Three-Dimensional CMOS Differential Folded Hall Sensor With Bandgap Reference and Readout Circuit

This paper presents a 3-D differential folded Hall sensor (HS) fabricated using standard 0.18-μm CMOS technology; this HS includes 1-D folded lateral Hall sensor (FLHS) and 2-D folded vertical Hall sensor (FVHS). The proposed 3-D HS is laterally folded to reduce the effective conduction length and to decrease the offset voltage; a p
⁺
guard ring is used to narrow the conducting channel and to improve magnetosensitivity. The magnetosensitivity is improved two-fold and the offset is eliminated using the differential topology. The proposed 1-D FLHS is sensitive to magnetic induction perpendicular to the chip plane B
_Z
through the fast accumulation-slow release mechanism; the proposed 2-D FVHS is responsive to magnetic induction parallel to the chip plane, B
_X
and B
_Y
, based on the interaction between the magnetoresistor (MR) and magnetotransistor, where MR is more dominant. Notably, the proposed 3-D HS operates with a small offset voltage of 0.26 mV and without magnetic hysteresis. For 2-D FVHS, at a voltage gain of 89.6 dB, the maximum sensor output ΔV
_H
is approximately 196.4 mV at the applied magnetic induction of 5 mT and the maximum supply-current-related sensitivity S
_RI
is approximately 5943 V/A·T at a current consumption of 6.25 mA for x- or y-channel. For 1-D FLHS, the maximum ΔV
_H
is approximately 470.8 mV at 5 mT and the maximum S
_RI
is approximately 14790 V/A·T at a bias current of 6.25 mA for z-channel. The magnetosensitivity S
_RI
of 1-D FLHS is approximately 2.35 times that of 2-D FVHS. The designed 1-D FLHS is a comparable to the performance of other publications. However, it experiences a high nonlinearity error in output Hall voltage at a low bias current. By contrast, the proposed 1-D FLHS has a linear performance in output Hall voltage at a high bias current.