JP2000124785A - Semiconductor integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform stable operation of a circuit group constituted of the MOSFET of a low threshold voltage for performing a low voltage operation, thus realizing lower power consumption (to reduce a leakage current). SOLUTION: This semiconductor integrated circuit is provided with the signal level maintaining means S1 and S2 of different level maintenance respectively in the output parts of the respective circuit groups A, B, C and D so as to make the output of the respective circuit groups A, B, C and D at the shifting to an active operation from a standby state have the same logical level as the one at the shifting to the standby state from the active operation. A supply voltage Vcca supplied to the circuit groups A, B, C and D at the time of standby T2 is lowered to a level close to a ground potential Vss by the leakage current of the circuit groups A, B, C and D, however, the signal level maintaining means S1 and S2 maintain the respective output (a), (b), (c) and (d) of the circuit groups A, B, C and D at the levels of H (high), L (low), H and H when the output of the respective circuit groups A, B, C and D is shifted from the active operation to the standby state.

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 which realizes stable operation and low power consumption (reduction of leakage current) in a circuit group composed of low threshold voltage MOSFETs for performing low voltage operation. It is related to the circuit.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional technique for realizing low power consumption (reduction of leak current) in a circuit group composed of MOSFETs having a low threshold voltage for performing a low voltage operation. See JP-A-8-321763).

[0003] In the prior art shown in FIG.
The circuit groups A, B, C, and D composed of OSFETs have an internal power supply terminal Vcca and an external power supply Vcc connected to the power control means SW.
1 are connected. This power control means SW1
Is turned on when active, connects the external power supply Vcc to the internal power supply terminals Vcca of the selected circuit groups A, B, C, and D, and turns off and disconnects these connections during standby.

[0004]

However, when the power control means SW1 is in a standby state, the voltage Vcca supplied to the circuit group A, B, C or D to be connected is reduced by the leakage current of the circuit group due to the ground potential. It drops to a level close to Vss.

For this reason, the outputs a, b, c, and d of the circuit groups A, B, C, and D become low level, and there is a problem that a malfunction occurs when the active operation is started.

That is, as shown in FIG. 6, when a transition is made from the active state T1 to the standby state T2, for example, the inputs a and b to the circuit group C are high level (H) and low level (L). Assuming that the signals c and d are H and H, the signals a, c and d are close to the ground potential with a decrease in the voltage Vcca supplied to the circuit groups A, B, C or D, and It becomes logically L (the logical level changes).

Thereafter, when the circuit group D has a function of latching the output c of the circuit group C when the active state T3 is restored, if the function of the circuit group C is delayed,
A signal (L) different from the normal signal (H) is taken in, which may cause a malfunction.

This is because the circuit groups A, B,
This is because all the outputs a, b, c, and d of C and D become low level.

An object of the present invention is to provide a circuit group composed of MOSFETs having a low threshold voltage for performing a low-voltage operation, thereby achieving stable operation and low power consumption (reduction of leakage current).
It is to provide a semiconductor integrated circuit which realizes the above.

[0010]

In order to achieve the above object, a semiconductor integrated circuit according to the present invention is a semiconductor integrated circuit having a circuit group composed of MOSFETs having a low threshold voltage for performing a low voltage operation. Signal level maintaining means, wherein the signal level maintaining means maintains the output of each circuit group when entering the active operation from the standby state at the same logic level as when entering the standby state from the active operation. .

In addition, the deactivation of the signal level maintaining means when shifting from the standby state to the active operation includes:
This is performed after the voltage supplied from the external power supply to the circuit group rises to such an extent that it is recognized as the H level.

Further, the signal level maintaining means is selectively provided in a part of a circuit group included in the semiconductor integrated circuit.

The signal level maintaining means is provided in each circuit group included in the semiconductor integrated circuit.

Further, the signal level maintaining means includes a MOS
It is composed of an FET, and the threshold value of the MOSFET is set high.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing a semiconductor integrated circuit according to one embodiment of the present invention, FIG. 2 is a waveform diagram showing the operation of the semiconductor integrated circuit according to one embodiment of the present invention, and FIG. FIG. 4 is a configuration diagram illustrating a power control unit used in a semiconductor integrated circuit according to an embodiment of the present invention, and FIG. 4 is a configuration diagram illustrating a signal level maintaining unit used in a semiconductor integrated circuit according to an embodiment of the present invention.

FIG. 1 shows a semiconductor integrated circuit according to an embodiment of the present invention, in which circuit groups A, B, C, and D composed of low threshold voltage MOSFETs are cascaded. B, C and D indicate that the internal power supply terminal Vcca is
cc is connected in parallel via power control means SW1. Here, the circuit groups A, B, C, and D composed of low threshold voltage MOSFETs have an output level of H during standby.
Or, it means an aggregate of circuits fixed to one of L, and includes not only a combinational circuit but also a sequential circuit typified by a flip-flop or a latch circuit.

The power control means SW1 is turned on when it is active, and the external power supply Vcc and the selected circuit groups A, B,
The internal power supply terminals Vcca of C and D are connected and turned off during standby to cut off these connections. Specifically, as shown in FIG. 3, the power control means SW1
It is configured by an OSFET, and is switched between a standby state and an active state based on a control signal PD input to the gate.

Further, in the embodiment of the present invention, as shown in FIG. 1, the outputs of the circuit groups A, B, C, and D when entering the active operation from the standby state are the same as when entering the standby state from the active operation ( Each circuit group A, B, C,
The output section of D has signal level maintaining means S1 and S2 having different level maintenance. When the signal level maintaining means S1 and S2 are deactivated at the time of transition from the standby state to the active operation, the voltage supplied from the external power supply Vcc to the circuit groups A, B, C and D is recognized as the H level. It is designed to be performed after rising to the extent. Also,
The signal level maintaining means S1, S2 may be selectively provided in some of the circuit groups A, B, C, D included in the semiconductor integrated circuit, and the signal level maintaining means S1, S2 may be provided in the semiconductor integrated circuit. May be provided for each of the circuit groups A, B, C, and D included in.

The signal level maintaining means S1 maintains the output signal level at L in standby mode.
The signal level maintaining means S1 is connected to the output side of the circuit group B.

The signal level maintaining means S2 maintains the output signal level at H at the time of standby,
The signal level maintaining means S2 is connected to each output side of the circuit groups A, C, D.

Specifically, as shown in FIG. 4A, the signal level maintaining means S1 comprises three transistors 1, 2, 3 connected in series, and an output control transistor 4.

The three transistors 1, 2, 2, 3 connected in series
3, the control signal PD is applied to the gate of the transistor 1.
And an external power supply Vcc is connected to its drain,
An output signal b from the circuit group B is input to each gate of the transistors 2 and 3.

In the output control transistor 4, the source is commonly connected to the drain of the transistor 2 and the source of the transistor 3, and the control signal PD is input to the gate.

Further, the signal level maintaining means S2 is provided as shown in FIG.
As shown in (b), the transistor is composed of three transistors 5, 6, 7 connected in series and an output control transistor 8.

The three transistors 5, 6, connected in series
7, the control signal PD is applied to the gate of the transistor 7.
(PD bar) is input. The sources of the transistors 5 and 6 are connected to the external power supply Vc.
c is connected, and the output signals a, c, or d from the circuit groups A, C, or D are input to the gates of the transistors 5, 6, respectively.

In the output control transistor 8, the drain of the transistor 5 and the drain of the transistor 6 are connected in common, and the gate thereof receives the inverted signal of the control signal PD (PD bar).

Therefore, as shown in FIG. 4, the signal level maintaining means S1 receives the control signal P inputted for power control.
Based on D, the L level is maintained during standby. Further, as shown in FIG. 4, the signal level maintaining means S2 maintains the H level during standby based on an inverted signal (PD bar) of the control signal PD input for power control.

Here, a circuit group (A, B, C, D) whose output level at the time of standby is L level is provided with a signal level maintaining means S1 for maintaining the output signal level at the time of standby at L level. The output level during standby is H
The circuit group (A, B, C, D) which is a level is provided with a signal level signal level maintaining means S1 for maintaining the output signal level at the time of standby at H level.

The operation in the embodiment of the present invention will be described. In the conventional case shown in FIG.
When the transition from 1 to the standby state T2 occurs, for example, the inputs a and b to the circuit group C are high level (H) and low level (L).
Assuming that the signals c and d are H and H in response, the voltage V supplied to the circuit group A, B, C or D
As the cca decreases, the signals a, c, and d become closer to the ground potential and become logically L (the logical level changes).

Thereafter, when it is assumed that the circuit group D has a function of latching the output c of the circuit group C when the active state T3 is restored again, if the operation of the circuit group C is delayed, etc.
A signal (L) different from the normal signal (H) is taken in, which may cause a malfunction.

On the other hand, in the embodiment of the present invention, the output of each of the circuit groups A, B, C and D at the time of entering the active operation from the standby state has the same logic level as at the time of entering the standby state from the active operation. As shown, the output units of the circuit groups A, B, C, D have signal level maintaining means S1, S2 having different level maintenance, respectively.

At the time of standby T2, the circuit groups A, B, C, D
Is supplied to the circuit groups A, B, C,
Although the level is reduced to a level close to the ground potential Vss due to the leakage current of D, the signal level maintaining means S1 and S2 in the embodiment of the present invention switch the outputs of the circuit groups A, B, C and D from the active operation to the standby state. At the time of transition, the outputs a, b, c, d of the circuit groups A, B, C, D are set to H, L,
Maintain H, H levels.

Therefore, the same signal level as in the standby state in the normal operation can be obtained, and the outputs a, b, c, d of the circuit groups A, B, C, D immediately before the transition to the active operation T3 are H, L, H, and H. Therefore, a malfunction does not occur when the active operation is started as shown in the conventional example.

[0035]

As described above, according to the present invention, the output of each circuit group when entering the active operation from the standby state is the same logic (that does not cause a malfunction) as when entering the standby state from the active operation. The level can be set, and stable operation without causing malfunction and low power consumption (reduction of leak current) can be realized.

The deactivation (control signal PD off) of the signal level maintaining means at the time of transition from the standby state to the active operation is performed when the voltage supplied from the external power supply to the circuit group is recognized as H level. To do after rising
That is, a malfunction can be prevented by delaying the deactivation.

Further, by selectively providing the signal level maintaining means in a part of the circuit group included in the semiconductor integrated circuit, effective application can be realized and an increase in circuit scale can be avoided. Further, by providing the signal level maintaining means in each circuit group included in the semiconductor integrated circuit, the circuits can be integrated, and the circuit can be simplified by assembling and combining.

Further, the MO constituting the signal level maintaining means is
By setting the threshold of the SFET high, the standby current can be further reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a semiconductor integrated circuit according to an embodiment of the present invention.

FIG. 2 is a waveform chart showing an operation of the semiconductor integrated circuit according to one embodiment of the present invention.

FIG. 3 is a configuration diagram showing power control means used in the semiconductor integrated circuit according to one embodiment of the present invention.

FIG. 4 is a configuration diagram showing a signal level maintaining means used in the semiconductor integrated circuit according to one embodiment of the present invention.

FIG. 5 is a configuration diagram showing a semiconductor integrated circuit according to a conventional example.

FIG. 6 is a waveform chart showing an operation of a semiconductor integrated circuit according to a conventional example.

[Explanation of symbols]

 A, B, C, D circuit groups S1, S2 Signal level maintaining means

Claims (5)

[Claims] 1. A semiconductor integrated circuit having a circuit group composed of MOSFETs having a low threshold voltage for performing a low-voltage operation, comprising: a signal level maintaining unit; A semiconductor integrated circuit wherein the output of each circuit group at the time of entering the active operation is maintained at the same logic level as at the time of entering the standby state from the active operation. 2. Deactivating the signal level maintaining means when shifting from a standby state to an active operation is performed after a voltage supplied to a circuit group from an external power supply rises to an extent that it is recognized as an H level. The semiconductor integrated circuit according to claim 1, wherein: 3. The semiconductor integrated circuit according to claim 1, wherein said signal level maintaining means is selectively provided in a part of a circuit group included in the semiconductor integrated circuit. 4. The semiconductor integrated circuit according to claim 1, wherein said signal level maintaining means is provided in each circuit group included in the semiconductor integrated circuit. 5. The signal level maintaining means includes a MOSFE.
2. The semiconductor integrated circuit according to claim 1, wherein the semiconductor integrated circuit is constituted by T and the threshold value of the MOSFET is set high.