A CMOS Resistor-Based Temperature Sensor with a 10fJ·K2 Resolution FoM and 0.4°C (30) Inaccuracy from -55°C to 125°C after a 1-point Trim

Abstract

Energy efficiency and accuracy are important specifications of CMOS temperature sensors. BJT -based sensors achieve state-of-the-art accuracy [1], while Wheatstone-bridge (WhB) sensors achieve lower accuracy but state-of-the-art energy efficiency [2], [3]. This paper presents a WhB sensor that is read out by an energy-efficient continuous-time delta-sigma modulator (CTDSM). Compared to [2], [3], the modulator achieves better energy efficiency with the help of a return-to-CM (RCM) DAC and an OTA with a tail-resistor linearization scheme. Moreover, better accuracy is achieved by embedding the DAC in the bridge and by using more sensitive silicided-diffusion resistors instead of silicided-poly resistors. Compared to the state-of-the-art [3], the proposed sensor achieves a 2× improvement in resolution FoM (10fJ.K2), and a 2× improvement in inaccuracy (0.4° C(3σ) from -55° C to 125°C after a 1-point trim).