Patent ID: 7649373

Claim:
A semiconductor integrated circuit comprising: at least one functional block having a voltage drop detection circuit for detection a power supply voltage drop within the functional block and outputting a signal indicating whether or not the voltage drop is present, the voltage drop detection circuit being disposed within the functional block, wherein the voltage drop detection circuit compares the power supply voltage at a measurement point within the functional block with a reference voltage, and the voltage drop detection circuit includes an operational amplifier; and wherein the operational amplifier includes a first p-channel metal-oxide-semiconductor (PMOS) transistor having a source, a gate, and a drain, the source receiving the power supply voltage; a second PMOS transistor having a source, a gate, and a drain, the source receiving the power supply voltage; a first n-channel metal-oxide-semiconductor (NMOS) transistor having a source, a gate receiving the reference voltage, and a drain connected to the drain of the first PMOS transistor; a second NMOS transistor having a source, a gate receiving the power supply voltage to be measured, and a drain connected to the gates of the first and second PMOS transistors and the drain of the second PMOS transistor; and a third NMOS transistor having a source connected to ground, a gate receiving a gain adjustment signal, and a drain connected to the sources of the first and second NMOS transistors; the signal indicating whether or not the voltage drop is present being output from the drains of the first PMOS transistor and the first NMOS transistor.