Today's microprocessors and Systems-on-Chip are thermally limited. Many, therefore, employ dynamic thermal management (DTM) to maximize performance under a reliability constraint. Accurate thermal monitoring is critical as temperature underestimation can hurt reliability by excessively aging devices and overestimation can hurt performance by unnecessarily throttling computing components. Placing temperature sensors close to potential hotspots can help accuracy, but it is non-trivial as hotspots often form inside digital blocks consisting of densely placed digital cells. Large sensors can disrupt cell placement thereby increasing wire lengths and circuit delays. Furthermore, the sensor needs to operate from the same digital power grid as the circuit, one that can be scaled down to near-threshold regime via dynamic voltage scaling. Absent this ability, a separate power grid and dedicated supply voltage for the sensors further increases area overhead. In this paper, we present a sensor circuit that is compact and deeply voltage-scalable and can be embedded among digital cells with little disruption. Simulation results show that it achieves a comparable accuracy to other compact sensor circuits for DTM.