A Compact Resistor-Based CMOS Temperature Sensor With an Inaccuracy of 0.12 °C (3<inline-formula> <tex-math notation="LaTeX">$\sigma$ </tex-math> </inline-formula>) and a Resolution FoM of 0.43 pJ<inline-formula> <tex-math notation="LaTeX">$\cdot$ </tex-math> </inline-formula>K<inline-formula> <tex-math notation="LaTeX">$^{2}$ </tex-math> </inline-formula> in 65-nm CMOS

Abstract

This paper presents a compact resistor-based CMOS temperature sensor intended for dense thermal monitoring. It is based on an $RC$ poly-phase filter (PPF), whose temperature-dependent phase shift is read out by a frequency-locked loop (FLL). The PPF’s phase shift is determined by a zero-crossing (ZC) detector, allowing the rest of the FLL to be realized in an area-efficient manner. Implemented in a 65-nm CMOS technology, the sensor occupies only 7000 $\mu \text{m}~^{\mathrm{ 2}}$ . It can operate from supply voltages as low as 0.85 V and consumes 68 $\mu \text{W}$ . A sensor based on a PPF made from silicided p-poly resistors and metal–insulator–metal (MIM) capacitors achieves an inaccuracy of ±0.12 °C (3 $\sigma $ ) from −40 °Cto 85 °C and a resolution of 2.5 mK (rms) in a 1-ms conversion time. This corresponds to a resolution figure-of-merit (FoM) of 0.43 pJ $\cdot \text{K}~^{\mathrm{ 2}}$ .