A 9.7-nTᵣₘₛ, 704-ms Magnetic Biosensor Front-End for Detecting Magneto-Relaxation
Xiahan Zhou, Enhan Mai, Michael Sveiven, Corentin Pochet, Haowei Jiang, Chih‐Cheng Huang, Drew A. Hall
Abstract
This article reports a low-noise magnetic sensor front-end with an 18-bit Zoom ADC for detecting temporal magnetic nanoparticle (MNP) relaxation. Techniques such as dynamic element matching (DEM) and magnetoresistive correlated double sampling (MRCDS) are proposed to remove the sensor and analog front-end (AFE) 1/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f}$ </tex-math></inline-formula> noise while a fast-settling Miller compensation (FSMC) technique is proposed to reduce the amplifier power. Collectively, these result in state-of-the-art input-referred noise performance (9.7 nT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> ) and a figure-of-merit (FoM) that is 6.6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> and 210 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> better than previously reported magnetic sensor and relaxation-based AFEs, respectively. A relaxation-based magnetic immunoassay (MIA) was performed to demonstrate the concept. This design is implemented in a 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS process and consumes 4.32 mW from a 1.8-V supply.