This brief presents a 0.65% relative inaccuracy CMOS temperature sensor with a duty-cycle-modulated (DCM) output. It uses a BJT-based front-end to generate a proportional to absolute temperature voltage ( V _PTAT ) and a complementary to absolute temperature voltage ( V _CTAT ), which are then modulated to a digital-friendly duty-cycle output. Dynamic element matching with Kelvin connection (KC-DEM) is applied to improve the accuracy of V _PTAT . To enhance the robustness of the sensor, a continuous-time dynamic single-threshold hysteresis comparator with high energy efficiency is proposed. Implemented in a standard 0.13- μm CMOS process, the sensor has an active area of 0.086 mm ² and achieves an inaccuracy of ±0.54 °C ( 3σ) from -40 °C to 125 °C.