SEMICONDUCTOR INTEGRATED CIRCUITS

1 . A semiconductor integrated circuit comprising:

a first power source wiring line supplying a first supply voltage;

a logic circuit block which is operable by being supplied with the first supply voltage;

a second power source wiring line supplying a second supply voltage which is higher in level than the first supply voltage;

a switch which is capable of connecting the first power source wiring line and the second power source wiring line; and

a control circuit controls said switch when the first supply voltage has undergone a potential drop, so as to intermittently connect said second power source wiring line to said first power source wiring line.

2 . A semiconductor integrated circuit according to claim 1 , further comprising

a voltage measurement circuit which is capable of measuring a fluctuation of the first supply voltage,

wherein said control circuit controls said switch in accordance with a measured result in said voltage measurement circuit.

3 . A semiconductor integrated circuit according to claim 2 ,

wherein said voltage measurement circuit comprises:

a ring oscillator which is capable of converting voltage information into oscillation cycle information; and

an analog/digital conversion circuit which converts the oscillation cycle information of said ring oscillator into a digital signal; and

wherein said second power source wiring line is intermittently connected to said first power source wiring line in accordance with the output signal of said analog/digital conversion circuit.

4 . A semiconductor integrated circuit according to claim 1 ,

wherein when the first supply voltage and the second supply voltage are supplied from a voltage feed circuit which is provided at outside said semiconductor integrated circuit, a time constant of the control in the case of intermittently connecting said second power source wiring line to said first power source wiring line is set to be smaller than a voltage-control time constant of said voltage feed circuit.

5 . A semiconductor integrated circuit according to claim 1 , wherein said switch comprises a MISFET.

6 . A semiconductor integrated circuit according to claim 5 ,

wherein said MISFET is intermittently rendered conductive in a case where the output signal of said analog/digital conversion circuit is larger than a preset voltage fluctuation magnitude.

7 . A semiconductor integrated circuit according to claim 1 ,

wherein said switch comprises MISFETs which are divided into a plurality of groups, and reference levels which are different from one another are set for the respective groups, whereby the intermittent connections between said second power source wiring line and said first power source wiring line are controlled in units of the groups.

8 . A semiconductor integrated circuit according to claim 1 ,

wherein said control circuit comprises the same sort of MISFET as a MISFET constituting said logic circuit block.

9 . A semiconductor integrated circuit according to claim 1 ,

wherein all MISFETs constituting said control circuit are the same sort of MISFETs as MISFETs constituting said logic circuit block.

10 . A semiconductor integrated circuit according to claim 1 ,

wherein said control circuit comprises a MISFET which is different in a gate insulating film thickness from a MISFET constituting said logic circuit block.

11 . A semiconductor integrated circuit according to claim 1 , further comprising

a thermometer which is capable of measuring a temperature within said semiconductor integrated circuit,

wherein the control by said control circuit is limited on the basis of a measured result of said thermometer.

12 . A semiconductor integrated circuit according to claim 11 ,

wherein the control by said control circuit is not performed in a case where the measured result of said thermometer exceeds a predetermined level.

13 . A semiconductor integrated circuit according to claim 1 ,

wherein said first power source wiring line is lower in impedance than said second power source wiring line and is connected using a large number of wiring lines, and said second power source wiring line is wired with the number of wiring lines smaller than the number of the wiring lines of said first power source wiring line.

14 . A semiconductor integrated circuit according to claim 3 , further comprising:

a digital filter which executes a filtering process of the output signal of said analog/digital conversion circuit.

15 . A semiconductor integrated circuit according to claim 1 ,

wherein when said first power source wiring line and said second power source wiring line are arrayed in a direction orthogonal to an arrayal direction of logic cells, said switch is integrated in an arrayed region of said first power source wiring line and said second power source wiring line.

16 . A semiconductor integrated circuit according to claim 1 ,

wherein said switch is driven by a pulse-shaped signal, and a pulse width and a pulse interval of the pulse-shaped signal are controlled by said control circuit.

17 . A semiconductor integrated circuit according to claim 2 ,

wherein said semiconductor integrated circuit is separated into a plurality of power source regions which can be controlled independently of one another as to whether or not feed of an operating voltage is cut off,

wherein said plurality of power source regions has a common power source region which is energized even in a case where the feed of the operating voltage is controlled so as to be cut off,

wherein the voltage measurement circuits are respectively arranged in said plurality of power source regions,

wherein the control circuits are collectively arranged in a region which is different from said plurality of power source regions, and

wherein signals which are transferred between said control circuits and said voltage measurement circuits are transferred through said common power source region of said plurality of power source regions.