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In this paper we present a completely on-chip voltage regulation technique which promises to adjust the degree of voltage regulation in a digital logic chip in the face of process induced delay variations so as to minimize energy dissipation while always guaranteeing the target operating frequency. For this purpose the delay of a critical path replica of the circuit being regulated is constantly compared with the target delay to provide the regulator with the information needed to select the optimum voltage levels. The proposed solution is even move attractive in that no external components are required. Based on this scheme, a completely on-chip voltage regulator has been fabricated in a commercial 0.5 μm CMOS process and used to generate the inner rail voltages for a DSP multiplier-accumulator (MAC) implemented in mixed swing QuadRail. Measured results indicate that the voltages generated by the regulator offer a very high degree of load regulation thus verifying the fast response time of the on-chip output buffer.