KR100363769B1 - Semiconductor integrated circuit device - Google Patents

Abstract

PURPOSE: Provide is a semiconductor integrated circuit capable of operating at high speed and with low power consumption even when the size of MOS transistors is scaled down. CONSTITUTION: Switches(SCi,SSi) and resistances(RCi,RSi) are provided for each inverter at every stage. In the high speed operation mode, all four switches are switched on, and VCC and VSS are applied directly to inverters(L1,L2). High-speed operation is made possible by setting the threshold voltages of the MOS transistors of the inverters low. On the other hand, in the low power consumption mode, all of the switches are switched off, and the power is supplied to the inverters through resistances. Voltages(VCL1,VCL2) fall lower than VCC, and voltages(VSL1,VSL2) rise higher than VSS by voltage drops due to the fact that the subthreshold current flows through the resistances.

Description

Semiconductor integrated circuit device {SEMICONDUCTOR INTEGRATED CIRCUIT DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit device composed of fine MOS transistors, in particular a circuit suitable for high speed and low power operation, and an electronic device using the same.

As the MOS transistor is manufactured in a small size, as described in the International Symposium on VLSI Technology Systems and Applications, pages 188-192 (published May 5, 1989) in 1989, its breakdown voltage Will be lowered. Therefore, the operating voltage must also be lowered. In particular, the operating voltage must be lowered to achieve low power consumption in semiconductors used in battery operated portable devices and the like.

An object of the present invention is to provide a semiconductor integrated circuit capable of operating at high speed and low power consumption even if the semiconductor integrated circuit is miniaturized.

Still another object of the present invention is to provide a semiconductor integrated circuit capable of operating at high speed and low power consumption suitable for driving a battery even if a semiconductor integrated circuit is miniaturized.

In such a case, in order to maintain the high speed operation, it is necessary to lower the threshold voltage V _T of the MOS transistor in response to the decrease in the operating voltage. This is because the operating speed depends on the effective gate voltage of the MOS transistor, that is, the value obtained by subtracting V _T from the operating voltage, and the larger this value, the higher the speed.

For example, a typical value of the threshold voltage of a transistor operating at 1.5V and having a channel length of 0.25 mu m is expected to be 0.35V according to the above description. According to the known reduction method, the typical value of the threshold voltage is about 0.24V assuming that the operating voltage of the transistor is 1V. However, if the threshold voltage (V _T ) falls below 0.4 V, this does not allow the transistor to be turned off completely, and as described later, the subthreshold characteristics (tailing) of the MOS transistors. Characteristic), the DC current starts to flow through the transistor. Thus, this current has actually become a serious problem when operating at 1.5V or less.

Referring to the conventional CMOS inverter shown in Fig. 35, ideally, when the input signal IN is at the low level (= V _SS ), the N-channel MOS transistor M _N is turned off and the input signal is at the high level ( = V _CC ), the P-channel MOS transistor M _P is turned off so that no current flows in any case. However, when the threshold voltage V _T of the MOS transistor is lowered, the sub threshold current cannot be ignored. As shown in FIG. 36, the drain current I _DS in the sub-threshold region is proportional to the exponential function of the gate-source voltage V _GS and is represented by the following equation.

Here, W denotes the channel width of the MOS transistor, I ₀ and W ₀ denote the current value and the channel width when the threshold voltage V _T is defined, and S denotes the sub threshold amplitude (the current decreases by 10 times). Gate-voltage amplitude). Thus, the threshold current I _{L represented} by

It also flows when V _GS = 0.

The threshold current (I _L) of the above-described since V _GS = 0 from the transistors in the OFF state of the CMOS inverter shown in Figure 35 is the ground potential at the time of non-operation in the high-power voltage (V _CC) at the time of non-operation low-power It will flow with voltage V _SS .

The dressy and hold current is a 36 V _T increases exponentially with "dressy I _L I _L from when the threshold voltage is lowered to" at V _T, as shown in. As is clear from Equation (2), in order to reduce the subthreshold current, S may be decreased or V _T may be increased. However, the former lowers the speed by lowering the effective gate voltage. In particular, when the operating voltage is lowered as the breakdown voltage breakdown is reduced in view of the breakdown voltage, the speed decrease becomes remarkable, and the advantages of the microstructure manufacturing are already lost, which is undesirable.

The latter is also difficult to apply as long as operation is assumed at room temperature for the following reasons.

The sub-threshold amplitude S is represented by the capacitance C _OX of the gate insulator and the capacitance C _{D of the} depletion layer under the gate as follows.

Where K is the Boltzmann constant, T is the absolute temperature, and q is the body charge.

As can be seen from the above formula, S ≧ KT ln 10 / q irrespective of C _OX and C _D , so it is difficult to be 60 mV or less indoors.

The actual direct current of a semiconductor integrated circuit composed of a plurality of MOS transistors is markedly increased by the above-described phenomenon. That is, when the operating voltage is lowered at a constant operating speed, the threshold voltage V _T is also lowered, thereby causing a more serious condition than when the operation is performed at low voltage. In particular, when operating at high temperatures, V _T is low and S is high. Therefore, this problem becomes more serious. Low power consumption is important in the downsizing of future computers and the like, and an increase in the subthreshold current becomes an inherent problem. In particular, in electronic devices where it is desired to operate from 0.9V to 1.6V by one cell, it is also very important to cope with the increase of current.

In order to solve the above-mentioned problems, according to the present invention, the control circuit means for controlling the large and small current supply is inserted between the source and the power supply of the MOS transistor so that these currents are switched according to the purpose of use. do. For example, a large current is supplied when a high speed operation is required, and a small current is supplied when a low power consumption is required.

Since high speed operation is required in normal operation, a large current is supplied from the current supply means to the MOS transistor circuit to enable the high speed operation. At this time, however, as described above, the direct current flows into the MOS transistor circuit, but this current is usually very small compared to 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 supply current is changed to a small current to suppress the sub-threshold current. In this case, the logic voltage swing of the MOS transistor circuit is generally smaller than that at the time of supplying a large current due to the limitation of the current, but it is not a problem as long as the logic level can be guaranteed.

As described above, low power consumption and high speed can be realized by using the semiconductor integrated circuit device and the MOS transistor circuit having the same configuration as the present invention.

In addition, although the MOS semiconductor integrated circuit device is described as an example in the present invention, it is generally applicable to a metal insulator semiconductor (MIS) integrated circuit.

1A is a diagram showing an inverter in Embodiment 1 of the present invention, (b) is a diagram showing a voltage level of a signal of one inverter in Embodiment 1,

2 is a view showing the principle of sub-threshold current reduction according to the present invention;

3 is a view showing an effect of reducing a subthreshold current according to the present invention;

4 is a circuit diagram showing an inverter in Embodiment 2 of the present invention;

5 (a) to 5 (c) show the signal timing of the present invention;

6 shows the structure of the device of the invention,

7 is a circuit diagram of an inverter in Embodiment 3 of the present invention;

8 is a circuit diagram of an inverter in Embodiment 4 of the present invention;

9 shows the structure of the apparatus of the present invention,

(A) is a view showing the inverter string in the fifth embodiment of the present invention, (b) is a view showing the voltage level of the signal of the inverter string in the fifth embodiment,

11 (a) is a view showing an inverter string in the sixth embodiment of the present invention, (b) is a view showing a voltage level of the inverter column signal in the sixth embodiment,

12 (a) is a view showing the inverter string in the seventh embodiment of the present invention, (b) is a view showing the voltage level of the inverter column signal in the seventh embodiment,

13 is a view showing an example of a combined logic circuit group applied to the present invention;

14 is a view showing a combined logic circuit in Embodiment 8 of the present invention;

15 is a view showing a combined logic circuit in Embodiment 9 of the present invention;

16 (a) and (b) show a latch in a tenth embodiment of the present invention;

17 is a circuit diagram showing a latch in Embodiment 11 of the present invention;

18 is a circuit diagram of an inverter column in Embodiment 12 of the present invention;

19 is a circuit diagram of an inverter column in Embodiment 13 of the present invention;

20 is a circuit diagram of a NAND gate in Embodiment 14 of the present invention;

21 is a circuit diagram of a NOR gate in Embodiment 15 of the present invention;

Fig. 22 is a circuit diagram of a clock inverter in Embodiment 16 of the present invention;

23 is a circuit diagram of a combined logic circuit in Embodiment 17 of the present invention;

24 is a circuit diagram of a latch in Embodiment 8 of the present invention;

25 is a circuit diagram of an output buffer in Embodiment 19 of the present invention;

FIG. 26 is a circuit diagram of an input buffer according to Embodiment 20 of the present invention; FIG.

27 is a circuit diagram of an NMOS dynamic circuit in accordance with Embodiment 21 of the present invention;

28 conceptually shows a twenty second embodiment of the present invention;

29 is a circuit diagram of a CMOS inverter in Embodiment 23;

30 is an operation timing diagram of a CMOS inverter in the twenty-third embodiment;

31 is a view showing a series of inverters in Example 24;

32 is a view showing an inverter column in Example 25;

33 is a diagram showing a CMOS inverter in Example 26,

34 is a circuit diagram of a level holding circuit in the twenty-seventh embodiment;

35 is a circuit diagram of a conventional CMOS inverter;

36 shows the subthreshold characteristics of a MOS transistor.

(Explanation of the sign)

V _T ... threshold voltage, M _N ... N-channel MOS transistor,

IN ... input signal, M _P ... P-channel MOS transistor,

S ... sub-dress hold amplitude, C _ox ... gate insulator capacitance,

C _D ... floor space consumption, C ... inverter,

S _C , S _S ... switch, R _C , R _S ... resistance,

V _CC , V _SS ... power, V _SL ... source potential,

OUT ... output signal, LC ... level conversion circuit.

Specific embodiments of the invention are described in more detail hereinafter with reference to the drawings.

(Example 1)

First, Figs. 1A and 1B show an embodiment suitable for explaining the principles of the present invention. 1A is a circuit diagram of an inverter according to an embodiment of the present invention. In FIG. 1A, L denotes a CMOS inverter and is composed of a P-channel MOS transistor M _P and an N-channel MOS transistor M _N.

The present invention can be applied not only to inverters but also to logic gates such as NAND and NOR or logic gate groups as described later.

However, for simplicity, only the case of inverters is described. S _C and S _S represent switches, and R _C and R _S represent resistors. Viewed by resistors R _C and R _S and switches S _C and S _S inserted in parallel between the power supply terminals V _CL , V _SL and the power supply V _CC , V _SS of the inverter L, respectively. The features of the embodiment are erased. This results in a reduction in subthreshold currents as described below.

In the period in which high speed operation is required, the switches _Sc and S _S are turned on, and the power supplies V _CC and V _SS are directly applied to the inverter L (hereinafter referred to as the high speed operation mode).

A high-speed operation is performed when the P-channel MOS transistor (M _P) and the N-channel MOS transistor (M _N) threshold voltage (V _T) is set to a level of. At this time, the sub-threshold current flows to the inverter L as previously described. However, this current is not a problem since it is usually very small compared to the operating current, that is, the load charge / discharge current.

On the other hand, in a period where low power consumption is required, the switches _Sc 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 low power consumption mode). Due to the voltage drop due to the sub-threshold current flowing through the resistor, V _CL drops below V _CC and V _SL rises above V _SS . As shown in Fig. 2, the subthreshold current is reduced by the voltage drop by the following two types of mechanism means. The N-channel MOS transistor M _N is described later when the input signal IN is at the low level V _SS , and the P-channel MOS transistor M _P when the input signal IN is at the high level V _CC . Also applies to

(i) As 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 _TO to V _T1 . . This rising part of the threshold voltage is expressed by the following equation.

In addition, the subthreshold current is reduced from I _LO to I _L1 .

The reduction ratio is then:

ego,

Where K is the substrate effect coefficient.

For example, when V _M = 0.3 V, K = 0.4√V, S = 100 mA / decade, and 2φ = 0.64 V, the sub-threshold current decreases to 21%.

(ii) As the source potential V _SL rises, the gate-source voltage V _GS = V _SS -V _SL = -V _M becomes negative. In addition, the sub-threshold current decreases from I _L1 to I _L2 , and this reduction is:

For example, V _M = 0.3VS = 100mV / decade, and the subthreshold current is reduced to 0.1%.

Considering the effects of (i) and (ii) together, the following equations are obtained.

For example, when V _M = 0.3 V, the subthreshold current is reduced to 0.02%.

Here, V _M is represented by the solution of the following equation.

In addition, the back gates of the MOS transistors M _P and M _N of the inverter L are connected to the respective sources V _CL and V _SL , but in order to obtain the effect of the contents of (i) of FIG. 1 (a) It is more preferable to connect the backgate to the power supply (V _CC , V _SS ) as shown in FIG.

3 shows the effect of reducing the subthreshold current. Here, assuming that future large-scale LSIs operate at extreme low voltages, when the backgate bias is zero, the threshold voltage V _TO = 0.05V at 0.15V, and the sum of the channel widths of the transistors in the off state for the entire LSI ( W) is calculated for W = 100m. As resistance increases, V _M becomes larger and the effect increases. In extreme cases, the resistance may be infinitely removed.

However, as shown in FIG. 1B, the logic voltage swing of the output signal OUT is smaller than the logic voltage amplitude of the input signal IN. Therefore, in the case of a multistage connection, attention should be paid to the voltage level of the signal, which is described later.

In addition, the present invention has a function to automatically compensate for the instability of the threshold voltage. In other words, when the threshold voltage is low and the sub-threshold current is high, the voltage drop V _M by the resistance is larger, and when the threshold voltage is high and the sub-threshold current is small, the voltage drop V _M is smaller. Lose.

In both cases, the instability of the current is suppressed. As shown in FIG. 3, the instability of the sub-threshold current decreases as the resistance value increases. For example, if the resistance value is set to 3K or more, the instability of the sub-threshold current I _L is suppressed to within ± 20% even if the threshold voltage fluctuates by ± 0.05V.

(Example 2)

Next, a specific method for realizing the resistor and the switch described in Embodiment 1 will be described.

4 shows an example of both a switch and a resistor realized by a MOS transistor. The switching MOS transistors M _C1 and M _{S1 each} have a large conductance and correspond to the switches S _C and S _S , respectively, as shown in FIG. In the high speed operation mode, the MOS transistors M _C1 and M _S1 are turned on by respectively setting the signal .phi.C to the low level and the signal .phi.S to the high level.

The voltage levels ΦC and ΦS become V _SS and V _CC , respectively, but the voltage level ΦC is set lower than the power supply V _SS to increase the conductance of the MOS transistors M _C1 and M _S1 . ΦS may be set larger than the power supply V _CC . The voltage may be generated by an on-chip booster circuit known in EEPROMs and DRAMs, or may be applied from the outside of the chip.

In the low power consumption mode, the MOS transistors M _C1 and M _S1 are turned off by turning the voltage level Φ C high and the voltage level Φ S low. At this time, the current must be completely suppressed. Two methods are used to achieve this goal. In the first method, the voltage level Φ C is made higher than the power supply V _CC and the voltage level Φ S is made lower than the power supply V _SS by means of an external voltage or an on-chip burst circuit. In the second method, M _C1 and M _S1 are used as transistors having a higher threshold voltage (higher) than the transistors used in the inverter L. The first method has the advantage that no process is required to produce transistors having different threshold voltages. On the other hand, the second method may be advantageous in that the area is reduced since no terminal for receiving an external voltage or an on-chip burst circuit is required.

The MOS transistors M _C2 and M _S2 have a small conductance and correspond to the resistors R _C and R _S , respectively, as shown in FIG. 1. These transistors are respectively connected to the power supplies V _SS and V _SS at their gates and always remain on. Since these transistors do not need to be turned off, there is no problem even if their threshold voltages decrease.

It is also possible to use an N-channel MOS transistor as the MOS transistor M _C2 and a P-channel MOS transistor as the MOS transistor M _S2 . For example, taking an N-channel MOS transistor of M _C2 as an example, a terminal connected to a gate and a drain is connected to a terminal V _CC , and a source is connected to a terminal V _CL . This can effectively realize the resistance. By controlling the channel width and the threshold voltage of the N-channel MOS transistor, the voltage V _CL can be set to the voltage dropped from the power supply V _CC by, for example, the threshold voltage of the N-channel MOS transistor during standby. have. Thus, the subthreshold current can be greatly reduced.

Next, the cycle applied to this invention is demonstrated. 5A to 5C illustrate examples of timings of the signals ΦC and ΦS.

5 (a) and 5 (b) show a case where the present invention is applied to a memory LSI. The memory LSI is a chip enable signal (a clock signal from an external device). When the (Complementary signal) is at low level, it enters the operating state and the signal ( Goes into standby when) is high level. In the case of FIG. 5A, the internal signal ΦC is a signal ( In synchronization with the falling of the A little behind the rise of) to enter the high level. The internal signal ΦS is shown in reverse with the above.

Thus, the period shown in (a) of the figure becomes the high speed operation mode and the period in (b) becomes the low power consumption mode. In general, in a memory device using a plurality of memory LSIs, the number of LSIs in operation is small and the majority of LSIs are in a standby state. Therefore, those LSIs in the standby state greatly contribute to obtaining the low power consumption of the entire memory unit when entering the low power consumption state used in the present invention. Also, until the signal enters the low power consumption mode, The reason for the delay at rise is that the LSI temporarily resets the internal circuit.

Fig. 5B also shows an embodiment aimed at low power consumption. Where signal ( Immediately after) is changed, only a part goes into high-speed operation mode. That is, data read / write is a signal ( ) Is executed immediately after entering the low level and the internal circuit ) Is reset immediately after entering the high level. Therefore, these periods enter the high speed operation mode according to the present invention and the other periods enter the low power consumption mode according to the present invention. Also, although not described here, it is arranged to enter the high speed operation mode when the address signal changes.

5 (c) shows an embodiment of the present invention applied to a microprocessor. The clock signal CLK is applied in a normal operating state. At this time, the signal .phi.C is at the low level and the signal .phi.S is at the high level, indicating that it is in the high speed operation mode. When the microprocessor enters the standby state or in the data hold state, the clock signal CLK is stopped and the signal BU goes high. The signal Φ C indicates a high level, and the signal Φ S indicates a low level in synchronism with the above, indicating that it is in a low power consumption mode. In addition, the power consumption of the microprocessor is reduced, so it is possible to back up the microprocessor for a long time with a small power supply such as a battery.

FIG. 6 shows an embodiment of the structure of an apparatus for realizing the circuit shown in FIG. Polysilicon 130, 131, 132, 133 in the figure corresponds to the MOS transistors M _C2 , M _P , M _N , M _S2 shown in FIG. 4 (M _C1 and M _S1 are not shown here).

It is to be noted that the MOS transistors M _C2 and M _P commonly maintain the same n-well 101 that is connected to the power supply V _CC through the n + diffusion layer 120. In addition, M _N and M _S2 maintain P-substrates commonly connected to V _SS in a similar manner to the above.

As can be seen from the foregoing, not only the effect described in (i) can be obtained, but also the back gate of the MOS transistor is connected to the power supply (V _CC , V _SS ) as compared with the back gate of the MOS transistor connected to the source. This is further advantageous in that the layout area is saved.

N-wells are formed in the P-substrate in the example shown here, but P-wells may also be formed in the n-substrate. Alternatively, this triple well structure can be applied as described in ISCC, Digest of Technical Paper, pages 248-249, published in February 1989.

(Example 3)

Another method for realizing switches and resistors is shown in FIG.

The characteristic of this embodiment is to use a current mirror circuit. That is, MOS transistors M _C2 and M _C3 having the same threshold voltage form what is called a current mirror circuit, and a current proportional to the current source I ₀ flows to the MOS transistor M _C2 having a large impedance. The same applies to the MOS transistors M _S2 and M _S3 . Thus, the MOS transistors M _C2 and M _S2 can be regarded as having a high resistance. The circuit CS composed of the current source I ₀ and the MOS transistors M _C3 and M _S3 may be held in common by a plurality of logic gates. The current mirror circuit is not limited to the circuit described here. Other circuits can also be used. For example, bipolar transistors can be used in place of MOS transistors. As described, many variations are possible as a way to realize switches and resistors. In short, any means may be used for applying a large current in a period in which high speed operation is required and a means for applying a small current in a period in which low power consumption is required. In the following, switches and resistors are shown in the figures for simplicity as shown in FIG. 1.

(Example 4)

The backgate of the MOS transistor of the inverter can be connected to another power supply not limited to the power supply V _CC , V _SS , and the voltage can also be made variable. An embodiment is shown in FIG.

The back gates of the MOS transistors M _P and M _N are here connected to the power supplies V _WW and V _BB , respectively, and their back gate voltage values change depending on standby and operation. With respect to the power supply V _BB , in a period where high speed operation is required, the power supply V _BB is made shallow (or slightly positive in extreme cases), and the threshold voltage V _T of the MOS transistor M _N is high speed. The operation is lowered to make it possible. In the period where low power consumption is required, the power supply V _SS is made deep and the threshold voltage V _T of the MOS transistor M _N is increased to suppress the sub-threshold current. In addition, the effect previously described in the content (i) is further increased. Although the power supply V _SS has already been described, the same applies to the power supply V _WW except when the voltage polarity is reversed. This type of backgate voltage generation circuit is also described on February 25, 1985, published by ISCC Digest of Technical Paper, pages 254-255.

FIG. 9 shows an embodiment of an apparatus structure for realizing the circuit shown in FIG. The triple well structure previously described herein is used and the n-well 105 (the back gate of the P-channel MOS transistor) is connected to the power supply (V _WW ) through the n + diffusion layer 120 and the p-well 103 (N channel). The back gate of the MOS transistor) is connected to the power supply V _SS through the p + diffusion layer 127.

This triple well structure has the advantage that the back gate voltage can be set for each circuit by combining both the P and N channels into wells that are dependent on each circuit. For example, it is possible to create a shallow backgate of the former and a deep backgate of the latter when the circuit is included in one LSI in the operating state and in the standby state.

(Example 5)

Next, a case of inverter rows connected in multiple stages will be described.

For the sake of simplicity, the principle of the second stage will first be described. Fig. 10A shows a circuit diagram in the case where it is connected to the CMOS inverters L ₁ and L ₂ . The switches S _C1 , S _S1 and the resistors R _C1 , R _S1 are inserted into the inverter at every step.

In the high speed mode of operation, all four switches are turned on and the power supplies V _CC , V _SS are applied directly to the inverters L ₁ , L ₂ . High speed operation is enabled by setting the threshold voltage of the MOS transistor of the inverter to low level. On the other hand, in the low power consumption mode, four switch modes are turned off and power is supplied to the inverter through the resistor. V _CL1 and V _CL2 fall below the power supply (V _CC ), and V _SL1 and V _SL2 become higher than the power supply (V _SS ) due to the voltage drop as the sub-threshold current flows through the resistor.

As for the inverter L ₁ of the first stage, the sub-threshold current is reduced by the mechanisms in (i) and (ii) described above in a similar manner to that in FIG. However, the logic voltage amplitude of the output N ₁ of the inverter L ₁ is less than the logic voltage amplitude of the input signal IN. That is, when the input signal IN is at low level (= V _SS ), the voltage level of N ₁ represents V _CL1 , and when the input signal IN is at high level (= V _CC ), the voltage level of N ₁ is V _SL1 . Indicates. Since the output N ₁ is the input of the inverter L ₂ in the second stage, the resistance value such that V _CC V _CL1 V _CL2 and V _SS <V _SL1 <V _SL2 are effective for reducing the subthreshold current of the inverter L ₂ . It is preferable to set. In addition, the sub-threshold current is also reduced by the mechanism in the above descriptions (i) and (ii) of the inverter L ₂ . When V _CL1 = V _CL2 and V _SL1 = V _SL2 , the effect by the content (i) is obtained, but the effect by the content (ii) is not obtained.

(Example 6)

The same applies to the multiple bonds shown in FIG. 11A, and the effects of V _CC V _CL1 V _CL2 ....> V _CLK and V _SS <V _SL1 <V _SL2 <..... <V _SLK It is recommended that it be obtained.

However, the logic voltage amplitude gradually decreases as shown in Fig. 11B, and the voltage amplitude is recovered by inserting an appropriate level conversion circuit. In this embodiment, the level converting circuit LC is added after the inverter at the Kth stage such that the logic voltage amplitude of the output signal OUT is equal to that of the input signal IN. This type of level conversion circuit is disclosed, for example, in June 1992, Digest of Technical Paper, VLSI, pages 82-83.

The level conversion circuit LC is not required in the high speed operation. The reason is that both switches are on, so V _CL1 = V _CL2 = .... = V _CLK = V _CC and V _SL1 = V _SL2 = .... = V _SLK = V _SS and the logic voltage amplitude This is because the decrease is small. Therefore, the delay can be avoided by turning on the switch S _LC so that the level converting circuit can be bypassed in the high speed operation.

(Example 7)

Fig. 12A shows another embodiment of the inverter column of the multistage connection. In this embodiment, all the switches S _C , S _S and the resistors R _C , R _S are commonly maintained by means of inverters L ₁ -L _K and the voltages V _CL , V _SL are inverters. It is common to (L ₁ -L _K ). Therefore, the threshold current reduction effect is obtained by the mechanism in the above-described content (i), but the effect by the content (ii) is not obtained as described with reference to FIG.

Thus, the subthreshold current reduction effect is less than that of the previous embodiment.

However, there is an advantage that the layout area of switches and resistors is saved. In addition, there is a characteristic that the voltage levels of all the signals including the input / output signal are the same, and there is no decrease in the logic voltage amplitude in the previous embodiment as shown in Fig. 12B. As a result, a logic circuit such as a NAND circuit and a NOR circuit can be easily manufactured without requiring a level change circuit.

(Example 8)

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

For example, consider the combinational logic shown in FIG. Logic gates were first grouped as shown in FIG. 13 for application to the present invention. In this embodiment, _fifteen of the logic gates L ₁ -L ₁₅ are divided into three groups G ₁ , G ₂ , and G ₃ . In the grouping, the output signal of the logic gate included in the i-th group is arranged to be input only to the logic gate of the (i + 1) -th group.

Next, as shown in FIG. 14, a switch and a resistor are inserted between each logic gate group and a power supply. The logic voltage amplitude of the output signal of the logic gate is sequentially decreased, similar to the case shown in FIG. 11B, and the level shift groups GC ₁ and GC ₂ are inserted as shown in FIG. 14 to recover the voltage amplitude. do. In addition, although not described, the level conversion groups GC ₁ and GC ₂ are bypassed in the high speed operation similarly to the case of Fig. 11A.

One of the features of the present embodiment is that logic gates included in the same group are commonly connected to a switch and a resistor. Referring to the embodiment shown in FIG. 13, three inverters are commonly included in a group G ₁ with resistors R _C1 , R _S1 and switches S _C1 , S _S1 .

Another feature of this embodiment is that switches and resistors are commonly connected by groups before and after the level conversion circuit. That is, the groups G ₁ and G _{K + 1} are commonly connected to the switches S _C1 and S _S1 and the resistors R _C1 and R _S1 , and the groups G ₂ and G _{K + 2 are} connected to the switch ( S _C2 , S _S2 ) and resistors (R _C2 , R _S2 ) are commonly connected, and groups (G _K , G _2K ) are common to switches (S _CK , S _SK ) and resistors (R _CK , R _SK ) Is connected.

As described above, the switch and the resistor are commonly connected by a plurality of logic gates, so that it is possible to reduce the number and resistance of the switches in all LSIs so as to save the layout area.

(Example 9)

Figure 15 shows another embodiment of the present invention. 15 is different from the embodiment described so far in the embodiment shown in FIG. 15 by the voltage limiter (voltage drop and voltage boosting circuit) (VC ₁ , VC ₂ ,..., VC _K ) and (VS ₁ , VS ₂ , ...,, VS _K ) is used.

When low power consumption is required, the switches T _C1 -T _CK and the switches T _S1 -T _SK are switched to the described side, so that power is supplied to the logic gate group by the voltage limiter means.

Voltage limiter _{(VC 1, VC 2, ...} , VC K) is a power supply voltage (V _CC) operating as a voltage step-down circuit, and the one power supply (V _CC) low almost stabilized internal voltage (V _CL1 than a, V _CL2 , ...., V _CLK ) respectively.

On the other hand, VS ₁ , VS ₂ , ...., VS _K operate as a boosting circuit on the ground (V _SS ) side, and almost stabilized internal voltage (V _SL1 , V _SL2 , ...) higher than voltage (V _SS ) , V _SLK ) respectively.

It is recommended that V _CC V _CL1 V _CL2 ....> V _CLK and V _SS <V _SL1 <V _SL2 <... <V _SLK for the generated voltage similar to the previously described embodiment. This type of voltage limiter is also disclosed in JP-A-2-246516.

In contrast to the above description, when the switch is switched to the opposite side when the high speed operation is required, the power supplies V _CC and V _SS are directly applied to the logic gate group to enable the high speed operation. In addition, since the voltage limiter is no longer needed at this time, the operation is stopped.

(Examples 10 and 11)

Circuits without feedback, such as inverter columns and combinational logic circuits, have been used in the previous embodiments, but the present invention also applies to circuits with feedback. The case of a latch circuit obtained by combining two nand gates shown in Fig. 16A will be described as an embodiment.

(B) of FIG. 16 shows a circuit diagram. The switches (S _C1 , S _S1 , S _C2 , S _S2 ) and resistors (R _C1 , R _S1 , R _C2 , R _S2 ) have two nandgates (L ₁ , L ₂ ) and power (V _CC ) and ground ( V _SS ) is inserted between each. V _CL1 and V _CL2 decreases lower than V _CC , and V _SL 1 and V _SL2 increase higher than V _SS so that the subthreshold voltage is reduced by the mechanism in the foregoing description (i).

FIG. 17 shows four MOS transistors M _P12 for latching information, made larger (more enhanced) than other MOS transistors M _P11 , M _P2 1, M _N11 , M _N21 to further reduce the subthreshold current. , M _P22 , M _N12 , M _N22 ) represents an embodiment in which the threshold voltage V _T is used.

Since the threshold voltage V _T of the other MOS transistors M _P11 , M _P21 , M _N11 , M _{N21 to} which the input signal is applied remains at the low level, high-speed operation is possible. In this case, the resistance of the switch and the power supply V _SS side is not necessary. This is because the current can be reliably suppressed by the means of the transistors M _N12 and M _N22 on the power supply VSS side having a high threshold voltage.

(Examples 12 and 13)

In the embodiments shown so far, it is possible to reduce the sub-threshold current in both the input signal at which the low level or high level is turned on. However, it is already known that the level of a specific signal, i.e., in the standby state, is large in a period in which the sub-threshold current reduction is required in practical LSI. In such a case, it is possible to reduce the subthreshold current by a simpler circuit.

Fig. 18 shows an embodiment of the circuit of the inverter column in the case of recognizing that the input signal IN is at the low level "L" in the standby state.

Since the input signal IN is at the low level, the nodes N ₁ , N ₃ , N ₅ , ... represent a high level and the nodes N ₂ , N ₄ , N ₆ , ... Indicates. Thus, M _P2 , M _P4 , ... between the P-channel MOS transistors are off and M _N1 , M _N3 , ... between the N-channel MOS transistors are off. It is sufficient to insert switches and resistors at the source of those transistors in the off state, which is the transistor in the off state through which the sub-threshold current flows.

In addition, as shown in FIG. 19, if the switch and the resistor are commonly connected by means of a plurality of inverters, there is no problem. Although these embodiments have a limitation that the level of the input signal must be known in advance, the sub-threshold current can be reduced by a simple circuit. As can be seen more clearly when comparing FIG. 18 and FIG. 19 with FIG. 11A, a large number of switches and resistances are saved and a level conversion circuit is not necessary.

(Example 14, 15)

Not only in the inverter, but also in the logic gates such as the NAND and NOR gates, it is possible to reduce the subthreshold current by a simpler circuit when the level of the input signal is known in standby. 20 shows an embodiment of two input nAND gates, and FIG. 21 shows an embodiment of two input nOR gates. When both of the two input signals IN ₁ and IN ₂ are low level or all high level, these gates are actually equivalent to the inverter.

Therefore, the method described in FIGS. 18 and 19 is applied. As shown in the figure, a problem exists when one input is low level "L" and the other input is high level "H".

In the case of the NAND gate shown in FIG. 20, the P-channel MOS transistor M _P12 and the N-channel MOS transistor M _N11 are off. However, it is the MOS transistor M _N11 that the output OUT is at high level and the subthreshold current flows through. So it is enough to insert a switch and resistor on the V _SS side. Conversely, in the case of the NOR gate shown in FIG. 21, it is the P-channel MOS transistor M _P14 that the sub-threshold current flows into. Therefore, it is sufficient to insert a switch resistor on the power supply (V _CC ) side.

20 and 21 show an embodiment in which the present invention is applied to two input logic gates, but the present invention can be applied to a similar method with logic gates having three or more inputs.

In addition, it is natural that a switch and a resistor are commonly connected to another logic gate.

(Example 16)

FIG. 22 is an example of a circuit in the case where the clock CLK ₁ is low level and the clock CLK ₂ is high level in the standby clock inverter. In this case, since the MOS transistors MP16 and M _N16 are off, the output OUT has a high impedance, and its voltage level is determined by another circuit (not shown) connected to the output OUT. Since it is determined by the voltage levels of the transistors M _P16 and M _N16 through which the sub-threshold current flows, in this case, it is sufficient to insert a switch and a resistor on both sides of the V _CC and V _SS sides.

(Example 17)

In the general combinational logic circuit, it is possible to reduce the subthreshold current by a simpler circuit when the level of the input signal is known in advance.

As an example, the combinational logic shown in FIG. 23 will be described.

Fig. 23 shows an example of the circuit structure in the case where it is recognized that all of the inputs 1N ₁ -1N ₆ of this circuit are low level.

With respect to the inverters L _1- L ₃ , L ₅ , L ₆ , the switches and resistors are placed on the V _SS side of the inverters L _1- L ₃ and the inverters L ₅ , L ₆ , similar to FIGS. 18 and 19. Will be inserted into

Since all of the input signals are low level, the NOR gate L ₇ is actually equivalent to the inverter. Thus, it is possible to insert a switch and a resistor on the V _SS side.

Since one of the input signals is low level and the other is high level for the NOR gate L ₄ , a switch and a resistor are inserted into the V _CC side similarly to FIG. 21. Since all three input signals to L ₁₂ of the eight NAND gates are low level and L ₁₂ is equivalent to the inverter, a switch and resistor are inserted on the V _CC side. Since the input signals on the low level and high level are included in other NAND gates, a switch and a resistor may be inserted into the V _SS side similarly to FIG. 20.

As will be apparent from the above description, it is sufficient to insert switches and resistors on the V _SS side for logic gates with high level output and on the V _CC side for logic gates with low level output. The area of the layout can be saved by commonly accommodating the switch and the resistor with a plurality of logic gates.

(Example 18)

If the signal level is known in advance, it is possible to reduce the subthreshold current by a simple circuit with feedback. FIG. 24 shows an example in which the present invention is applied to the latch circuit shown in FIG.

In the latch circuit of the above kind, the input signals IN ₁ and IN ₂ are both at a high level in the standby state, one of the output signals OUT ₁ and OUT ₂ is at a low level, and the other is at a high level. Has information. FIG. 24 shows an example of a circuit structure when the output signal OUT ₁ is at a low level and the output signal OUT ₂ is at a high level. The NAND gate L ₁ is equivalent to the inverter because both input signals are high level, and a switch and a resistor are inserted at the V _CC side similarly to FIGS. 18 and 19. Since one of the input signals of the NAND gate L ₂ is low level and the other is high level, a switch and a resistor may be inserted into the V _SS side similarly to FIG. 20. Naturally, the switch and the resistor are commonly connected together with other logic circuits.

(Example 19)

25 shows an example in which the present invention is applied to a known data output buffer such as a memory (LSI) or the like. In the standby state, the output enable signal OE is at the low level, the outputs of the NAND gates L ₂₁ and L ₂₂ are at the high level, and the output of the inverter L ₂₃ is at the low level. Therefore, the two MOS transistors M _P20 and M _N20 constituting the output terminal L ₂₄ are both in an off state, and the output DOUT has a high impedance.

For the logic gates L ₂₁ to L ₂₃ , a switch and a resistor may be inserted into the V _SS or V _CC side according to a predetermined means in the description with reference to FIG. 23. For the output terminal L ₂₄ , a switch and a resistor may be inserted at both the V _CC and V _SS sides in a manner similar to the clock inverter shown in FIG. 22.

(Example 20)

Fig. 26 shows an example in which the present invention is applied to a data input buffer known in a memory (LSI) or the like. In FIG. 26, SB displays a signal indicating a high level in the standby state.

The outputs of the inverters L ₃₁ , L ₃₂ are used as signals Φ S and Φ A for controlling the switches shown in FIGS. 4 and 7, respectively. L ₃₃ represents a nand gate and receives ΦS and a data input signal (D _IN ). Since Φ S is low level in the standby state, the output of L ₃₃ represents a high level regardless of the input signal D _IN . Therefore, the output d _IN of the inverter L ₃₄ represents a low level. On the other hand, since SB is low level in the operating state, the output d _IN is generated as a result of the input signal D _IN .

For the NAND gate L ₃₃ and the inverter L ₃₄ , the sub-threshold current can be reduced by inserting switches and resistors on the V _SS and V _CC sides, respectively. Although the above techniques are not used in inverters L ₃₁ and L ₃₂ , the sub-threshold current can be reduced by increasing the threshold voltage of the MOS transistor. In many cases of transition from the operating state to the standby state, there is no problem in using a MOS transistor with a high threshold voltage since high speed operation is not necessary very much.

The data input buffer described above is used as an input buffer for address signals and other signals. 18 to 25 have the advantage that the sub-threshold current can be reduced by a simple circuit, while on the other hand, the above-described embodiments provide a signal level when the sub-threshold current is required to be reduced, i.e., in a standby state. There is a limitation that cannot be applied unless it is recognized. Therefore, it is desirable to set as many levels of nodes as possible at this time in the LSI. By using a circuit such as the input buffer shown in Fig. 26 as the above means, it is possible to set the level of the signal d _IN to the low level at this time. As a method for determining the level, there is also a method having a specification that "the data input terminal D _IN becomes low level (or high level) in the standby state" by a method other than the above method. 18 to 26 are suitable for use with memory (LSI).

This is because, since there are many nodes whose high level or low level is known at the time of the standby state in the memory LSI, the level of most nodes can be set using the input buffer shown in FIG.

25 and 26 may be used not only as an input / output circuit for an external terminal of an LSI chip but also as a driver / receiver for an internal bus of a microprocessor, for example.

This embodiment may correspond to the claims herein. However, the invention described in the claims has the input buffer shown in Fig. 26 as an input control circuit and a switch element. That is, according to the present invention, the input signal is input from the input buffer shown in FIG. 26 to the input terminal of the common gate of the first and second MOS transistors. The switch element is turned on and off in accordance with a control signal to realize the first and second states. In particular, in the first claim, when the first MOS transistor is a P-channel MOS transistor, the second MOS transistor becomes an N-channel MOS transistor. Conversely, when the first MOS transistor is an N-channel MOS transistor, the second MOS transistor becomes a P-channel MOS transistor. In any case, it is possible to obtain the effect of the present invention. (Example 21)

Although the embodiments to which the present invention is applied to a CMOS circuit have been described so far, the present invention can also be applied to a circuit composed of a MOS transistor having unipolarity. Fig. 27 shows a circuit example composed of only N-channel MOS transistors. In FIG. 27, the PC displays a precharge signal and the IN ₁ and IN ₂ display an input signal.

At standby, i.e. in the precharge state, the PC is at high level, the inputs IN ₁ and IN ₂ are at low level and the output OUT is precharged to high level (= V _CC -V _T ). In operation, the inputs (IN ₁ , IN ₂ ) go high or remain low after the PC goes low. When at least one of the inputs IN ₁ , IN ₂ goes high, the output OUT goes low. If all of the inputs IN ₁ and IN ₂ remain low, the output OUT remains high. In other words, the circuit outputs the NOR of the inputs IN ₁ and IN ₂ .

In the circuit, the V _SS side M _N41 and M _N42 are transistors that are off in the waiting time, and a sub-threshold current flows in the transistor. Therefore, in order to apply the present invention to the circuit, a switch and a resistor may be inserted into the V _SS side shown in the drawing. These are not needed on the V _CC side.

As described above, the present invention is very effective for achieving low power consumption of MOS transistor circuits and semiconductor integrated circuits composed thereof. In particular, in recent years, the demand for low power consumption of semiconductor integrated circuits has increased, and for example, a microprocessor system with a low power backup mode is described on Nikkei Electronic, pages 106-111, September 2, 1991. In the backup mode, the clock stops and the parts that do not need power supply are stopped in turn, thereby inducing low power consumption. However, the range of subthreshold current reduction is not considered.

For example, low power consumption can be realized when the present invention is applied to a circuit that can be powered on and resumed even in backup mode.

(Example 22)

In the above-described embodiment, there is a problem that the logic voltage amplitude decreases with an increase in the number of stages, and when the voltage level of the input signal is unknown, a rather complicated design is required. Fig. 28 shows a circuit for solving the above problems, which is switched on to perform normal high speed operation in a required time period until the logic output is set as described so far. At other times than the above, the sub-threshold current path of the logic circuit is interrupted by switching off.

However, when the switch is turned off, the supply path of the power supply voltage is cut off, so the output of the logic circuit becomes unstable, and the logic output is no longer stable. Therefore, one type of latch circuit (level holding circuit) for maintaining the voltage level is provided at the output. If a transistor having a high threshold voltage or the like is used for the level holding circuit, the sub-threshold current of the level holding circuit is negligibly small, so that it is possible to reduce the sub-threshold current as a whole. The delay time is hardly affected by the level holding 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, the current consumption is only a current flowing through the level holding circuit since there is no current flowing through the logic circuit in the standby state. Since the level keeping circuit only maintains the output, the driving capability is small, and thus it is possible to reduce the current consumption. Since the output of the logic circuit is held by the level holding circuit even when the switch is turned off, there is no possibility of output inversion and the operation is stabilized. Therefore, a semiconductor device that can stably operate at low power consumption and at high speed can be realized. According to this embodiment, since the voltage level is always guaranteed by the means of the level holding circuit, the logic voltage fluctuation is never reduced with the increase in the number of logic stages. Also, this embodiment is efficient regardless of the logic input.

This embodiment is further described with reference to FIG. The logic circuit LC is connected to the power supply line VHH at high potential and the power supply line VLL at low potential through the switches SWH and SWL. Here, it is possible to correspond VHH and VLL respectively to V _CC and V _SS described so far. The level holding circuit LH is connected to the output terminal OUT of the logic circuit LC. The switches SWH and SWL are adjusted by the control pulse CK so that the switches are turned on and off at the same time. The logic circuit LC is composed of a logic gate such as an inverter, a NAND circuit, a NOR circuit, a flip-flop circuit, or a plurality of combinations thereof. The level holding circuit LH may be configured as a positive feedback circuit.

The operation of the logic circuit is executed by turning on the switches SWH and SWL. After the output OUT is set according to the input IN of the logic circuit LC, the switches SWH and SWL are turned off, and the current path from VHH to V _LL is interrupted through the logic circuit LC, and the logic circuit LC ) Is held by the level holding circuit LH.

The delay time of the circuit is hardly influenced by the level holding circuit LH and is determined in the logic circuit LC. By using a circuit having a large driving capability with respect to the logic circuit LC, it is possible to execute a high speed operation with a short delay time. For example, since there is no current flowing through the logic circuit LC in the standby state, the current consumption is only the current flowing through the level maintaining circuit LH. Since the level holding circuit LH having a small driving capability is sufficient, the current consumption can be reduced. In addition, since the output OUT of the logic circuit LC is held by the means of the level holding circuit LH, there is no possibility of malfunction. Therefore, a circuit that executes stable operation at low power consumption and high speed can be realized.

(Example 23)

An embodiment in which the present invention is applied to a CMOS inverter is shown in FIG. The NMOS transistor MN1 and the PMOS transistor MP1 operate like the switches SWL and SWH shown in FIG. 28, respectively. When the switch is turned off, the threshold voltages of the transistors MN1 and MP1 are sufficiently high to generate a leakage current. The channel width and / or channel length is determined so that the on-state resistance does not increase. The control pulse CK is input to the gate of the NMOS transistor MN1 and the control pulse CKB is input to the gate of the PMOS transistor MP1. CKB indicates the complementary signal of CK. The CMOS inverter INV composed of the NMOS transistor MP2 and the PMOS transistor MP2 is connected to the transistors MN1 and MP1. In the low voltage operation, the threshold voltages of the transistors MN2 and MP2 are lowered to increase the driving capability. The level holding circuit LH composed of the NMOS transistors MN3 and MN4 and the PMOS transistors MP3 and MP4 is connected to the output terminal OUT of the inverter INV. While maintaining the output, the threshold voltages of the transistors MN3, MN4, MP3, and MP4 are high enough so that the channel width and / or channel length are sufficiently small. An example of the numerical values of the power supply voltage and the threshold voltage will be shown. VLL is set to ground potential at 0V and VHH is set to external supply voltage at 1V. The threshold voltage of the NMOS transistor is set to 0.2V for MN2 and 0.4V for MN1, MN3, and MN4. The threshold voltage of the PMOS transistor is set to -0.2V for MP2 and -0.4V for MP1, MP3, and MP4.

The operation will be described with reference to the timing diagram shown in FIG. First, the control pulse CK is raised to VHH, CKB is lowered to VLL, transistors MN1 and MP1 are turned on, and inverter INV is connected to VHH and VLL. When the input signal IN rises from VLL to VHH, MP2 is turned off, MN2 is turned on and the output OUT is discharged from VHH to VLL. The transistor MN2 starts to energize in the saturation region, and the current value flowing through the transistor 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 the VLL, the potential of the node NL temporarily rises due to the on-state resistance of the transistor MN1 and the current flowing from the transistor MN2. However, because the gate of the transistor MN1 is VHH, even if the threshold voltage is high, it is possible to design such that the on-state resistance is sufficiently small, and thus the effect on the delay time is reduced. In addition, when the output OUT is inverted to VLL, the transistor MN4 is in the off state and the transistor MP4 is in the on state so that the level maintaining circuit LH maintains the output OUT at VHH. As a result, the transistor MN2 is turned on and a through current flows from VHH to VLL through the transistors MP4 and MN2, but the effect on the delay time and the consumption current is higher than that of the transistor MN2. It becomes small by designing small. When the output OUT is lowered, the transistor MN3 is turned off, the transistor MP3 is turned on, in the level maintaining circuit, the node NLH is inverted from VLL to VHH, the transistor MN4 is turned on and the transistor ( MP4) is turned off, and the level holding circuit LH is operated to hold the output OUT at the VLL to wait for the stop of the through current. The transistor MP2 is off because both the gate and the source are VHH, but the through current flows through the inverter INV because the leakage current is large and the threshold voltage is low. At this time, the control pulse CK is lowered to VLL, CKB is raised to VHH, and the transistors MN1 and MP1 are turned off to separate the inverter INV from VHH and VLL. At this time, since the transistors MN1 and MP1 have the same potential as the gate and the source, the transistors are completely turned off and the threshold voltage is high. The output OUT is held at VHH by the level of the level holding circuit LH. The node NL remains at VLL because the NMOS transistor MN2 is on. On the other hand, the voltage of the node NH starts to fall from the node NH to the output terminal OUT due to the leakage current of the PMOS transistor MP2. At this time, the source potential is lower than the gate potential and the transistor MP2 is completely turned off. As a result, the through current of the inverter INV does not flow in the standby state. In addition, before the input signal IN changes, the control pulse CK is raised to VHH, CKB is lowered to VLL, and the transistors MN1 and MP1 are turned on so that the node NH becomes VHH. Since the input signal IN is inverted from VHH to VLL, the output OUT is inverted from VLL to VHH.

It is preferable that the level holding circuit LH quickly follows the output OUT so that the time interval is shortened when the through current flows through the inverter INV and the level holding circuit LH. Therefore, the inverter INV and the level holding circuit LH are closely arranged with each other to reduce the wiring delay.

As is apparent from this embodiment, the logic circuit without increasing the through current in the standby state when the threshold voltage of the MOS transistor used as the switch becomes about 0.4V or more required to reduce the subthreshold current. It is possible to reduce the threshold voltage of the MOS transistor at. Even if the operating voltage is lowered to 1V or lower, it is possible to set the threshold voltage of the MOS transistor to 0.25V or lower, thereby making the driving capability stable. Therefore, low power consumption can be realized by lowering the voltage.

In addition, performance improvement can be realized by proportionally reducing the element based on the conventional law of proportional reduction. Also, since the structure is the same structure as the conventional CMOS logic circuit except that the position and level holding circuits are loaded, the same conventional design technique can be used.

(Example 24)

Fig. 31 shows an embodiment in which the present invention is applied to a CMOS inverter train. The inverter train can be realized by a multilayer connection of a structure in which two switches and one level maintenance circuit are installed on the inverter in one stage shown in Fig. 29, but the present embodiment is designed to reduce the number of elements and the area in order to reduce the number of elements. This is an example in which a switch and a level holding circuit are commonly accommodated by an inverter.

Here, the inverter rows are illustrated in four stages, but in a similar manner in the case of including different numbers of stages. Four inverters INV1, INV2, INV3, and INV4 are arranged in series. The level holding circuit LH is connected to the output terminal of the inverter INV4 at the final stage. Each inverter is composed of one PMOS transistor and one NMOS transistor, similar to the inverter INV shown in FIG. In each inverter, the size of the transistors is the same or different from each other. It is possible to increase the INV1, INV2, INV3 and INV4 channel widths in order between stages while having the same channel length as is often used as a serial driver. The source of the PMOS transistor of each inverter is connected to the node NL, and the source of the NMOS transistor is connected to the node NL. The switch SWL is installed between the node NL and the power supply VLL to be at the low level, and the switch SWH is installed between the node NH and the power supply VHH to be at a high level. The switches SWL and SWH are adjusted by the control pulse CK and are turned on and off at the same time. As shown in Fig. 29, the switch SWL is realized by the NMOS transistor, and the switch SWH is realized by the PMOS transistor using the complementary signal of CK at the gate.

The operation of the inverter string is executed by turning on the switches SWL and SWH. For example, when the input signal IN is inverted from the low level VLL to the high level VHH, the node N1 is inverted from VHH to VLL by the inverter INV1, and the node N2 is the inverter. Invert VIN to VHH by INV2, node N3 is inverted from VHH to VLL by inverter INV3, and output OUT is inverted from VLL to VHH by inverter INV4. When the output OUT is set to VHH, the level holding circuit LH operates to maintain the output OUT at VHH. In standby, the current path from VHH to VLL through the inverter is broken by turning off the switches SWL, WH.

In this embodiment, it is sufficient to provide a level holding circuit at the output terminal by adjusting the inverter string as a whole as one logic circuit. In addition, the switches SWL and SWH may be commonly accommodated by a plurality of inverters. The size of the switches SWL and SWH is determined by the magnitude of the applied peak current. The sum of the peak currents flowing in the plurality of inverters becomes smaller than the sum of the peak currents in each inverter. For example, when the inverter string is formed at the inner stage ratio 3, the sum of the peak currents is almost equal to the peak current at the final stage. Therefore, the area of the switch may be sufficient when the switch is commonly accommodated by a plurality of inverters as compared to the case where the switch is installed in all inverters.

(Example 25)

32 shows another example in which the present invention is applied to an inverter column. The case of inverter rows in four stages is similarly illustrated in FIG. 31, but the inverter array is similarly configured even when the number of stages is different. Four inverters INV1, INV2, INV3, and INV4 are connected in series. The level holding circuits LH3 and LH4 are connected to the node N3, which is an output terminal of the inverter INV3, and an output terminal OUT of the inverter INV4, respectively, which are input terminals of the inverter INV4. Each inverter is composed of one PMOS transistor and one NMOS transistor similarly to the inverter shown in FIG. Radix inverters INV1 and INV3 are connected to nodes NL1 and NH1, and even inverters INV2 and INV4 are connected to nodes NL2 and NH2. The switches SWL1 and SWL2 are provided at the low level between the nodes NL1 and NL2 and the power supply VLL, respectively, and the switches SWH1 and SWH2 are respectively at the high level between the nodes NH1 and NH2 and the power supply VHH. Is provided. The switches SWL1 and SWL2 and the switches SWH1 and SWH2 are controlled by the control pulse CK to be turned on and off at the same time.

The operation of the inverter is executed by turning on the switches SWL1, SWL2, SWH1, SWH2. For example, when the input signal IN is inverted from the low level VLL to the high level VHH, the node N2 is inverted from VLL to VHH, and the node N3 is inverted from VHH to VLL, and the output terminal is inverted. (OUT) is inverted from VLL to VHH by the inverter INV4 in successive order. When the node N3 is set to VLL, the level holding circuit LH3 operates to hold the node N3 at the VLL. In addition, when the output OUT is set to VHH, the level holding circuit LH operates to maintain the output OUT at VHH. For example, in the standby state, the current path from VHH to VLL through the inverter is interrupted by turning off the switches SWL1, SWL2, SWH1, SWH2. At this time, since the node N3 is held at the low level VLL by the level holding circuit LH3, the node NL1 is also held at the low level VLL through the inverter INV3. The node N1 is also maintained at the low level VLL through the inverter INV1. Similarly, nodes NH2 and N2 are also held at high level VHH by the output terminal OUT being held at high level VHH by level holding circuit LH4.

Therefore, the nodes connected between the inverters are maintained at the high level VHH or the low level VLL.

As described above, the nodes N1, N2, N3 between the inverters connect the odd and even inverters to different switches and connect the level maintenance circuit to some output terminal of the odd inverter and some output terminal of the even inverter respectively. By providing two sets of switches, the whole is kept at high level or low level. Even if the standby state is prolonged, the operation to the inverter is stable since the input to the inverter does not become an intermediate level.

In the embodiment shown in Figs. 29-32, the present invention has been applied to CMOS inverters and inverter columns. However, the present invention is not limited to the above described embodiments so far unless the stable operation by loading the switch and the level holding circuit into the logic circuit deviates from the gist of being executed at high speed with low power consumption.

(Example 26)

For example, another embodiment in which the present invention is applied to a CMOS inverter is shown in FIG.

In the embodiment shown in Fig. 29, the transistors MN1 and MP1 operating as switches are provided between the CMOS inverter INV and the power supplies VLL and VHH. In contrast to the above, these transistors are provided between the NMOS transistor and the PMOS transistor of this embodiment.

Two NMOS transistors MN2 and MN1 and two PMOS transistors MP1 and MP2 are connected in series between the low level power supply VLL and the high level power supply VHH. The NMOS transistor MN1 and the PMOS transistor MP1 operate as switches. When the transistor is turned off, the threshold voltages of the transistors MN1 and MP1 are increased to reduce the leakage current. The control pulse CK is inputted to the gate of the NMOS transistor MN1, and the control pulse CKB, which is the complementary signal of CK, is inputted to the gate of the PMOS transistor MP1. The NMOS transistor MN2 and the PMOS transistor MP2 are connected to the input terminal IN at a gate and operate like a CMOS inverter. In the low voltage operation, the threshold voltages of the transistors MN1 and MP1 are lowered to increase the driving capability.

The level holding circuit LH configured similarly to Fig. 29 is connected to the output terminal OUT. The operation is executed in a similar manner as in the embodiment shown in FIG. The transistors MN1 and MP1 are turned on by the control pulses CK and CKB so that the transistors MN2 and MP2 operate like a CMOS inverter. For example, when the input IN is inverted from the low level VLL to the high level VHH, the transistor MN2 in the off state starts conduction and operation in the saturation region. At this time, the current value of the transistor MN2 is determined by the gate-source voltage. Since the transistor MN1 is provided between the transistor MN2 and the output terminal OUT, the on-state resistance of the transistor MN1 is connected to the drain of the transistor MN2. As a result, the effect of the on-state resistance of the transistor MN1 on the current value of the transistor MN2 is small. After the output OUT is set, the transistors MN1 and MP1 are turned off to prevent the through current and maintain the output OUT by the level maintaining circuit LH.

As in the present embodiment, when the switch is inserted on the output terminal side of the logic circuit, it is impossible to accept the switch in common by the plurality of logic gates, but the influence of the on-state resistance of the switch is small. The same is true when the transistor is used as a switch, and the delay time is reduced as compared with the case where the switch is installed on the power supply side of the logic circuit as in the embodiment shown in FIG. Alternatively, if the delay times are designed to be the same, the channel width and / or channel length of the transistor used as the switch can be reduced to reduce the area.

(Example 27)

34 shows another structural example of the level holding circuit. A case will be described in which the level holding circuit is replaced with a level holding circuit composed of NMOS transistors MN3 and MN4 and PMOS transistors MP3 and MP4 in the embodiment shown in FIG.

This level maintenance circuit is composed of three NMOS transistors MN3, MN4 and MN5 and PMOS transistors MP3, MP4 and MP5, respectively. In the standby state, the threshold voltage of each transistor is increased to reduce leakage current. For example, it is set to 0.4V for an NMOS transistor and -0.4V for a PMOS transistor. Transistors MN3 and MP3 form an inverter, and transistors MN4, MN5, MP4 and MP5 form a clock inverter.

The control pulse CKB is input to the gate of the transistor MN5, and the control pulse CK is input to the gate of the transistor MP5. The operation timing is the same as when the level holding circuit LH shown in FIG. 29 is used as shown in FIG. In order to operate the inverter INV, the control pulse CK is raised to the high level VHH and the control pulse CKB is lowered to the low level VLL. At this time, the transistors MN5 and MP5 are turned off in the level maintaining circuit. As a result, when the output OUT is inverted, the through current does not flow through the inverter INV and the level maintaining circuit, and the delay time and current consumption are reduced. In the standby state, the control pulse CK is lowered to the low level VLL, the control pulse CKB is raised to the high level VHH, and the inverter INV is disconnected from the power supplies VLL and VHH. At this time, the transistors MN5 and MP5 are turned on in the level maintaining circuit and the output is held by positive feedback.

As described above, the transistors are increased by two for forming the level holding circuit by the combination of the inverter and the clock inverter, but the logic and level holding circuits no longer collide with each other and the delay time and current consumption are reduced. In addition, even when the driving capability of the level holding circuit is increased and the leakage current flowing through the output terminal is large, there is no possibility of output fluctuation at all, thereby enabling stable operation.

While each embodiment of the present invention described above uses an MOS semiconductor circuit device as an example, the present invention can also be applied to a metal insulated semiconductor (MIS) circuit device.

Claims (22)

A first operating potential point for supplying a first operating potential, A second operation potential point for supplying a second operation potential, A first node and a second node, A first MOS transistor of a first conductivity type having a source connected to the first node, a gate connected to the input node, and a drain connected to the output node; A second MOS transistor of a second conductivity type whose source is connected to a second node electrically connected to the second operating potential point, whose drain is connected to the output node, and whose gate is connected to the input node; , An input control circuit connected to the input node, A switch element provided between the first node and the first operation potential point to receive a control signal, When the control signal is in the first state, the switch element is turned on and according to the level of the input signal input to the input node, the first MOS between the first operation potential point and the output node. Allowing a first current to flow through the source / drain path of the transistor or through the source / drain path of the second MOS transistor between the second operating potential point and the output node, In response to the control signal being set to a second state different from the first state, the input control circuit controls the level of the input node to a predetermined level regardless of the level of the input signal, The switch element is turned off to limit the current flowing through the source / drain path of the first MOS transistor between the first operating potential point and the second operating potential point to a second current smaller than the first current. and, When the first operating potential point is a potential higher than the second operating potential point, the first MOS transistor is a P-channel MOS transistor, and the predetermined level is set to a high level, and the second operating potential point is the first operating potential point. And the first MOS transistor is an N-channel MOS transistor when the potential is higher than a dot, and the predetermined level is set at a low level. The method of claim 1, Even if the potential difference between the source and gate of the first MOS transistor is 0 V, a sub-threshold current flows in the source / drain path of the first MOS transistor, A sub-threshold current flows through a source / drain path of the second MOS transistor even if the potential difference between the source and gate of the second MOS transistor is 0V. The method according to claim 1 or 2, And a resistance element provided between the first node and the first operation potential point in parallel with the switch element, In response to the control signal being set to the first state, the switch element is turned on, and the first current mainly flows through the switch element, And in response to the control signal being set to the second state, the switch element is turned off and the second current flows primarily through the resistor element. The first potential point, The second operation potential point, A first node and a second node, The source is connected to the first node, has a source / drain path between the first node and the second node electrically connected to the second operating potential point, and the gate is connected to an input node. A logic circuit comprising a first MOS transistor, A switch element provided between the first node and the first operation potential point to receive a control signal; An input control circuit connected to the input node to receive an input signal, In the first MOS transistor, a leakage current flows in the source / drain path even when the potential difference between the source and gate is 0V. When the control signal is in the first state, the switch element is turned on to allow the first current to flow in the source / drain path of the first MOS transistor according to the level of the input signal input to the input node. , In response to the control signal being set to a second state different from the first state, the input control circuit controls the level of the input node to a predetermined level regardless of the level of the input signal, The switch element is turned off to limit the current flowing through the source / drain path of the first MOS transistor between the first operating potential point and the second operating potential point to a second current smaller than the first current. , When the first operating potential point is a potential higher than the second operating potential point, the first MOS transistor is a P-channel MOS transistor, and the predetermined level is set to a high level, and the second operating potential point is the first operating potential point. And the first MOS transistor is an N-channel MOS transistor when the potential is higher than a dot, and the predetermined level is set at a low level. The method of claim 4, wherein And a resistance element provided between the first operation potential point and the first node in parallel with the switch element, In response to the control signal being set to the first state, the switch element is turned on, and the first current mainly flows through the switch element, And in response to the control signal being set to the second state, the switch element is turned off and the second current flows primarily through the resistor element. A semiconductor integrated circuit device having at least two states, wherein the first state is lower power consumption than the second state. The first operation potential point, The second operation potential point, The first node, The second node, A first MOS transistor having a source / drain path between the first node and the second node, the source of which is connected to the first node and receives a first signal; A switch provided between the first node and the first operation potential point to receive a second signal; Having an input control circuit for outputting the first signal, The second node is electrically connected to the second operating potential point, In the first MOS transistor, even if the potential difference between the source and the gate is 0 V, a leakage current flows in the source and drain paths. When the semiconductor integrated circuit device is in the second state, the switch is turned on in response to the level of the second signal, and the source / drain path of the first MOS transistor is changed in accordance with the level of the first signal. The first current flows through it, When the semiconductor integrated circuit device is in the first state, the input control circuit controls the level of the first signal to a predetermined level regardless of the level of the first signal in the second state. At the same time, the switch is turned off in response to the level of the second signal, When the first operating potential point is a potential higher than the second operating potential point, the first MOS transistor is a P-channel MOS transistor, and the predetermined level is set to a high level, and the second operating potential point is the first operating potential point. And the first MOS transistor is an N-channel MOS transistor when the potential is higher than a dot, and the predetermined level is set at a low level. The method of claim 6, The switch includes a second MOS transistor having a source / drain path between the first node and the first operating potential point, and the second MOS transistor is of the same conductivity type as the first MOS transistor. A semiconductor integrated circuit device. delete The method of claim 6 or 8, A third MOS transistor whose source is connected to the second node and whose drain is connected to the drain of the first MOS transistor and receives the first signal; And a conductivity type of the third MOS transistor and a conductivity type of the first MOS transistor. delete delete delete delete delete delete delete delete delete delete The method according to claim 1 or 2, When the control signal is in the first state, the first current flows through a source / drain path of the first MOS transistor in an on state, and when the control signal is in the second state, the first state is off. And a sub-threshold current flowing through the source / drain path of the first MOS transistor to the second current. The method of claim 4, wherein When the control signal is in the first state, the first current flows through a source / drain path of the first MOS transistor in an on state, and when the control signal is in the second state, the first state is off. And a sub-threshold current flowing through the source / drain path of the first MOS transistor to the second current. The method of claim 6, In the first state, the first current flows through the source / drain path of the first MOS transistor in the on state, and in the second state, the source and drain of the first MOS transistor in the off state. And limiting the subthreshold current flowing through the path to a second current smaller than the first current.