An Ultra-low power MCU SOC is described with integrated DC to DC power management and Adaptive Dynamic Voltage Control (ADVC) mechanism. The SOC includes the complete Synopsys ARC EM5D core MCU, featuring a full set of DSP instructions and minimizing energy consumption at a wide range of frequencies: 312K-80MHz. On-die Silicon sensors are utilized to continuously change the operating voltage to optimize power/performance for a given frequency and environmental conditions and also to resolve yield and life time problems while operating at low voltages. The core operates between 0.45-1.1V volts with a direct battery connection for an input voltage of 1.0-3.8V. The peak energy efficiency is 18μA/MHz. A comparison to state-of-the-art commercial SOCs is presented, showing a 3-5x improved current/DMIPS (Dhrystone Million Instructions per sec) compared to the next best chip.