Design of noise detector circuits as compact as standard logic cells is proposed. High-density large-scale digital integrated circuits that embed such built-in noise detectors enable in-depth characterization of dynamic power supply and ground noises. Dependence of power supply and ground voltage drops on the location of active cell rows within 1.8-V standard cell-based digital circuits are consistently measured by 1.8- and 2.5-V built-in detectors fabricated in a 0.18-mu m CMOS triple-well technology. Measurements also show that ground noise distribution is distinctively more localized than power supply counterparts due to the presence of a substrate.