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 0.16 $\text{mm}^{2}$ prototype consumes only 0.97 nJ/conversion, achieving a resolution figure of merit (FoM) of 0.018 nJ $\cdot $ $\text{K}^{2}$ . Measurements show an inaccuracy of $\pm 0.85~^{\circ }$ C ( $3\sigma $ ) over a temperature range of – $20~^{\circ }$ C to $+ 120~^{\circ }$ C.