A 310 nW Temperature Sensor Achieving 9.8 mK Resolution Using a DFLL-Based Readout Circuit
Aditi Jain, Haowei Jiang, Corentin Pochet, Drew A. Hall
Abstract
This brief reports a high-performance, low-power temperature sensor suitable for wireless IoT devices/RFID tags. The system utilizes a mostly digital approach to achieve energy-efficient, sub- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> operation with a resistor-based temperature sensor. A sampled, incomplete-settling, switched-capacitor-based Wheatstone bridge is read out using a digital frequency-locked loop (DFLL) while harnessing the quasi-periodic limit cycles to reduce in-band noise. Implemented in a 65 nm CMOS process, it consumes 310 nW and achieves 9.8 mK resolution in a 10 ms conversion time. This results in a 297 fJ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {\cdot }}\text{K}~^{2}$ </tex-math></inline-formula> figure-of-merit (FoM) and low energy (3.1 nJ/meas.).