Integrated circuit, integrated circuit design device and integrated circuit design method

The disclosed integrated circuit includes a first and a second power supply wirings, a flip-flop circuit, and a switch element. The first and the second power supply wirings are connected to the common power supplies. The flip-flop circuit is required to hold the stored data even when the voltage supply from the power supplies to the integrated circuit is stopped. The flip-flop circuit is connected to the first power supply wiring. The switch element is a transistor, for example, and switches whether or not the voltage is supplied from the power supplies. The switch element is provided on the second power supply wiring.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2010-131271, filed on Jun. 8, 2010, the entire contents of which are incorporated herein by reference.

FIELD

This invention relates to an integrated circuit in which flip-flop circuits are arranged.

BACKGROUND

Recently, there appears an integrated circuit (LSI) loading plural cells on a single chip. In the integrated circuit of this kind, there is such a problem that the electric power consumption increases due to the increase of the circuit scale. Therefore, it is considered to decrease the voltage supplied to the integrated circuits which are not used, thereby achieving conservation of electric power.

When the voltage supplied to the integrated circuit is decreased, there is a case that the flip-flop circuits arranged in the integrated circuit are required to hold the data stored inside. Therefore, it is conceived that the power supplies are separately provided for the flip-flop circuits required to hold the data and the cells other than those flip-flop circuits (See. Japanese Laid-open Patent Applications No. 2006-210841 and No. 2005-157487).

However, when the power supplies are separately provided as described above, the number of the power supplies increases, and there is an anxiety that the chip size increases.

SUMMARY

The disclosed integrated circuit includes a first and a second power supply wirings connected to common power supplies; a flip-flop circuit connected to the first power supply wiring; and a switch element which is provided on the second power supply wiring and which switches whether or not to supply voltage from the power supplies.

The disclosed integrated circuit includes a first and a second power supply wirings, a flip-flop circuit, and a switch element. The first and the second power supply wirings are connected to the common power supplies. The flip-flop circuit is required to hold the stored data even when the voltage supply from the power supplies to the integrated circuit is stopped. The flip-flop circuit is connected to the first power supply wiring. The switch element is a transistor, for example, and switches whether or not the voltage is supplied from the power supplies. The switch element is provided on the second power supply wiring.

According to the disclosed integrated circuit, since the power supplies which supply the voltage to the first and the second power supply wirings are provided in common, the number of the power supplies can be reduced and the increase of the chip size can be suppressed.

DESCRIPTION OF EMBODIMENT

An example of an embodiment will be described below with reference to the attached drawings.

First, the description will be given of an example of a hardware configuration of an integrated circuit design device200according to the embodiment.

FIG. 1shows an example of a hardware configuration of the integrated circuit design device200. The integrated circuit design device200is a computer such as a PC (Personal Computer), for example, and includes a control unit11, a memory12, a hard disk13, an output unit14, an input unit15, an interface (I/F)16and a disk drive17. These constitutional elements are connected to a bus10. The control unit11is a CPU (Central Processing Unit), for example. The memory12is a ROM (Read Only Memory) or a RAM (Random Access Memory), for example. The output unit14is an output device such as a monitor and a printer, and the input unit15is an input device such as a mouse and/or a keyboard. The interface16is an external connection interface such as a USB (Universal Serial Bus). The disk drive17is a disk drive for driving a disk such as a DVD (Digital Versatile Disc).

In the integrated circuit design device200, the control unit11executes a program based on the instruction from the user. Thus, the integrated circuit according to the embodiment is designed based on the data inputted by the user. The integrated circuit according to the embodiment will be described below.

First, prior to explaining the integrated circuit according to the embodiment, an integrated circuit according to a comparative example will be described with reference toFIGS. 2 and 3. The integrated circuit described below is designed such that, even when the voltage supply from the power supply is stopped, the voltage is supplied to the flop-flop circuit which is required to hold the data.

FIG. 2is an example of a layout block diagram of an integrated circuit100R using a flip-flop circuit having two power supply terminals including a power supply terminal for data holding and a power supply terminal for normal operation (hereinafter referred to as “two power supply flip-flop circuit”) The power supply terminal for normal operation is a terminal for supplying voltage to all elements in the two power supply flip-flop circuit. The power supply terminal for data holding is a terminal for supplying voltage only to the elements associated with the data holding in the two power supply flip-flop circuit.

In the integrated circuit100R shown inFIG. 2, the flip-flop circuits RFF1, RFF2are the two power supply flip-flop circuits. The power supply wiring F_VDD1is a wiring connected to the power supply terminal Tm1for normal operation in the two power supply flip-flop circuit and the power supply terminal of the cells (not shown) other than the two power supply flip-flop circuit. Both ends of the power supply wiring F_VDD1are connected to the power supply VDD1. The power supply wiring F_VDD2is a wiring to which the power supply terminal Tm2for data holding of the two power supply flip-flop circuit is connected. Both ends of the power supply wiring F_VDD2are connected to the power supply VDD2. The power supply wiring F_VSS is a wiring connected to the ground terminal of all cells. Both ends of the power supply wiring F_VSS are connected to the power supply VSS set to ground (0V), for example.

As shown inFIG. 2, in the integrated circuit100R, in order to supply the voltage to the power supply terminal Tm2for data holding, the wiring is drawn out from the power supply wiring F_VDD2to the power supply terminal Tm2, Therefore, in the integrated circuit100R, there is an anxiety that the efficiency of wiring is deteriorated and the chip size is increased.

FIG. 3is an example of a layout block diagram of an integrated circuit100L in which the power supplies for supplying voltage are separately provided for the flip-flop circuits required to hold the data and the cells other than those flip-flop circuits.

InFIG. 3, the flip-flop circuits FF1, FF2are the flip-flop circuits which are required to hold the data stored inside. Different from the flip-flop circuits shown inFIG. 2, the flip-flop circuits FF1, FF2are not provided with the power supply terminals for holding data.

The power supplies VDD2are dedicated power supplies to supply the voltage to the flip-flop circuits FF1, FF2. The power supplies VDD2are arranged in parallel with each other, and plural power supply wirings F_VDD2are arranged to connect the power supplies VDD2. To the power supply wirings F_VDD2, the power supply terminals (i.e., the power supply terminals for normal operation) of the flip-flop circuits FF1, FF2are connected. The power supplies VDD are the power supplies which supply the voltage to the cells (not shown) other than the flip-flop circuits FF1, FF2. The power supplies VDD are arranged in parallel with each other, and plural power supply wirings F_VDD are arranged to connect the power supplies VDD. To the power supply wirings F_VDD, the power supply terminals of the cells other than the flip-flop circuits FF1, FF2are connected. To the power supplies VDD, the power supply wirings F_VSS are connected. The power supplies VSS are arranged in parallel with each other, and plural power supply wirings F_VSS are arranged to connect the power supplies VSS. To the power supply wirings F_VSS, the ground terminal of all cells are connected. The power supply wirings F_VDD and the power supply wirings F_VSS are alternately arranged.

The control circuit for controlling the integrated circuit100L holds the voltage of the power supplies VDD2and decreases the voltage of the power supplies VDD when the voltage supplied to the integrated circuit100L is decreased. By this, the voltage supplied to the cells other than the flip-flop circuits FF1, FF2can be decreased, while holding the voltage supplied to the flip-flop circuits FF1, FF2. Thus, even when the voltage supplied to the integrated circuit100L is decreased, the data stored in the flip-flop circuits FF1, FF2can be held. However, since the power supplies VDD2for data holding are provided in addition to the power supplies VDD in the integrated circuit100L, there is an anxiety that the chip size increases.

In this view, in the integrated circuit according to the embodiment, the power supplies for supplying the voltage are provided in common, for the flip-flop circuits required to hold the data and the other cells, and the power supply wirings to supply the voltage to the other cells are provided with switch elements. The description will be specifically given below with reference toFIG. 4.

FIG. 4shows an example of a layout block diagram of an integrated circuit100according to the embodiment. InFIG. 4, the constitutional elements identical to those shown in FIG.3are indicated by the identical reference signs.

As shown inFIG. 4, in the integrated circuit100, two power supply wirings F_VDD and one power supply wiring F_VDD2are connected to the common power supplies VDDp. Specifically, the power supplies VDDp are provided in parallel with each other, and the power supply wirings F_VDD, F_VDD2are arranged to connect the power supplies VDDp. In addition, the power supplies VSS are arranged in parallel with each other, and the power supply wirings F_VSS are arranged to connect the power supplies VSS. The power supply wirings F_VDD, F_VDD2and the power supply wirings F_VDD are alternately arranged.

The flip-flop circuits FF1, FF2required to hold the data are arranged along the power supply wirings F_VDD2. The cells (not shown) other than the flip-flop circuits FF1, FF2are arranged along the power supply wirings F_VDD. Further, the switch elements SW1to SW4such as transistors are provided to the power supply wirings F_VDD. These switch elements are provided to switch the supply of voltage from the power supplies VDDp to the power supply wirings F_VDD. Specifically, the switch elements are provided at both ends of the power supply wirings F_VDD in order to control the supply of the voltage from each of the two power supplies VDDp connected to both ends of the power supply wirings F_VDD. In the example shown inFIG. 4, out of the two power supply wirings F_VDD, one power supply wiring F_VDD is provided with the switch elements Sw1, Sw2at both ends, and the other power supply wiring F_VDD is provided with the switch elements Sw3, SW4at both ends. As is understood from this, the power supply wiring F_VDD2functions as the first power supply wiring, and the power supply wiring F_VDD functions as the second power supply wiring.

When the voltage supplied to the integrated circuit100is decreased, the control circuit controlling the integrated circuit100switches the switch elements SW1to Sw4and stops the supply of the voltage from the power supplies VDDp to the power supply wiring F_VDD. At that time, the voltage from the power supplies VDDp is still supplied to the power supply wiring F_VDD2. In this way, similarly to the description ofFIG. 3, the power supply voltages supplied to the cells other than the flip-flop circuits FF1, FF2can be decreased, while holding the voltage supplied to the flip-flop circuits FF1, FF2. In comparison with the integrated circuit100L shown inFIG. 3, in the integrated circuit100according to the embodiment, the power supplies for supplying the voltage are provided in common for the flip-flop circuits and the cells other than the flip-flop circuits. Therefore, in comparison with the integrated circuit100L, the integrated circuit100according to the embodiment can reduce the number of the power supplies and can suppress the increase of the chip size.

Next, integrated circuits of other examples according to the embodiment will be described with reference toFIGS. 5 and 6.

FIG. 5shows an example of a layout block diagram of an integrated circuit100aaccording to another example of the embodiment. InFIG. 5, the constitutional elements identical to those shown inFIG. 4are indicated by the identical reference signs.

In the integrated circuit100shown inFIG. 4, the plural power supply wirings are arranged to connect the power supplies VDDp. In contrast, in the integrated circuit according to another example of the embodiment, at least one power supply wiring out of the plural power supply wirings connecting the power supplies VDDp is cut, and one wiring of the power supply wiring thus cut is used as the power supply wiring F_VDD2while the other wiring is used as the power supply wiring F_VDD. Namely, the integrated circuit according to another example of the embodiment includes the power supply wiring F_VDD2having one end connected to the power supply VDDp and the other end cut, and the power supply wiring F_VDD having one end connected to the power supply VDDp and the other end cut. For example, in the integrated circuit100ashown inFIG. 5, out of the plural power supply wirings connecting the power supplies VDDp, one power supply wiring is cut, and one wiring of the power supply wiring thus cut is used as the power supply wiring F_VDD2while the other wiring thereof is used as the power supply wiring F_VDD. To the power supply wiring F_VDD2, the flip-flop circuits FF1, FF2are connected. At one end of the power supply wiring F_VDD, the switch element SW5is provided.

When the voltage supplied to the integrated circuit100ais decreased, the control circuit controlling the integrated circuit100aswitches the switch elements SW1to SW5to stop the supply of the voltage from the power supplies VDDp to the power supply wirings F_VDD. In this way, similarly to the case ofFIG. 4, the power supply voltage supplied to the cells other than the flip-flop circuits FF1, FF2can be decreased, while holding the voltage supplied to the flip-flop circuits FF1, FF2. In the following description, the flip-flop circuits required to hold the data are referred to as “flip-flop circuit FF”, and the switch elements are referred to as “switch elements SW”.

FIG. 6shows an example of a layout block diagram of an integrated circuit100baccording to another example.

As shown inFIG. 6, in the integrated circuit100b, two power supply wirings out of the plural power supply wirings connecting the power supplies VDDp are cut, and one wiring of each of the power supply wirings thus cut is used as the power supply wirings F_VDD2while other wiring of each of the power supply wirings thus cut are used as the power supply wirings F_VDD. To the power supply wirings F_VDD2, the plural flip-flop circuits FF are connected. In addition, the switch elements SW are provided on the power supply wirings F_VDD.

As is understood from the above description, also in the integrated circuits100a,100bshown inFIGS. 5 and 6, the power supplies for supplying the voltage is provided in common for the flip-flop circuits and the cells other than the flip-flop circuits. Therefore, by the integrated circuits100a,100bshown inFIGS. 5 and 6, similarly to the integrated circuit100according to the embodiment, the number of the power supplies can be reduced, and the increase of the chip size can be suppressed. In addition, the integrated circuits100a,100bincludes the power supply wiring F_VDD2having one end connected to the power supply VDDp and the other end cut, and the power supply wiring F_VDD having one end connected to the power supply VDDp and the other end cut, and the power supply wiring F_VDD is provided with the switch element. With this configuration, as shown inFIG. 6, the flip-flop circuits can be arranged in a manner concentrated on one side of the two sides where the power supplies are arranged in the integrated circuit.

Next, the integrated circuit design method executed by the integrated circuit design device200will be described with reference to the flowchart ofFIG. 7.FIG. 7is the flowchart showing the design process of designing the integrated circuit according to the embodiment. The design process shown inFIG. 7is achieved by the control unit11executing the program in the integrated circuit design device200.

First, in step S101, the control unit11produces a net list based on the circuit diagram inputted by the user. In next step S102, the number of the flip-flop circuits FF arranged to be on the substrate of the integrated circuit is inputted by the user.

In step S103, the control unit11calculates the arrangement area where the flip-flop circuits FF are arranged, based on the number of the flip-flop circuits FF and the size of the flip-flop circuits FF. This calculation method will be specifically described with reference toFIG. 8.

FIG. 8is an enlarged view of the flip-flop circuit FF arranged along the power supply wiring F_VDD2. InFIG. 8, the length of the flip-flop circuit FF along the power supply wiring F_VDD2is expressed by Y1, and the length thereof in the direction orthogonal to the power supply wiring F_VDD2is expressed by Y2.

The control unit11calculates the total length L of the power supply wirings F_VDD2required in the integrated circuit, based on the number N of the flip-flop circuits FF. The total length L of the power supply wirings F_VDD2can be calculated by the following equation (1). Here, the reason why diving by 2 is that two flip-flop circuits FF can be arranged symmetrically with respect to one power supply wiring F_VDD2as shown inFIG. 8.
L=(N×Y1)/2  (1)

When the control unit11calculates the total length L of the power supply wirings F_VDD2by the equation (1), the control unit11then calculates the width of the area where the flip-flop circuits FF are arranged, based on the length pL per one power supply wiring F_VDD2. As is previously shown, compared with the length per one power supply wiring F_VDD2shown inFIG. 3, the length per one power supply wiring F_VDD2shown inFIG. 4is short. The control unit11can calculate the necessary number of the power supply wirings F_VDD2having the length pL, by dividing the length L obtained by using the equation (1) by the length pL. The necessary number of the power supply wirings F_VDD2thus obtained and the length pL of the power supply wiring F_VDD2show the arrangement area where the flip-flop circuits FF are arranged.

In this way, the control unit11calculates the arrangement area of the flip-flop circuits FF based on the length pL of the flip-flop circuits FF and the number of the flip-flop circuits FF.

Returning to the flowchart ofFIG. 7, in step S104, the control unit11performs the design of the power supply wirings of the flip-flop circuits FF, specifically the design of arranging the power supply wirings F_VDD2on the substrate, based on the arrangement area where the flip-flop circuits FF are arranged. Further, the control unit11performs the design of arranging the power supply wirings F_VDD, F_VSS on the substrate and connecting the power supply wirings F_VDD, F_VDD2to the power supplies VDDp, and performs the design of providing the switch elements to the power supply wirings F_VDD. Then, the control unit11goes to the process in step S105.

In step S105, the control unit11performs the design of arranging the flip-flop circuits FF along the power supply wirings F_VDD2, and performs the design of arranging the cells other than the flip-flop circuits FF along the power supply wirings F_VDD. Then, the control unit11performs the wiring of connecting each cell and the power supply wiring. For example, the control unit11performs the design of forming the wiring between the flip-flop circuits FF and the power supply wirings F_VDD2, and performs the design of forming the wiring between the cells other than the flip-flop circuits FF and the power supply wirings F_VDD. Then, the control unit goes to the process of step S106.

In step S106, the control unit11performs the delay calculation, and performs the timing adjustment such that the integrated circuit designed by the step S106satisfies the required timing conditions. Then, the control unit11ends this design process. In this way, the design of the integrated circuit is completed.

Summarizing the above, in the integrated circuit design device200, the control unit11calculates the arrangement area where the flip-flop circuits FF are arranged, based on the number of the flip-flop circuits FF and the size of the flip-flop circuits FF to be arranged on the substrate. Then, the control unit11performs the design of arranging the power supply wirings F_VDD, F_VDD2on the substrate and connecting the power supply wirings F_VDD, F_VDD2to the common power supplies VDDp, based on the arrangement area thus calculated. Here, the control unit11performs the design of providing the switch elements to the power supply wirings F_VDD. Then, the control unit11performs the design of arranging the flip-flop circuits on the substrate along the power supply wirings F_VDD2. Therefore, the control unit11function as the arrangement area calculating unit, the power supply wiring designing unit and the flip-flop circuits arrangement designing unit. Thus, the integrated circuit according to the embodiment is designed.

MODIFIED EXAMPLE

Next, a modified example of the integrated circuit according to the above-described embodiment will be described. As shown inFIGS. 4 to 6, in the integrated circuit according to the embodiment, the power supply wirings F_VDD2are provided in parallel with the power supply wirings F_VDD. In contrast, in the integrated circuit according to the modified example, the power supply wirings F_VDD2are provided orthogonally to the power supply wirings F_VDD. It will be specifically described below with reference toFIG. 9.

In the integrated circuit100caccording to the modified example, the power supplies VDDp, VSS are provided in the rectangular shape, and the power supply wirings are provided in a mesh fashion inside the area surrounded by the power supplies VDDp, VSS. Specifically, on the upper layer of the plural power supply wirings provided in parallel with each other, in a manner orthogonal to those plural power supply wirings, other plural power supply wirings are further provided in parallel with each other.FIG. 9shows an example of the integrated circuit in the case that the power supply wirings are provided in a double-layer structure. In the integrated circuit100cshown inFIG. 9, the power supply wirings connected to the power supply VDDp are the power supply wirings F_VDD in the lower layer, and the power supply wiring connected to the power supply VDDp is the power supply wiring F_VDD2in the upper layer. Namely, the power supply wiring F_VDD2is orthogonal to the power supply wirings F_VDD. Needless to say, while only one power supply wiring F_VDD2is shown in the upper layer, plural power supply wirings F_VDD2are actually provided orthogonally to the power supply wirings F_VDD in the lower layer. To each of the power supply wirings F_VDD, the switch elements SW for controlling whether or not the voltage is supplied from the power supply VDDp is provided.

At the intersections P1, P2, the power supply wiring F_VDD2is in contact with the wirings F_V1, F_V0which are provided in the lower layer and which are cut from the power supply VDDp at both ends. Therefore, the wirings F_V1, F_V2also function as the power supply wiring F_VDD2. The flip-flop circuits FF are provided along the wirings F_V1, F_V2and are connected to the wirings F_V1, F_V2.

The integrated circuit design device200can design the integrated circuit100caccording to the modified embodiment by executing the same process as described with the flowchart shown inFIG. 7. However, since the power supply wirings F_VDD2are orthogonal to the power supply wirings F_VDD, the total length L of the power supply wirings F_VDD2is calculated by the following equation (2) (see.FIG. 8).
L=(N×Y2)/2  (2)

Similarly to the integrated circuit according to the above-described embodiment, by the integrated circuit100caccording to the modified example, the power supplies are provided in common for the power supply wirings to which the flip-flop circuits are connected and the power supply wirings to which the cells other than the flip-flop circuits are connected. Therefore, by the integrated circuit100caccording to the modified example, the number of power supplies can be reduced, and the increase of the chip size can be suppressed.