This brief presents a versatile thermal sensor, which features explicit simplicity on both circuit and system level. High accuracy without the need for calibration is possible by using the NPN bipolar device. Not only the generation of PTAT and CTAT signals, but also the processing and basic A/D conversion is performed in the same feedback loop. This results in a robust and compact solution, that does not require any control signals. A prototype sensor occupies only 2475 µm2 silicon area in 16nm FinFET and consumes 30 µA at 0.95 V supply voltage. It achieves an accuracy of ± 1.56 ˚C (3σ) without calibration and a typical conversion speed of 40kS/sec., which are among best-in-class figures.