Digitally Self-Calibrated RC Oscillator Utilizing Farey Search Algorithm Under ASIL-D Conditions Within AEC-Q100 Grade 0 Temperature Range

High-safety automotive applications demand extensive trimming over a wide temperature range due to AEC-Q100 Grade 0 and ASIL-D requirements. To mitigate the trimming burden, this paper introduces a digitally self-calibrated RC oscillator (RCO) leveraging the Farey search algorithm (FSA) coupled with a fractional current-steering DAC (FIDAC) and a loop break (LB). The FIDAC generates denser trimming currents in a reduced area, while the FSA optimizes the FIDAC settings. The dynamic LB ensures the connection between the RCO and its reference during calibration phases, and isolation during normal operational states for cross-validation. The prototype RCO fabricated in 180nm CMOS process achieves 0.55% <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\sigma $</tex-math> </inline-formula>-inaccuracy (280 samples) for process variations and 0.56% <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\sigma $</tex-math> </inline-formula>-inaccuracy (56 samples) across −40°C to 150°C, meeting the AEC-Q100 Grade 0 temperature range requirement without manual trimming and fulfilling the ASIL-D isolation criteria.