US 7,002,834 B2Granted

Semiconductor integrated circuit

AssigneeFujitsu Limited

InventorWataru Yokozeki

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Abstract

At switching normal operation mode to low power mode, a first switch disconnects a virtual power supply line and a normal power supply line in response to activation of a switch control signal. The power supply voltage to a first circuit block connected to the virtual power supply line is suspended during the low power mode. A second switch of a floating prevention circuit connects a node between output of the first circuit block and input of a second circuit block to a first voltage line in response to inactivation of the switch control signal during the low power mode. This prevents the input of the second circuit block from floating even without the power supply voltage supplied to the first circuit block, and therefore prevents feedthrough current from flowing through the second circuit block, which enables reduction in power consumption during the low power mode.

Claims17

Dependent claims

A semiconductor integrated circuit comprising:

a normal power supply line to which a power supply voltage is constantly supplied;
a virtual power supply line;
a first switch that connects said normal power supply line and said virtual power supply line in response to activation of a switch control signal;
a switch control circuit that maintains the activation of the switch control signal during a normal operation mode and inactivation of the switch control signal during a low power mode;
a first circuit block connected to said virtual power supply line at its power supply terminal;
a second circuit block connected to said normal power supply line at its power supply terminal;
and
a floating prevention circuit disposed between an output of said first circuit block and an input of said second circuit block, wherein
said floating prevention circuit has a second switch that connects a connecting node to a first voltage line in response to the inactivation of the switch control signal, and interrupts the connection between the connecting node and the first voltage line in response to the activation of the switch control signal, said connecting node being between the output of said first circuit block and the input of said second circuit block.

6 more elements

Dependencies are inferred from the claim text.