9.1 A resistor-based temperature sensor with a 0.13pJ·K2 resolution FOM

Temperature sensors are often used for the temperature compensation of frequency references [1–5]. High resolution and energy efficiency are then critical requirements, the former to minimize jitter and the latter to minimize power dissipation in a given conversion time. A MEMS-resonator-based sensor meets both criteria [1], but requires two resonators. In principle, resistor-based sensors also meet these criteria, and are CMOS compatible, but previous designs have been limited by the power dissipation [2–4] or 1/f noise [6] of their readout electronics. This paper describes a CMOS temperature sensor that digitizes the temperature-dependent phase shift of an RC filter. It achieves 410µK
rms
resolution in a 5ms conversion time, while consuming only 160µW. This corresponds to a resolution FOM of 0.13pJ·K
²
, a 5× improvement on previous CMOS sensors [6].