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This paper introduces a real-time on-chip power and temperature sensor for active power management in scaled CMOS technologies. In a distinct departure from earlier power estimation techniques, this sensor measures the voltage drop due to a current load and converts it into pulse counts to get a power estimate in real time. Linear regression is used to estimate load current based on the measured output frequency at a given temperature. The same sensor is also used to estimate temperature in a mode where output time period decreases linearly with temperature. Measurement results show accuracy to within ±1.05°C for temperature estimation in the range of 22 °C-100°C and within ±10% of the actual power consumed (for loads ≤ 3.3 mA). Fabricated in 45-nm SOI technology, this power and temperature sensor occupies an area of 140 μm×140μm and has a power overhead of 120 μW at 1.2 V supply.