This brief presents a 0.9-mu W duty-cycle-modulated temperature sensor with a sub-mu A peak current for energy harvester-or micro-battery-powered systems. A compact sensing frontend is proposed to achieve low power, together with various device-level leakage and nonlinearity compensation techniques adopted to minimize the sensor error. In addition, a current-starved multivibrator which provides inherent clamping voltages is used for duty cycle modulation for overall energy savings. The sensor designed in 0.18-mu m CMOS process achieves a resolution figure of merit of 10.6 pJ.K-2, which is among the most energy-efficient designs to date. Trimmed at 30 degrees C, the sensor achieves +/- 0.85 degrees C precision from -30 degrees C to 120 degrees C. The maximum supply sensitivity is 0.7 degrees C/V for a 1.6-2 V supply.