₂ are both low level or both are high level, these gates are substantially equivalent to an inverter, so the method described in FIGS. 18 and 19 can be applied. The problem is when one input is low ("L") and the other input is high ("H") as shown.

In the case of the NAND gate of FIG. 20, although the P-channel MOS transistor M _P12 and the N-channel MOS transistor M _N11 are off, the output OUT is at a high level, so that the sub-threshold current flows through M.
_N11 . Therefore, a switch and a resistor may be inserted on the _VSS side. Conversely, in the case of the NOR gate of FIG. 21, it is the P-channel MOS transistor M _P14 through which the subthreshold current flows. Therefore, a switch and a resistor may be inserted on the V _CC side. 20 and 21 show examples in which the above method is applied to a two-input logic gate, but the same can be applied to a logic gate having three or more inputs. Also, the switch and the resistor may be shared with other logic gates.

[0051] Figure 22 is the clock inverter, the clock CLK ₁ in the standby state is a circuit example in which known to be low, CLK ₂ is at the high level. In this case, since both the MOS transistors M _P16 and M _N16 are off, the output OUT has a high impedance, and the voltage level of the output OUT is another circuit (not shown) connected to OUT.
Depends on Since the voltage level determines which of the MOS transistors M _P16 and M _N16 flows the subthreshold current, in this case, a switch and a resistor may be inserted on both the V _CC side and the V _SS side as shown in the figure. Also in the case of a general combinational logic circuit, if the level of the input signal is known in advance, the subthreshold current can be reduced with a simpler circuit. Description will be made by taking the combinational logic circuit shown in FIG. 13 as an example.

FIG. 23 shows an example of a circuit configuration in which all inputs IN _{1 to} IN ₆ of this circuit are known to be at low level.
Regarding the inverters L _{1 to} L ₃ , L ₅ and L ₆ , similarly to FIGS. 18 and 19, switches and resistors are inserted on the V _SS side of L _{1 to} L ₃ and the V _CC side of L ₅ and L _6. . NOR gate L _7, since both the input signal is low, is equivalent to a substantially inverter. Therefore, a switch and a resistor may be inserted on the _VSS side. NOR gate L ₄ are, one low-level input signal, since the other is high, as in FIG. 21, to insert a switch and resistor to V _CC side. Of the eight NAND gates in the circuit group G, only L ₁₂ is a three input signals are all high level, since an inverter equivalent, inserting a switch and a resistor shown in MC to V _CC side. In other NAND gates, a low level signal and a high level signal are mixed in the input signal.
A switch and a resistor indicated by MS may be inserted on the V _SS side. As is apparent from the above description, a switch and a resistor may be inserted on the V _SS side for a logic gate whose output is high and on the V _CC side for a logic gate whose output is low. As shown in FIG. 23, the layout area can be saved by sharing these switches and resistors with a plurality of logic gates.

FIG. 24 is a diagram showing an example of the layout configuration. This example is not disclosed elsewhere and is presented herein for the first time. A decoder circuit and a word driver circuit of a memory, particularly a dynamic random access memory (DRAM) are taken as an example. Groups G1 (decoder circuit) and G21 to G24 (word driver circuit) are shown in FIG.
G1 is a circuit group of the same kind as that of G, and MC1 is connected between the circuit group G1 and the power supply V _CC1 on the V _CC side, and between the circuit groups G21 to G24 and V _CC2 which is the power supply on the V _CC side. Has inserted MC2. MC1 and MC2 are pMO
S, and by the ON resistance and the OFF resistance of the pMOS,
The switches and resistors indicated by MC in FIG. 23 are realized.
That is, the ON resistance is the resistance when the switch is closed in FIG. 23, and the OFF resistance is the resistance when the switch is opened in FIG.
c. MA is a memory cell array in which memory cells MC are two-dimensionally spread, and when, for example, W1 is selected from the outputs W1 and W2 of the word driver circuit, the signal of the memory cell is read to the data line pair DT and DB. And amplified by the sense amplifiers SA1 and SA2. There are many such configurations in the DRAM, and the length of the MA in the horizontal direction in FIG. At this time, MC1 and MC2
1, are shared by G21 to G24, and are arranged in a region below the sense amplifier region in the drawing, as shown in FIG. With such an arrangement, the layout area can be saved.

If the signal level of a circuit having feedback is known in advance, the subthreshold current can be reduced by a simpler circuit. FIG.
5 is an example applied to the latch of FIG. This type of latch is usually operated in the standby state with the input signal IN
₁ and IN ₂ are both at a high level, and the output signals OUT ₁ and O 2
One of the UTs ₂ has a low level and the other has a high level, and holds one bit of information. FIG. 25 shows OUT ₁
There is a circuit configuration example when you know the low-level, OUT ₂ is at a high level. NAND gate L _1, since two input signals are both at a high level, an inverter equivalent, 18, similarly to FIG. 19, to insert a switch and resistor to V _CC side. NAND gate L _2, while the low level of the input signal, since the other is high, as in FIG. 20, may be inserted switch and resistor to V _SS side. Of course, these switches and resistors may be shared with other logic gates.

FIG. 26 shows an example in which the above method is applied to a well-known data output buffer such as a memory LSI. In the standby state, the output enable signal OE is the low level, the output is high level NAND gate L ₂₁ and L _22, an output of the inverter L ₂₃ is a low level. Therefore, the two MOS transistors M _P20 and M _N20 forming the output stage L ₂₄ are both off, and the output DOUT is high impedance. The logic gate L ₂₁ ~L _23, FIG. 23
In accordance with the policy described in the above description, a switch and a resistor may be inserted on the _VSS side or the _VCC side. The output stage L _24, similarly to the case of the clock inverter of Figure 22, may be inserted switch and resistor V _CC side, both V _SS side.

FIG. 27 shows an example in which the above method is applied to a well-known data input buffer such as a memory LSI. In the figure,
SB is a signal that goes high in the standby state. The output of the inverter L ₃₁ and L ₃₂ are, as shown in FIGS. 4 and 7, can be used to phi _S, switch control of the phi _C, respectively. L ₃₃ is a NAND gate whose inputs are the phi _S and the data input signal D _IN. Since φ _S is at the low level in the standby state, the output of L ₃₃ is at the high level regardless of D _IN , and the output of the output d _IN of the inverter L ₃₄ is at the low level. On the other hand, in the operating state, d _IN follows D _IN because SB is at a low level. For NAND gate L ₃₃ and the inverter L ₃₄ is
Each V _SS side, by inserting a switch and resistor to VCC side, can be reduced subthreshold current. But it can not be used this approach for inverter L ₃₁ and L _32,
The subthreshold current can be reduced by increasing the threshold voltage of the MOS transistor. Since switching between the standby state and the operating state does not often require a high speed, a MOS transistor having a high threshold voltage may be used. The reference examples of FIGS. 18 to 26 have the advantage that the sub-threshold current can be reduced with a simple circuit, but cannot be applied unless the signal level in the standby time is known, for example, during the time when the sub-threshold current reduction is required. There is. Therefore, at this time, it is desirable to determine the levels of as many nodes as possible in the LSI. By using the input buffer of FIG. 27, the level of the signal d _{IN at} this time can be determined to a low level. In addition, as a method for determining the level of the signal d _IN , for example, there is also a method of setting a specification that “the data input terminal D _IN is set to a low level (or a high level) in a standby state”. . The data input buffer has been described above, but the same applies to the input buffers for address signals and other signals.

FIGS. 18 to 27 show a memory LSI.
It is suitable to be applied to. This is because, in the memory LSI, there are relatively many nodes that are known to be at the high level or the low level in the standby state, and the levels of most nodes can be determined by using the input buffer of FIG. . 26 and 27 are LSIs.
It can be used not only as an input / output circuit for external terminals of the chip but also as a driver / receiver for an internal bus of a microprocessor, for example.

Although a reference example in which a semiconductor integrated circuit using the present invention is applied to a CMOS circuit has been described above, a semiconductor integrated circuit using the present invention has a unipolar MO.
The present invention can also be applied to a circuit including S transistors. FIG.
8 shows an example of a circuit composed of only N-channel MOS transistors. In the figure, PC is a precharge signal, I
N ₁ and IN ₂ are input signals. Standby, i.e. in the precharge state, PC is high, IN ₁ and IN ₂ are at a low level, the output OUT is precharged to a high level (= V _CC -V _T). In operation, after the PC becomes low level, IN ₁ and IN ₂ remains at or low level becomes the high level. If at least one of the IN ₁ and IN ₂ are at a high level, OUT goes low, if you stay in both low and OUT remains high. Namely, this circuit is a circuit for outputting the NOR of IN ₁ and IN _2. In this circuit, the transistors that are turned off during standby are M _N41 and M _N42 on the V _SS side, and a subthreshold current flows through these transistors. Therefore, to apply a semiconductor integrated circuit using the present invention to this circuit, a switch and a resistor may be inserted on the _VSS side as shown in the figure. It is not needed on the V _CC side.

The reference examples shown in FIGS. 18 to 28 have the advantage that the sub-threshold current can be reduced with a simple circuit, but are applicable when the sub-threshold current reduction is required, for example, when the signal level in the standby state is not known. There is a restriction that you can not. Therefore, at this time, L
It is desirable to determine the level of as many nodes as possible in the SI. As means for this purpose, the level of the signal d _{IN at} this time can be determined to be low by using a circuit such as the input buffer in FIG. As another method for determining this level, for example, there is also a method of setting a specification that “the data input terminal D _IN is set to a low level (or a high level) in a standby state”. The reference examples of FIGS. 18 to 28 are suitable for application to a memory LSI. Memory L
In the SI, there are relatively many nodes that are known to be at the high level or the low level in the standby state.
This is because the levels of most of the nodes can be determined by using the input buffer.

In the above example, there are problems that the logic amplitude decreases with an increase in the number of stages, and that if the voltage level of the input signal is not known in advance, a more complicated design is required. FIG. 29 solves these problems. In the time period required until the logical output is determined, the switch is turned on as described above to perform a normal high-speed operation.
In other time zones, the switch is turned off to cut off the subthreshold current path of the logic circuit (the example is a CMOS inverter). However, when the switch is turned off, the supply path of the power supply voltage is cut off, so that the output of the logic circuit becomes floating and the logic output is not determined. Therefore, a kind of latch circuit (level hold circuit) that holds the voltage level at its output
Is a feature. If a high threshold voltage transistor or the like is used for the level hold circuit, the subthreshold current of the level hold circuit can be reduced to a negligible level, and the subthreshold current can be reduced as a whole. The delay time is less affected by the level hold circuit and is determined by the logic circuit. Even if a high-speed circuit having a large driving capability is used for the logic circuit, current does not flow through the logic circuit in the standby state, so that the current consumption is only the current flowing through the level hold circuit. Since the level hold circuit only holds the output, the driving capability may be small, and the current consumption can be reduced. Even when the switch is turned off, the output of the logic circuit is held by the level hold circuit, so that there is no possibility that the output is inverted and the operation is stable. Therefore, a semiconductor device that performs stable operation at high speed with low power consumption can be realized. According to the semiconductor integrated circuit to which the present invention is applied, since the voltage level is always guaranteed to be a constant value by the level hold circuit, the logic amplitude does not decrease as the number of logic stages increases. In addition, it is effective regardless of the logic input. This reference example will be further described with reference to FIG. The logic circuit LC is connected to the high-potential power line VHH and the low-potential power line VLL via the switches SWH and SWL. Here, VHH and VLL can also correspond to V _CC and V _{SS described above} , respectively. A level hold circuit LH is connected to the output terminal OUT of the logic circuit LC. Switches SWH and SWL are
Controlled by the control pulse CK, they are turned on and off at the same time. The logic circuit LC includes logic gates and flip-flop circuits such as an inverter, a NAND circuit, and a NOR circuit, or a combination of a plurality of them. The level hold circuit LH can be constituted by a positive feedback circuit. The operation of the logic circuit LC is performed by turning on the switches SWH and SWL.
After the output OUT corresponding to the input IN of the logic circuit LC is determined, the switches SWH and SWL are turned off to cut off the current path from VHH to VSS via the logic circuit LC,
The output of the logic circuit LC is held by the level hold circuit LH. The circuit delay time includes a level hold circuit LH
Is small and is determined by the logic circuit LC. A high-speed operation with a short delay time can be performed by using a circuit having a large driving capability for the logic circuit LC. For example, in the standby state, no current flows through the logic circuit LC, and thus the consumption current is only the current flowing through the level hold circuit LH. Since the level holding circuit LH may have a small driving capability, the current consumption can be reduced. Moreover, since the output OUT of the logic circuit LC is maintained by the level hold circuit LH, there is no possibility of malfunction. Therefore, a circuit that performs stable operation at high speed with low power consumption can be realized.

A semiconductor integrated circuit to which the present invention is applied is a CMO
FIG. 30 shows a reference example constituted by S inverters. NM
OS transistor MN1, PMOS transistor MP1
Operate as switches SWL and SWH in FIG. 29, respectively. In order to reduce the leakage current when turned off, the threshold voltages of the transistors MN1 and MP1 are set sufficiently high. The channel width / channel length is determined so that the on-resistance does not increase. NMOS transistor MN1
And the control pulse CKB is input to the gate of the PMOS transistor MP1. C
KB is a complementary signal of CK. NMOS transistor M
A CMOS inverter INV consisting of N2 and PMOS transistor MP2 is connected to MN1 and MP1. To increase the driving capability at low voltage operation, the transistor MN
2. The threshold voltage of MP2 is reduced. Inverter I
The output terminal OUT of the NV is connected to the NMOS transistor MN.
3, MN4 and a level hold circuit LH composed of PMOS transistors MP3, MP4. In order to reduce the through current while holding the output, the threshold voltages of the transistors MN3, MN4, MP3, and MP4 are made sufficiently large, and the channel width / channel length is made sufficiently small.
Numerical examples of the power supply voltage and the threshold voltage will be described. VLL is set to the ground potential 0V, and VHH is set to the external power supply voltage 1V. N
The threshold voltage of the MOS transistor is MN2 of 0.2
V, MN1, MN3 and MN4 are set to 0.4V. PM
The threshold voltage of the OS transistor is as follows: MP2 is −0.2
V, MP1, MP3, and MP4 are -0.4V.

The operation will be described with reference to the timing chart shown in FIG. First, the control pulse CK is raised to VHH, and C
KB is lowered to VLL, transistors MN1 and MP1 are turned on, and the inverter INV is connected to VHH and VLL. When the input signal IN rises from VLL to VHH, MP2 turns off, MN2 turns on, and the output OUT
Is discharged from VHH to VLL. Transistor MN2
Starts conducting in the saturation region, and the value of the current flowing through MN2 is determined by the voltage between the gate (input terminal IN) and the source (node NL). Since the transistor MN1 is provided between the node NL and VLL, the potential of the node NL temporarily increases due to the on-resistance of MN1 and the current flowing from MN2. However, since the gate of MN1 is at VHH, the on-resistance can be designed to be sufficiently small even if the threshold voltage is large, and the effect on the delay time can be reduced. When the output OUT is inverted to VLL, the level hold circuit LH turns off MN4 and turns on MP4 so as to keep the output OUT at VHH. Therefore, when MN2 is turned on, a through current flows from VHH to VLL through MP4 and MN2. However, the effect on delay time and current consumption is small by designing the driving capability of MP4 smaller than that of MN2. When the output OUT falls, MN3 turns off and MN3 turns off.
P3 is turned on, and the node NL in the level hold circuit
H is inverted from VLL to VHH, MN4 turns on and MP4
Is turned off, and the level hold circuit LH outputs the output OUT.
Is maintained at VLL, and no through current flows. MP2 is off because both the gate and the source are VHH. However, since the threshold voltage is small, a large leak current flows through the inverter INV. Then, the control pulse CK is lowered to VLL, CKB is raised to VHH, the transistors MN1 and MP1 are turned off, and the inverter INV is separated from VHH and VLL. At this time, MN1 and MP1 are completely turned off because the gate and the source have the same potential and the threshold voltage is large. The output OUT is maintained at VHH by the positive feedback of the level hold circuit LH. At this time, since the NMOS transistor MN2 is on, the node NL is kept at VLL. On the other hand, node N
PMOS transistor MP2 from H to output terminal OUT
, The voltage of the node NH starts to decrease. Then, the source potential of MP2 falls below the gate potential and is completely turned off. As a result, the through current of the inverter INV does not flow in the standby state. Then, the input signal IN
Before the control signal changes, the control pulse CK is raised to VHH,
B is lowered to VLL, the transistors MN1 and MP1 are turned on, and the node NH is set to VHH. Input IN is VH
By inverting from H to VLL, the output OUT becomes VL
Invert from L to VHH. It is desirable that the level hold circuit LH quickly follow the output OUT so that the period during which a through current flows through the inverter INV and the level hold circuit LH is shortened. Therefore, the inverter IN
V and the level hold circuit LH are arranged close to each other to reduce wiring delay. As is apparent from this reference example, the threshold voltage of the MOS transistor used as a switch is
By setting the threshold voltage to about 0.4 V or more which is conventionally required to reduce the subthreshold current, the threshold voltage of the MOS transistor in the logic circuit can be reduced without increasing the through current in the standby state. it can. Even if the operating voltage is lowered to 1 V or less, the driving capability can be ensured by setting the threshold voltage of the MOS transistor to 0.25 V or less. Therefore, lower power consumption due to lower voltage can be realized. In addition, the performance can be improved by scaling the elements based on the conventional scaling rule. Moreover, since the configuration is the same as that of the conventional CMOS logic circuit except that a switch and a level hold circuit are loaded, the same design method as that of the conventional CMOS logic circuit can be used.

FIG. 32 shows a reference example in which the above method is applied to a CMOS inverter chain. An inverter chain can be realized by connecting the configuration in which two switches and a level hold circuit are also provided to the one-stage inverter shown in FIG. 30 in multiple stages. In this example, the number of elements and the area are reduced. Here, the case of a four-stage inverter chain is taken as an example, but the same applies to the case of other stages. Four inverters INV1, INV2, INV3,
INV4 is connected in series. Last stage inverter INV
4 is connected to the level hold circuit LH. Each of the inverters has a PM like the INV in FIG.
It is composed of one OS transistor and one NMOS transistor. The transistor size of each inverter may be the same or different. As is often used as a driver, the channel width is set to INV1, INV2, INV3, and INV between fixed stages with the same channel length.
It can be increased in the order of 4. The source of the PMOS transistor of each inverter is connected to node NH and NMO
The source of the S transistor is connected to node NL. Switch SW between node NL and low level power supply VLL
L is provided with a switch SWH between the node NH and the high-level power supply VHH. The switches SWL and SWH are controlled by a control pulse CK, and are turned on and off at the same time.
As shown in FIG. 30, the switch SWL is implemented by an NMOS transistor, and the switch SWH is implemented by a PMOS transistor whose gate receives a complementary signal of CK. The operation of the inverter chain is performed by turning on the switches SWL and SWH. For example, when the input IN changes from a low level VLL to a high level V
When inverted to HH, the node N is controlled by the inverter INV1.
1 is inverted from VHH to VLL, the node N2 is inverted from VLL to VHH by INV2, the node N3 is inverted from VHH to VLL by INV3, and the output terminal OUT is inverted from VLL to VHH by INV4. When OUT is determined to be VHH, the level hold circuit LH
At VHH. In the standby state, the switches SWL and SWH are turned off to cut off the current path from VHH to VLL via the inverter. When the above-described method is applied to an inverter chain, a level hold circuit may be provided only at an output terminal of the inverter chain by treating the inverter chain as one logic circuit as in the present embodiment. Also, switches SWL, SW
H can be shared by a plurality of inverters. Switch SWL,
The magnitude of SWH is determined by the magnitude of the flowing peak current. The peak of the sum of currents flowing through multiple inverters is
It becomes smaller than the sum of the peak current of each inverter. For example, when an inverter chain is configured with an interstage ratio of 3, the peak of the current sum is substantially equal to the peak current of the final stage. Therefore, when a switch is shared by a plurality of inverters, the area of the switch is smaller than when a switch is provided for each inverter.

FIG. 33 shows another reference example in which the above method is applied to an inverter chain. As in FIG.
Although the case of a stage inverter chain is taken as an example, the same applies to the case of other stages. Four inverters INV
1, INV2, INV3, and INV4 are connected in series.
Level hold circuits LH3 and LH4 are connected to a node N3 which is an output terminal of the inverter INV3 and an input terminal of the INV4 and an output terminal OUT of the INV4, respectively. Each inverter includes one PMOS transistor and one NMOS transistor, similarly to INV in FIG. The odd-numbered inverters INV1 and INV3 are connected to the nodes NL1 and NH1, respectively, and are connected to the even-numbered inverters INV2 and INV2.
INV4 is connected to nodes NL2 and NH2. Switches SWL1 and SWL2 are connected between nodes NL1 and NL2 and low-level power supply VLL, respectively.
Switches SWH1 and SWH2 are provided between H2 and the high-level power supply VHH, respectively. Switch SWL1,
SWL2 and SWH1 and SWH2 are controlled by a control pulse CK, and are turned on and off at the same time. The operation of the inverter is performed by the switches SWL1, SWL2, SWH1, SWH2.
Is turned on. For example, if the input IN is a low level VLL
From the high level to the high level VHH, the node N1
, The node N2 changes from VLL to VHH, the node N3 changes from VHH to VLL, and the output terminal OUT changes from VLL to VHH by INV4. N3 is VL
When it is determined to be L, the level hold circuit LH1 sets N3 to V
It operates to keep LL. When OUT is determined to be VHH, the level hold circuit LH operates to maintain OUT at VHH. For example, in the standby state, the switches SWL1, SWL2, SWH1, and SWH2 are turned off to cut off the current path from VHH to VLL via the inverter. At this time, since the node N3 is kept at the low level VLL by the level hold circuit LH3, the node NL1 is also VLL through the inverter INV3.
Is kept. Further, the node N1 is kept at VLL through the inverter INV1. Similarly, when the output terminal OUT is kept at the high level VHH by the level hold circuit LH4, the nodes NH2 and N2 are also kept at VHH. Therefore, the node connecting the inverters is V
It is kept at either HH or VLL. As described above, two sets of switches are provided, the odd-numbered inverter and the even-numbered inverter are connected to different switches, and one of the output terminals of the odd-numbered inverter and one of the output terminals of the even-numbered inverter is connected to To the nodes N1 and N1 between the inverters
2, N3 are all maintained at either a high level or a low level. Even if the standby state continues for a long time, the input of the inverter does not reach the intermediate level, so that the inverter operates stably, and there is no possibility that the information is inverted or a through current flows when the switch is turned on. The above method has been described with reference to a reference example in which the method is applied to a CMOS inverter or an inverter chain. However, the purpose of the method is to load a logic circuit with a switch and a level hold circuit to perform stable operation at high speed with low power consumption. The present invention is not limited to the reference examples described so far as long as they do not deviate from the above.

FIG. 34 shows another reference example in which the above method is applied to a CMOS inverter. In the reference example shown in FIG. 30, the transistor MN that operates as a switch
1 and MP2 to the CMOS inverter INV and the power supply VLL,
VHH. On the other hand, in this embodiment, it is provided between the NMOS transistor and the PMOS transistor. Two NMOS transistors MN2, MN1
And two PMOS transistors MP1 and MP2 are connected in series between a low-level power supply VLL and a high-level power supply VHH. NMOS transistors MN1 and PMOS
The transistor MP1 operates as a switch. In order to reduce the leakage current when turned off, the threshold voltages of the transistors MN1 and MP1 are increased. NMO
A control pulse CK is applied to the gate of the S transistor MN1.
A control pulse CKB of a complementary signal of CK is input to the gate of the PMOS transistor MP1. The gates of the NMOS transistor MN2 and the PMOS transistor MP2 are connected to the input terminal IN, and operate as a CMOS inverter. The threshold voltage of the transistors MN1 and MP1 is reduced in order to increase the driving capability in the low-voltage operation.
The output terminal OUT is connected to a level hold circuit LH configured in the same manner as in FIG. The operation is performed in the same manner as in the reference example shown in FIG. The transistors MN1 and MP1 are turned on by the control pulses CK and CKB, and the transistors MN2 and MP2 are operated as CMOS inverters. For example, when the input IN is inverted from the low level VLL to the high level VHH, the transistor MN2 which has been turned off starts to conduct and operates in the saturation region. At this time, the current value of MN2 is determined by the voltage between the gate and the source. In this reference example, the transistor MN1 is connected to MN2 and the output terminal O.
Since it is provided between the UT and the UT, the on-resistance of MN1 is connected to the drain of MN2. Therefore, the influence of the ON resistance of MN1 on the current value of MN2 is small. After the output OUT is determined, the transistors MN1 and MP1 are turned off to prevent a through current, and the output OUT is maintained by the level hold circuit LH. When a switch is inserted on the output terminal side of a logic circuit as in this reference example, the switch cannot be shared by a plurality of logic gates, but the influence of the ON resistance of the switch is small. When the same transistor is used as the switch, the delay time is shorter than when the switch is provided on the power supply side of the logic circuit as in the reference example shown in FIG. Alternatively, if the delay time is designed to be the same, the channel width / channel length of the transistor used as a switch can be reduced, and the area can be reduced.

FIG. 35 shows another configuration example of the level hold circuit. This level hold circuit is connected to the NMOS transistors MN3, MN4 and PMO in the reference example shown in FIG.
A case in which the level hold circuit LH configured by the S transistors MP3 and MP4 is used instead of the level hold circuit LH will be described. This level hold circuit has three N
MOS transistors MN3, MN4, MN5 and PMOS
It comprises transistors MP3, MP4 and MP5. In order to reduce the leakage current in the standby state, the threshold voltage of each transistor is increased. For example, an NMOS transistor is 0.4V, and a PMOS transistor is -0.4V.
And MN3 and MP3 constitute an inverter,
MN4, MN5, MP4, MP5 constitute a switching inverter. The control pulse C is applied to the gate of MN5.
Control pulse CK is inputted to the gate of KB and MP5. The operation timing is the same as that in the case where the level hold circuit LH shown in FIG. 30 is used, and is as shown in FIG. The control pulse CK is raised to a high level VHH and CK
B is lowered to the low level VLL to operate the inverter INV. At this time, the transistor M
N5 and MP5 are turned off. Therefore, when the output OUT is inverted, no through current flows through the inverter INV and the level hold circuit, and the delay time and the current consumption can be reduced. In the standby state, the control pulse CK is lowered to the low level VLL, the CKB is raised to the high level VHH, and the inverter INV is disconnected from the power supplies VLL and VHH. At this time, in the level hold circuit, the transistor MN
5, MP5 is turned on, and the output OUT is held by positive feedback.

As described above, by configuring the level hold circuit with the combination of the inverter and the switching inverter, the number of transistors increases by two. However, the logic circuit and the level hold circuit do not compete with each other, and the delay time and current consumption are reduced. I can do it. In addition, the driving capability of the level hold circuit may be increased, and stable operation can be performed without a possibility that the output fluctuates even when the leakage at the output terminal is large. As described above, in recent microprocessors operating from 3.3 V to 5 V, in order to reduce power consumption, application of a clock to circuits unnecessary in a low power backup mode (sleep mode) or the like is stopped to charge and discharge current. Or to reduce. In this reference example, as shown in FIG.
By setting both the clocks CK1t and CK2t to the low level during the sleep mode, the transistors MP11 and MN11, MP12 and MN12 are all turned off, and the through current of both the logic circuits LC1 and LC2 is cut off. Therefore, the effect of reducing the sub-threshold current is greater in the sleep mode than in the operation mode. In the reference examples of FIGS. 29 to 35, the power switch is controlled by one timing signal CK (CKB). However, when there are a plurality of circuit blocks in the LSI, each power switch is controlled at a different timing. Thereby, the subthreshold current can be further reduced. FIGS. 36 to 39 illustrate this method as an embodiment of the present invention.
Shown in The following method can be used not only for reducing the subthreshold current but also for reducing the current during general non-transient operation.

Embodiment 1 FIG. 36 is an example showing a control example of power switches of a plurality of circuit blocks according to a first embodiment of the present invention. IN represents a signal input to the LSI chip as a representative, and during the operation period, the signals of IN and LG1, L
The logic circuit blocks following G2 and LG3 operate one after another. Each logic circuit block includes a logic circuit LC and a level hold circuit LH as described with reference to FIGS. SWH1 to SWH3 are VCC and LG1, LG2,
This is a power switch inserted between the switch SW3 and LG3.
SWL3 are power switches inserted between VSS and LG1, LG2, LG3. The feature of FIG.
The power switches SWH1 and SWL1 are controlled by the sleep mode / normal operation mode switching signal SLP, and the power switches SWH2 to SWL of the subsequent stages LG2 and LG3 are detected by means KH1 to KH3 for sensing the operation of the preceding stage.
3 is performed. Although not shown in the drawings, means for detecting the operation at the subsequent stage and turning off the power switch of each logic circuit block, or having a timer and automatically turning off the power switch after a predetermined time may be provided. Even if the power switch is turned off, the information is held by the level hold circuit in each logic circuit block. Since the power switch of each logic circuit block is turned on for the first time when the logic circuit block operates, the sub-threshold current of the entire LSI decreases. Also, the transition from the sleep mode to the normal operation mode requires only a short time since only the first stage needs to be reset (set). In the figure, KH1 detects an output change of LC in LG1.
A change in an internal node of C may be detected. Also, KH1
Thus, not only the power switch of the next-stage LG2 may be activated, but also the power switch of the LG3 of the subsequent stage may be activated.

FIG. 37 shows an operation example of FIG. This is an example in which the sleep mode is when the SLP is at a high level, and the operation mode is when the SLP is at a low level. By the way, at time t1, the SLP switches from the high level to the low level, and switches from the sleep state to the normal operation state. Thereby, the first stage LG1
Power switches SWH1 and SWL1 are turned on. Next, at time t2, IN changes and LG1 operates. The time period t2 to t1 is short because only the SWH1 and SWL1 need to be turned on as described above. Note that this SWH
1, SWL1 is always active while SLP is at a low level. On the other hand, the other power switches of corresponding circuit blocks are turned on along the signal flow. That is, at time t3, the output φG1 of LG1 is switched, KH1 detects this, and switches φ1 to turn on the power switches SWH2, SWL2 of LG2 of the next stage. As a result, LG2 operates and its output φG2 switches at time t4. Further, KH2 detects this change, switches φ2, and turns on power switches SWH3 and SWL3 of LG3. As a result, the LG3 operates. Here, time t
If φG2 is switched at 4 and LG3 at the subsequent stage starts operating, it is only necessary that LG2 keep its output level. Therefore, φ1 is switched again at time t5, and the power switch can be turned off. The detection at the time t5 may be fed back from the output of the subsequent circuit as described above, or a timer may be provided. Hereinafter, a similar operation is performed.

Embodiment 2 FIG. 38 is a diagram showing a control example of a power switch in an LSI which operates in synchronization with a clock according to a second embodiment of the present invention. In this example, the LSI chip of interest operates in synchronization with the clock signal CLK, and one operation of this LSI is completed by a clock of n cycles (here, n = 4). In the chip, circuit blocks LG1 to LG4 receive input IN in synchronization with CLK.
Work in order. Each circuit block comprises a logic circuit and a level hold circuit as in the previous reference example. The feature of this example resides in that the power line switch control circuit SV controls the power line switches SWH1 to SWL4 by using the CLK to suppress the subthreshold current. Since each circuit block operates only one cycle out of n cycles, the power supply line switches may be sequentially turned on and off in accordance with the signal flow inside the chip. As a result, the number of circuit blocks in which the power switch is activated can be reduced to about 1 / n.

FIG. 39 shows an operation example of FIG. This is an example in which one cycle of the LSI chip operates with four clocks of CLK. In response to the falling edge of CLK in the first cycle,
The signal of IN at that time is taken in, φ1 is switched and SW
H1 and SWL1 are turned on, and LG1 operates. Before and after the output φG1 of LG1 is switched (slightly before in the figure), φ2 is switched in response to the next fall of CLK, SWH2 and SWL2 are turned on, and LG2 becomes operable. When φG1 is switched and the operation of LG2 starts, it is only necessary to keep the output level in LG1. Therefore, SWH1 and SWL1 are turned off at an appropriate timing (here, the next rising edge of CLK), and the signal is held by the level hold circuit in LG1. Hereinafter, the power switch is controlled as shown up to φ4.
As a result, in each circuit block in the LSI chip,
Since the power supply line switch can be turned on and off frequently by CLK, an operation with low current consumption including a subthreshold current can be performed.

In a random logic LSI or the like such as a microprocessor, the output of an internal register is fixed, or a logic such as a flip-flop circuit with a reset function is added to forcibly fix the voltage of a problematic node. It is also effective to do so. FIG. 40 shows a configuration example of a latch circuit capable of fixing an output. This circuit has a simple configuration in which an inverter in a normal latch circuit is replaced with a NAND circuit. As shown in FIG. 41, while φ _S is at a high level, the circuit operates as a normal latch circuit, and while φ _S is at a low level (sleep mode), the level of the output signal Q is fixed at a high level. Here, the sleep mode is a mode in which the operation of the entire LSI or a unit of a circuit block is stopped in order to reduce current consumption. If φt is set to a low level and φb is set to a high level during the sleep mode, the subthreshold current of the latch circuit itself can be reduced. When using the latch circuits, phi _S is because the node N ₄₁ by becoming to the low level is forced to high level, the information of the register is cleared by the sleep mode. However, there is no problem in a method of saving necessary information in the CPU to the main memory and resuming from the reset state after the sleep mode, for example, a resume function for setting a notebook computer to a standby state when there is no input for a predetermined time. . FIG. 42 shows another configuration example of the latch circuit that can forcibly fix the output. As shown in FIG. 43, this circuit also has φ
_S is between the high level and operates a normal latch circuit, while phi _S is at low level to determine the level of the output signal Q to the high level. The latch circuit, phi _{because S} does not affect the node N ₄₁ be in a low level, can hold also information during the sleep mode. After the sleep mode is released, the sleep mode can be resumed from the state before the sleep mode, and the sleep mode can be set even while the CPU is executing the task. Therefore, it is suitable when returning from the sleep mode in a relatively short time. In an LSI or the like that performs a complicated operation such as a random logic LSI, for example, the logic (voltage) state of each node inside the chip in a standby state is obtained by using the design automation (DA) method, and the result is obtained. Accordingly, the position where the above-described switch and resistor are inserted can be automatically determined by DA. The reference examples of FIGS. 18 to 27 assume that the input signal is at a specific level. If the input level is different from the intended level, the effect of reducing the subthreshold current is reduced. Therefore, for example, when the power is turned on, the input signal level is not determined, and a large subthreshold current may flow. To prevent this, it is desirable to switch on the power supply line as shown in FIGS. 44 to 48 as an embodiment of the present invention.

Embodiment 3 FIG. 44 is a diagram showing a first control example of the power line switch according to the third embodiment of the present invention. K1 is, for example, as shown in FIG.
28 is a group of logic gates shown in FIGS. The power line switch SCC is controlled by the control circuit SV. This circuit includes a level detection circuit LD1 for detecting the level of the externally applied power supply VCC and a level detection circuit LD2 for detecting the level of the external input signal IN, and these circuits generate output signals φVC and φSB, respectively. . LL is φVC
And a logic circuit that receives the signal φSB and generates a switch control signal φ1. That is, at the time of rising of VCC, it is detected that VCC has reached a predetermined level and the input signal IN has reached a specific level (a level for reducing the sub-threshold current of K1), and the switch SCC is turned on. At the time of the fall, the switch is turned off by detecting a decrease in the level of VCC.

FIG. 45 shows an operation example of the LSI shown in FIG.
When the power supply VCC is turned on, the potential rises. When the potential reaches, for example, VCα, the LD1 operates, and in this example, the output signal φVC is switched from a low level to a high level. Next, when the input signal IN becomes a specific signal level (here, a high level) in which the sub-threshold current reduction effect of K1 is large, when the level becomes VCβ or more in the example of this figure, the output φSB of the LD2 switches. This allows φ1
Is switched and the power switch is turned on.
C1 stands up. Conversely, when IN rises before VCC, first, when IN rises above VCβ, LD2
Is switched, and thereafter, when VCC reaches VCα, LD1 operates to switch φVC from a low level to a high level. As a result, φ1 switches, the power switch is turned on, and the internal power supply VC1 rises. In any case, since the switch is turned on after the level of IN is determined, a large subthreshold current does not flow. LL becomes IN after VCC becomes VCα or more.
Is changed so that φ1 does not change even if φSB changes. Internal power supply VC1 is external power supply VCC
Falls by falling. Although the switch is placed on the VCC side in the example of this figure, it may be placed on the VSS side. In some cases, a plurality of power supplies are applied. In that case, a level detection circuit may be provided for at least one of the power supplies.

Embodiment 4 FIG. 46 is a diagram showing a second control example of the power line switch according to the fourth embodiment of the present invention. The features of this embodiment are:
That is, a circuit LK1 (here, NOR gate) for determining the input signal level of the logic gate group K1 is provided. With this circuit, when the power supply rises, K1
Of the input signal IN ′ is fixed to a level (here, a low level) for reducing the subthreshold current of K1. FIG. 47 shows an operation example. When the power supply VCC is turned on and reaches a predetermined potential level VCα, the LD1 detects this and switches the signal φVC from a low level to a high level in this example. Thereby, the one-shot generation circuit OSH
As a result, a one-shot pulse is generated in φK1. When φK1 goes high, the input signal I of K1
N ′ is independent of the level of the input signal IN from the outside.
Becomes low level. In parallel, φ
VC generates φVC ′, the switch SCC is turned on, the internal power supply VC1 rises, and current is supplied to K1. Already due to the above-mentioned LK1, IN 'has become a level for reducing the subthreshold current of K1.
This prevents a large current from flowing when the power is turned on without determining the internal potential. When VCC falls,
As a result, the internal power supply VC1 also falls. In FIG. 46, only the level detection circuit for VCC is shown. However, as shown in FIG. 44, a level detection circuit for input signal IN or another power supply may be provided. Although the switch is placed on the VCC side in the example of this figure, the switch is connected to the VSS.
You can put it on the side.

Fifth Embodiment FIG. 48 is a diagram showing a third control example of the power line switch according to the fifth embodiment of the present invention. In the embodiments shown in FIGS. 44 to 47, the power supply line switch control circuit SV receives the external power supply VCC, uses it as a power supply for the circuit, and detects this level. However, in this embodiment, L
A battery other than the external power supply VCC is provided on the SI board, and the battery supplies the power VCT to the SV. For example, only one battery is provided on the board, and this may be shared by a plurality of chips. With such a configuration, even when the power supply VCC is not turned on, the change in the original power supply VCC can be easily monitored because the level detection circuit operates. Each LSI chip may have the same configuration as that of FIG. 44 or FIG. However, the power supply line switch control circuit SV is always activated by the current from the battery, and a change in the external power supply VCC is monitored. With this configuration, it is possible to easily prevent the excessive subthreshold current at the time of power-on described above. FIG.
4, a battery that can always obtain a constant voltage is used. However, if a power source whose level is determined first is prepared, this can be used instead of the battery.

As described above, the present invention is extremely effective in reducing the power consumption of a MOS transistor circuit and a semiconductor integrated circuit constituted by the MOS transistor circuit. The demand for lower power consumption of semiconductor integrated circuits has been particularly strong recently. For example, Nikkei Electronics, September 2, 1991, No. 106
Pages 111 to 111 describe a microprocessor system having a low power backup mode. In the backup mode, the clock is stopped or the supply of power to unnecessary parts is stopped to reduce power consumption. However, no consideration has been given to reducing the subthreshold current. The subthreshold current is small enough to be problematic because these processor systems operate at 3.3-5V and use transistors with sufficiently high threshold voltages. However, the operating voltage will be reduced to 2V or 1.5V in the future,
When the threshold voltage must be lowered, the conventional CMO
With the use of the S circuit, the excessive subthreshold current can no longer be reduced. If the present invention is applied to, for example, a resume circuit (power is supplied even in the backup mode), further reduction in power consumption can be realized.

[0078]

As described above, according to the present invention,
A high-speed and low-power-consumption MOS transistor circuit and a semiconductor integrated circuit constituted by the MOS transistor circuit can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing an inverter according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating the principle of sub-threshold current reduction according to the present invention.

FIG. 3 is a diagram showing a sub-threshold current reducing effect according to the present invention.

FIG. 4 is a circuit diagram of an inverter according to a second embodiment of the present invention.

FIG. 5 is a diagram showing signal timings of the present invention.

FIG. 6 is a diagram showing a device structure of the present invention.

FIG. 7 is a circuit diagram of an inverter according to a third embodiment of the present invention.

FIG. 8 is a circuit diagram of an inverter according to a fourth embodiment of the present invention.

FIG. 9 is a diagram showing a device structure of the present invention.

FIG. 10 is a diagram showing an inverter array according to a fifth embodiment of the present invention.

FIG. 11 is a diagram showing an inverter array according to Embodiment 6 of the present invention.

FIG. 12 is a diagram showing an inverter array according to a seventh embodiment of the present invention.

FIG. 13 is a diagram showing an example of grouping of combinational logic circuits to which the present invention is applied;

FIG. 14 is a diagram showing a combinational logic circuit according to Embodiment 8 of the present invention.

FIG. 15 is a diagram showing a combinational logic circuit according to Embodiment 9 of the present invention.

FIG. 16 is a diagram showing a latch according to a tenth embodiment of the present invention.

FIG. 17 is a circuit diagram of a latch according to Embodiment 11 of the present invention;

FIG. 18 is a circuit diagram of an inverter array according to a twelfth embodiment of the present invention.

FIG. 19 is a circuit diagram of an inverter array according to Embodiment 13 of the present invention.

FIG. 20 is a circuit diagram of a NAND gate according to Embodiment 14 of the present invention;

FIG. 21 is a circuit diagram of a NOR gate according to Embodiment 15 of the present invention.

FIG. 22 is a circuit diagram of a clock inverter according to Embodiment 16 of the present invention.

FIG. 23 is a circuit diagram of a combinational logic circuit according to Embodiment 17 of the present invention;

FIG. 24 is a layout example of a combinational logic circuit according to Embodiment 17 of the present invention;

FIG. 25 is a circuit diagram of a latch according to Embodiment 18 of the present invention;

FIG. 26 is a circuit diagram of an output buffer according to Embodiment 19 of the present invention;

FIG. 27 is a circuit diagram of an input buffer according to a twentieth embodiment of the present invention.

FIG. 28 is a circuit diagram of an NMOS dynamic circuit according to Embodiment 21 of the present invention.

FIG. 29 is a diagram showing a conceptual reference example.

FIG. 30 is a circuit diagram of a reference example applied to a CMOS inverter.

FIG. 31 is an operation timing chart of a reference example applied to a CMOS inverter.

FIG. 32 is a diagram showing a reference example applied to an inverter chain.

FIG. 33 is a diagram showing another reference example applied to an inverter chain.

FIG. 34 is a diagram showing another reference example applied to a CMOS inverter.

FIG. 35 is a circuit diagram of another configuration example of the level hold circuit.

FIG. 36 is a diagram illustrating a power switch control example of a plurality of circuit blocks according to the first embodiment of the present invention.

FIG. 37 is a diagram showing an operation example of FIG. 36;

FIG. 38 is a diagram showing an example of power switch control in clock synchronous operation according to the second embodiment of the present invention.

FIG. 39 is a diagram showing an operation example of FIG. 38;

FIG. 40 is a circuit diagram of a latch circuit capable of fixing an output.

FIG. 41 is an operation timing chart of a control clock.

FIG. 42 is a circuit diagram of another latch circuit capable of fixing an output.

FIG. 43 is an operation timing chart of a control clock.

FIG. 44 is a diagram illustrating a first control example of the power line switch according to the third embodiment of the present invention.

FIG. 45 is a diagram illustrating an operation example of the example in FIG. 44;

FIG. 46 is a diagram illustrating a second control example of the power line switch according to the fourth embodiment of the present invention.

FIG. 47 is a diagram illustrating an operation example of the example in FIG. 46;

FIG. 48 is a diagram illustrating a third control example of the power line switch according to the fifth embodiment of the present invention.

FIG. 49 is a circuit diagram of a conventional CMOS inverter.

FIG. 50 is a diagram showing a sub-threshold characteristic of a MOS transistor.

[Explanation of symbols]

L, L _{1 to} L _k ... Logic gates, G _{1 to} G _k ... Logic gate groups, S _C , S _{C1 to} S _Ck , S _S , S _{S1 to} S _Sk .
R _C , R _{C1 to} R _Ck , R _S , R _{S1 to} R _Sk ...

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ryoichi Kurihara 810 Shimo-Imaizumi, Ebina-shi, Kanagawa Prefecture Within the Office Systems Division, Hitachi, Ltd. Inside Hitachi Central Research Laboratory (72) Inventor Masakazu Aoki 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside Hitachi Central Research Laboratories Co., Ltd. In-house (58) Field surveyed (Int. Cl. ⁷ , DB name) H03K 19/0948

Claims (11)

(57) [Claims] 1. A circuit block including a logic gate, and a control circuit connected between a first node and a first operating potential point, wherein the logic gate is connected to the first node and the second node. A first MOSFET having a source-drain path between the first and second nodes, wherein the control circuit receives a control signal, and when the control signal is in a first state, a first current flows between the first node and the second node. And when the control signal is in the second state, the current flowing between the first node and the second node is limited to a current smaller than the current value of the first current. A semiconductor integrated circuit wherein the control signal switches from the second state to the first state after the potential at the first operating potential point exceeds the first potential when the potential at the point rises. 2. The potential difference between the first potential and the second node is large enough to drive the logic gate, the first operating potential point is connected to a first power supply line, and the first operating potential is 2. The semiconductor integrated circuit according to claim 1, wherein the time when the voltage at the point rises is when the power is turned on. 3. A circuit block including a logic gate, a control circuit connected between a first node and a first operating potential point, and a detecting circuit for detecting the potential at the first operating potential point. Wherein the logic gate includes a first MOSFET having a source / drain path between the first node and the second node; the control circuit receives a control signal; and when the control signal is in the first state, A first current is allowed to flow between one node and the second node, and when the control signal is in the second state, a current flowing between the first node and the second node is changed to the first current. And when the potential of the first operating potential point rises and the potential of the first operating potential point detected by the detection circuit becomes higher than the first potential, the control signal is From the second state to the first The semiconductor integrated circuit, wherein the switching to state. 4. A first input signal received by said logic gate,
4. The semiconductor integrated circuit according to claim 3, wherein the potential of the first operating potential point detected by the detection circuit changes after the potential becomes higher than the first potential. 5. The semiconductor integrated circuit according to claim 3, wherein an operation voltage of said detection circuit is supplied from a terminal connected to a battery. 6. A circuit block including a plurality of logic gates, a control circuit connected between a first node and a first operating potential point, and a detecting circuit for detecting the potential at the first operating potential point. Wherein each of the logic gates comprises a first MOSFET having a source-drain path between the first and second nodes, and one of the logic gates in the circuit block receives a first input signal. The control circuit receives a control signal, and allows the first current to flow between the first node and the second node when the control signal is in the first state; Sometimes, the current flowing between the first node and the second node is limited to a second current having a current value smaller than the first current, and when the potential at the first operating potential point rises, the detection circuit The first detected by The semiconductor integrated circuit in which the potential of the work potential point the control signal by which is greater than the first potential, characterized in that the switch to the first state from said second state. 7. The semiconductor integrated circuit according to claim 6, wherein the operation voltage of said detection circuit is supplied from a second supply source different from the first supply source for supplying a potential at a first operation potential point. 8. The semiconductor integrated circuit according to claim 7, wherein said second supply source is supplied from a terminal connected to a battery. 9. A first MOS transistor having a source / drain path connected in series with a source / drain path of the first MOS transistor between a first potential point and a second potential point. A MOS transistor, wherein the source of the first MOS transistor is
A MOS transistor circuit configured to obtain an output signal from an output node that is a common connection point between a drain path and the source / drain path of the second MOS transistor; and at least one of the first and second MOS transistors And control circuit means to which a control signal is supplied, and detection means to detect a change in an operating voltage supplied to the MOS transistor circuit. Setting to the state of 1 allows a relatively large current to flow through the source of the one transistor,
The control signal supplied to the control circuit means is transmitted to the first
By setting the second state different from the state described above, the current flowing to the source of the one transistor is limited to a value smaller than the relatively large current, and the detecting means determines that the operating voltage has exceeded the first value. A semiconductor integrated circuit that changes the control signal from the second state to the first state in response to the control signal. 10. The semiconductor integrated circuit according to claim 9, wherein a power supply voltage is applied to said detecting means from a battery. 11. A semiconductor integrated circuit comprising a plurality of semiconductor integrated circuits according to claim 10, wherein said battery is shared by said plurality of semiconductor integrated circuits and a power supply voltage is applied to said means of said plurality of semiconductor integrated circuits. .