A 0.97 nJ/Conversion BJT-Based Temperature Sensor With a Low-Power Two-Stage Dynamic Comparator

This article presents a low-power fully CMOS temperature sensor in a 65 nm process, suitable for monitoring the battery-powered application-specific integrated circuit (ASIC) designs. The circuit converts a proportional-to-absolute-temperature (PTAT) current to a complementary-to-absolute-temperature (CTAT) binary code using a low-power time-to-digital converter to-digital converter (TDC). To enhance conversion efficiency, we introduce a two-stage dynamic comparator that consumes 40% less power than conventional designs by enabling the preamplifier only when precise detection of the integration stop time is required. The 0.16mm²prototype consumes only 0.97 nJ/conversion, achieving a resolution figure of merit (FoM) of 0.018 nJ·K²$. Measurements show an inaccuracy of$± 0.85~∘$C ($3σ $) over a temperature range of –$20~∘$C to$+ 120~∘$C.