3.5 A 4mW 45pT/√Hz Magnetoimpedance-Based ΔΣ Magnetometer with Background Gain Calibration and Short-Time CDS Techniques

Low-noise, low-power digital-output magnetometers are essential for various applications, including security-gate systems, non-destructive inspections, and geomagnetic and biomagnetic measurement systems. To ensure accurate measurements, it is crucial to maintain the robustness of the conversion gain from the input magnetic field to the digital-output signal. This paper presents a $3.96 \mathrm{~mW} \Delta \Sigma$ magnetometer with an input-referred noise of $45 \mathrm{pT} / \sqrt{ } \mathrm{Hz}$. Gain robustness is realized via a proposed background gain calibration and low-power CDS techniques. An FoM for the proposed magnetometer is $1.25 \mathrm{fW} / \mathrm{Hz}$, setting a new benchmark for energy efficiency among state-of-the-art designs with digital output, while maintaining low noise characteristics.