A CMOS Front-End Hall Sensor Microsystem for Linear Magnetic Field Measurement With Best Tradeoff Between Sensitivity and SNR

Abstract

A monolithic integrated front-end CMOS Hall sensor microsystem working at the current mode is presented for linear magnetic field measurement. The geometry of the cross-shaped Hall plates is optimized to enable the best tradeoff between current sensitivity and signal-to-noise ratio (SNR) by theoretical modeling. Furthermore, a novel current-mode four-phase spinning current method combined with the correlated double sampling demodulation technique is proposed to amplify the weak Hall current signals and to cancel the high offset and noise. Fabricated using a standard 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> low-voltage CMOS technology, it is experimentally demonstrated that a maximum current sensitivity of 6.86%/T and an optimal SNR are achieved when the cross length-to-width ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L/W)$ </tex-math></inline-formula> ratio of the Hall plate is about 0.4. At a supply voltage of 3.3 V, the linearity of the Hall sensor microsystem is up to 99.9% in the magnetic field range within ±200 mT. The magnetic field resolution is as low as 100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{T}$ </tex-math></inline-formula> , the residual offset is less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$52~\mu \text{T}$ </tex-math></inline-formula> , and the power consumption is about 15.4 mW.