In microprocessors and DRAMs, on-chip temperature sensors are essential components, ensuring reliability by monitoring thermal gradients and hot spots. Such sensors must be as small as possible, since multiple sensors are required for dense thermal monitoring. However, conventional BJT-based temperature sensors are not compatible with the sub-1V supply of advanced processes. Subthreshold MOSFETs can operate from lower supplies, but at high temperatures their performance is limited by leakage [1,2]. Thermal diffusivity (TD) sensors achieve sub-1V operation and small area with moderate accuracy, but require milliwatts of power . Recently, resistor-based sensors based on RC WienBridge (WB) filters have realized high resolution and energy efficiency [4,5]. Fundamentally, they are robust to process and supply-voltage scaling. However, their readout circuitry has been based on continuous-time (CT) ΔΣ ADCs or frequency-locked loops (FLLs), which require precision analog circuits and occupy considerable area (>0.7mm2).