Logic circuit and semiconductor integrated circuit device capable of operating by different power supplies

In a semiconductor integrated circuit device of the type wherein an input buffer circuit for inputting an external signal, an internal circuit for exhibiting a predetermined functional operation on the basis of the signal from said input buffer circuit and an output buffer circuit for outputting the output signal of said internal circuit to an external element are integrated on the same semiconductor substrate, the improvement wherein said output buffer circuit comprises:

• a selection signal generation circuit for generating a selection signal for selecting one of a plurality of power supply potentials;
• a power supply potential selection circuit for selecting one of said power supply potentials on the basis of said selection signal;
• a first semiconductor switch circuit for forming a first current path from said selected power supply potential to the output terminal to be connected to said external element in response to the output signal of at least one of said internal circuits;
• and
• a second semiconductor switch circuit for forming a second current path from said output terminal to a power supply potential, which is different from said selected power supply potential, in response to the output signal of at least one of said internal circuits;
• said second semiconductor switch circuit being not turned ON simultaneously with said first semiconductor switch circuit under the steady state.

In a semiconductor integrated circuit device system including:

• a first semiconductor integrated circuit device including an input buffer circuit for inputting external signals, an internal circuit for conducting a predetermined functional operation on the basis of the signal from said input buffer circuit and an output buffer circuit for providing the output signal of said internal circuit to an external element, that are integrated on the same semiconductor substrate;
• and
• a second semiconductor integrated circuit device including an input circuit for inputting the signal from said output buffer circuit of said first semiconductor integrated circuit device, an internal circuit for conducting a predetermined functional operation on the basis of the signal from said input buffer circuit and an output buffer circuit for providing the output signal of said internal circuit to an external element that are integrated on the same semiconductor substrate;
• the improvement wherein said output buffer circuit of said first semiconductor integrated circuit device comprises:
• a selection signal generation circuit generating a selection signal for selecting one of a plurality of power supply potentials including the power supply potential corresponding to the operation power supply potential difference of said input buffer circuit of said second semiconductor integrated circuit device;
• a power supply potential selection circuit for selecting the operation power supply potential of said input buffer circuit of said second semiconductor integrated circuit device on the basis of said selection signal;
• a first semiconductor switch circuit for forming a first current path from said selected power supply potential to the output terminal connected to said input buffer circuit of said second semiconductor integrated circuit device in response to the output signal of at least one of said internal circuits;
• and
• a second semiconductor switch circuit for forming a second current path from said output terminal to a power supply potential, which is different from said selected power supply potential;
• said second semiconductor switch circuit being not turned ON simultaneously with said first semiconductor switch circuit under the steady state.