3.4 A 16MHz CMOS RC Frequency Reference with ±400ppm Inaccuracy from −45°C to 85°C After Digital Linear Temperature Compensation

In this work, we present a 16MHz RC-based frequency reference that achieves ±400ppm inaccuracy from -45°C to 85°C after a digital 2 -point trim. As shown in Fig. 3.4.1, it consists of a frequency-locked loop (FLL), which locks the frequency f _DCO of a digitally controlled oscillator (DCO) to the phase shift of a Wien-bridge (WB) RC filter [6]. The temperature dependence of the WB is compensated by information provided by a Wheatstone-bridge (WhB) temperature sensor [7]. The temperature dependencies of both bridges exhibit similar non -linearity, allowing high accuracy to be achieved with a 2-point trim.