A semiconductor integrated circuit includes one or more voltage drop detection circuits located at one or more measurement points within the integrated circuit to detect drops in the power supply potential at those points. The voltage drop detection circuits output signals indicating whether the power supply potential is within tolerance, or whether the power supply potential has fallen and corrective action is required. Being located near the measurement points, the voltage drop detection circuits can measure the power supply potential without being disturbed by electrical noise elsewhere in the semiconductor integrated circuit. The signals output by the voltage detection circuits can be reliably brought to external terminals despite the presence of such noise, because the output signals are bi-level signals.