Vertical Hall Research Articles

Open-Loop CMOS Current Transducer with Low Temperature Cross-Sensitivity

We present an open-loop CMOS current transducer without magnetic core consisting of a bus bar and a CMOS integrated magnetic sensor. The magnetic sensor is a combination of a circular vertical Hall device for low-frequency range and a pick-up coil for high-frequency range. The temperature cross-sensitivity of the Hall device is removed by measuring the angle of the magnetic field vector rather than its magnitude. The first measurement results show nonlinearity less than 1.5% over 0-150 A range, wide dynamic range 0-2.8 kA, high slew-rate 14 MA/s and low temperature cross-sensitivity 500ppm/°C over 100°C.

Dual-Range Electrical Current Sensor

We present a new type of contactless current sensor featuring two inherent ranges of low and high sensitivity. Thecurrent sensor consists of a CMOS integrated circuit with a thin ferromagnetic layer structured on its surface. TheCMOS circuit contains a combination of vertical (VH) and horizontal Hall (HH) elements and interface electronics. Theintegrated ferromagnetic layer (IMC) works as a magnetic flux concentrator in the low field range. In the high field rangethe IMC is saturated and the vertical Hall system gives a lower magnetic sensitivity. This approach allows extending thedynamic magnetic range to about 10'000.

Parallel-Field Silicon Hall Effect Microsensors With Minimal Design Complexity

A new class of Hall microsensors with minimal design complexity was suggested and experimentally tested. The devices consisting in n-Si substrate and three n+-strip contacts only are sensitive to a magnetic field parallel to the chip surface. Using a reference voltage generating with a specific bridge circuitry, the linear Hall voltage is extracted and the quadratic geometrical magnetoresistance is fully compensated. The internal noise of the design with a Hall contact located outside the sensor active region is at least ten times smaller than those of the three-contact element with an inside placed output electrode. This leads to enhanced resolution reaching Bmin ap 35 muT. A three-terminal multisensors generating simultaneously and independently strongly asymmetric voltage to the magnetic field direction and a Hall signal were devised too. The devices performance proved undoubtedly that new three-contact sensors could compete with the other well-known vertical Hall elements.

Miniaturized Circular Vertical Hall Device

A miniaturized circular vertical Hall device with 8 contacts was studied in terms of its sensitivity, biasing topologies and residual offset. The geometry accounts for about 30% lower sensitivity, but offers the possibility of biasing the whole device in all sampling phases, which proves better for residual offset.

Intrinsic limits of the sensitivity of CMOS integrated vertical Hall devices

Current researches on CMOS integrated Hall devices focus on the vertical Hall device (VHD) since this structure limits the performances of monolithic three-dimensional Hall probes. The well known conventional horizontal Hall device (HHD) has probably been brought closed to its optimal performances while integrated in CMOS technologies. On the contrary, the VHD which is more complex to study theoretically still asks for a better understanding in order to improve its performances that are lower than those of a HHD as it was demonstrated experimentally in many previous works. The aim of this paper is to discuss this experimentally observed difference between VHD and HHD through an analysis of 2D FEM calculations. Especially, we explain why the conventional VHD with two sensing contacts exhibits an intrinsic lower sensitivity. This lower sensitivity is responsible for the lower signal to noise ratio and the higher offset. We also introduce coefficients which allow to determine the sensitivity of a VHD depending on its geometry. Finally we explain why a measurement of the Hall voltage through four sensing contacts instead of two is mandatory to reach the maximum sensitivity.

First Vertical Hall Device in standard 0.35 μm CMOS technology

In order to lower the short-circuit effect due to the measurement contacts, Vertical Hall Devices (VHDs) are generally designed either in bulky N-type silicon or in the deep N-well of high-voltage CMOS technologies. In this last case, VHD can benefit from on chip circuitry for offset and 1/f noise reduction, but HVCMOS remains a costly technology. Using spinning-current, HVCMOS compatible VHDs with a resolution of 76 μT rms over a 1.6-kHz bandwidth have been demonstrated. The VHD presented here is designed in the shallow N-well of a low-cost 0.35 μm standard CMOS technology. Unlike conventional VHD, its measurement contacts are located outside the sensor active area. FEM simulations and experimental results show that the new geometry suppresses the short-circuit effect and strongly reduces the intrinsic offset and noise. Thus, without any noise and offset reduction method, this new small VHD (63 μm 2) reaches a resolution of 79 μT rms over a (5 Hz–1.6 kHz) bandwidth, and opens the way to the integration of 3D Hall sensors in low-cost standard CMOS technologies.

Modeling the meteoric dust effect on the equatorial electrojet

Dust particles of meteoric origin in the lower E-region can affect the conductivity parameters by varying the effective collision frequency and by causing electron bite outs through the capture of ambient electrons. In magnetized plasma, neutral dust particles can alter the effective collision frequency parameters and thus affect the Pedersen and Hall conductivities in the electrojet region. The Cowling conductivity profile is determined by the height profiles of the Hall and Pedersen conductivities. The collision parameters altered by the neutral dust particles can be considerably different from those estimated from atmospheric models, in the lower E-region heights where dust particles of meteoric origin are known to exist in large numbers. A significant fraction of these dust particles may capture free electrons from the ambient medium and get charged negatively. This can result in reduction in the number density of free electrons especially below the electrojet peak where the dust particles can be present in large numbers, at least on days of large meteor showers. This, in turn, can once again alter the vertical profile of the east–west Hall current driven by the vertical Hall polarization field and under favorable conditions, can even account for the reversal of the electrojet currents below the current peak. Assuming a realistic model for the distribution of neutral dust particles, the conductivity parameters are estimated here. Conditions under which the dust particles can cause partial reversals in the electrojet currents are critically examined here.

Three-Axis Teslameter With Integrated Hall Probe

The first commercially available teslameter with a fully integrated three-axis Hall probe is described. The Hall probe chip contains horizontal and vertical Hall elements, analog electronics, and a synchronization circuit. A horizontal Hall element measures the perpendicular component, and two vertical Hall devices measure the two in-plane components of a magnetic flux density vector. Current spinning in the Hall devices cancels offset, 1/f noise, and the planar Hall voltage. The analog electronic module of the teslameter cancels the residual offset and compensates temperature dependence and nonlinearity of the Hall voltages. The digital module provides analog-to-digital conversion and communication to a computer.

Multi-axis integrated Hall magnetic sensors

Conventional Hall magnetic sensors respond only to the magnetic field component perpendicular to the surface of the sensor die. Multi-axis sensing capability can be provided in the following two ways: (a) by integrating magnetic flux concentrators on the die, and (b) by using vertical Hall devices. Here we review the most important two-and three-axis integrated Hall magnetic sensors based on these concepts. Their applications include mapping of magnetic fields and sensing angular position.

On the height variation of the E-region cowling conductivity – effect of charged dust particles

Abstract. Height profiles of the Cowling conductivity in the electrojet region, estimated using the atmospheric parameters given by the existing models like CIRA or MSIS and measured electron density profiles, consistently show the heights of the electrojet current intensity peak to be more than 3 km below those estimated from in-situ measurements using magnetometers on board sounding rockets. Kulkarni and Muralikrishna (2005) attempted to explain this to be due to the effect of neutral dust particles. They reported that neutral dust particles, when they exist in sufficient numbers, can modify the collision parameters, especially in the lower E-region, where dust particles of meteoric origin are known to exist in large numbers, and thereby can modify the Cowling conductivity profile in the electrojet region. This work is extended here to include the effect of charged dust particles. Dust particles can become charged negatively by the attachment of ambient free electrons, and can thus reduce the number density of free electrons especially below the electrojet peak. This can alter the vertical profile of the east-west Hall current driven by the vertical Hall polarization field, thereby causing a net reduction in the electrojet current. Such a decrease in the electrojet current may be observed on the ground magnetograms. This mechanism, as proposed here, can operate only during periods of strong meteor shower activity, when the dust particle density at the assumed deposit height of 103 km can reach extreme values (for example, 5×104 cm−3 of 1-µm diameter dust particles). Such a dense dust layer may even cause a reversal in the normally upward vertical Hall polarization field, within the dust layer, causing a reversal of the electrojet currents below the current peak.

3상의 자계 검출을 위한 수직 Hall 센서의 제작

In this study, we have fabricated a three branches vertical Hall sensor for detecting three phases rotation informations of miniaturized brushless motor. The sensor gives three position signals phase shifted by , corresponding to the motor driving signals. The branch has one Hall output and one input each other. The central part acts as common driving input. Sensor has branch width of and distance from central electrode to Hall electrode of . The sensitivity of sensor is 250 V/ at magnetic field of 0.1 T. It has also showed three sine waves of Hall voltages with phase over a rotation. A packaged sensing part are and has been successfully tested on a motor rotation at a speed up to 60,000 rpm.

Interaction Between Magnetoresistor and Magnetotransistor in the Longitudinal and Folded Vertical Hall Devices

This study investigates the one-dimensional longitudinal and folded vertical Hall devices, fabricated in a standard 0.35-/spl mu/m CMOS process. The smallest nonlinearity error 0.18%, the minimum offset 0.29 mV, and the maximum supply-current-related sensitivity S/sub RI/=3.837 V/A/spl middot/T, are obtained with a 10-mA bias current excited by the supply voltage of 0.6 V. The main magnetic mechanism is that the filament current of the vertical magnetoresistor is directly injected into the base region of the bulk magnetotransistor (BMT) to increase the density of minority carriers and then enhance the magnetosensitivity. Furthermore, the induced Hall voltage of the longitudinal vertical Hall device is proportional to the bias current, but the folded vertical Hall device is inversely impacted. This advantage makes it possible to get a low-power folded vertical Hall device. The folded style not only reduces the nonlinearity error but also minimizes the offset. Unfortunately, the tradeoff is a fall in sensitivity. The BMT is applied to increase magnetic sensitivity and to compensate for this negative impact.

Contactless 360° absolute angular CMOS microsystem based on vertical Hall sensors

We have developed the first 360° contactless absolute angular microsystem using a CMOS two-dimensional vertical Hall sensor. The microsystem contains two groups of vertical Hall sensors, mutually oriented at 90°, and complete readout electronics. The spinning current method is used to extract the signals from the sensors. Projections onto two orthogonal axes of the external rotating magnetic field give the rotation angle sine and cosine functions, respectively. From these two output signals, the rotation angle is extracted using the four quadrant inverse tangent function without discontinuity or dead angle over 360°. An angular accuracy of less than ±0.5°(±0.14%) at room temperature with only the Hall sensors’ residual offset compensation is obtained. Using gain mismatch and phase compensation, an outstanding accuracy of ±0.17°(±0.05%) is achieved.

0.2 mT Residual offset of CMOS integrated vertical Hall sensors

Abstract A residual offset lower than 0.2 mT is obtained with a CMOS integrated vertical Hall (VH)-sensor microsystem. Instead of the conventional design with five contacts in the sensor active area, we apply a layout with only four contacts. This design shows a higher effectiveness for the offset reduction by the spinning current (SC) method, because of the symmetrical current flow for the two different biasing phases. Furthermore, to obtain very low offsets, coupled sensors are integrated with the spinning current electronics in the final microsystem. A sensitivity up to Sv=0.025 V/VT is achieved for these sensors without any additional technology step. The measured output noise level of the integrated microsystem (1.9 μT/ Hz ) is in the usual range of commercial integrated Hall-sensors. Our new developments open the way to the realization of compact, low-cost angular sensors with 10 bit resolution.

Theory of the vertical Hall effect in a dimensionally quantized system

The transverse redistribution of carriers that occurs in a 2D system under the effect of a tangential electric field and a magnetic field possessing a tangential component is studied. It is shown that the redistribution of carriers gives rise to a Hall voltage across isolated electrodes positioned above and under the quantum film. This voltage is determined by the 2D conductivity tensor and the transverse static electric polarizability of the 2D layer. The additional contribution that appears in the vertical Hall voltage because of the electron spin orientation induced by magnetic field and the spin-orbit interaction of electrons with the quantum well potential is determined.

A vertical Hall device in CMOS high-voltage technology

In this paper we demonstrate for the first time, how vertical Hall devices manufactured in CMOS technology attain sensitivities comparable to those of conventional silicon plate-shape devices without any additional etching step. This was achieved by taking advantage of the low doping levels of a high-voltage technology. An additional unconventional doping reduction method can further improve the sensitivity. The current related sensitivity of the presented devices varies from 18 V/AT up to 127 V/AT for different sensor geometry and doping concentrations. The linearity error is less than 0.04% for magnetic fields up to 2T.

Influence of silicon anisotropy on the sensitivity of Hall devices and on the accuracy of magnetic angular sensors

An orientation dependence has been measured for vertical Hall (VH)-sensors and for horizontal CMOS Hall plates fabricated on n-doped (1 0 0) silicon wafers. A sensitivity difference up to 15% at 6.5 T is measured for VH-sensors in the (0 1 0) plane in comparison with the one in the (0 1 1 ̄ ) plane. When non-conventional orientations are used in an angular sensor, an angular shift up to 4° is measured at 2 T. Planar Hall effect in CMOS devices can be minimized by a proper choice of the sensor orientation. A model is derived that relates these effects to the silicon material anisotropy. Design rules have been derived for the realization of highly linear and accurate silicon Hall magnetometers.

Lateral and Vertical Hall Microsystems

Lateral and Vertical Hall Microsystems

Planar Hall effect in the vertical Hall sensor

The planar Hall effect is theoretically and experimentally studied in the vertical Hall sensor (VHS). Compared to silicon plate-shaped devices where experimental and theoretical value correspond well, the experimental value for the vertical Hall device is about 10 times smaller than theory predicts. This fact is explained by anisotropy effects and by the unique self-compensating structure of the device. Thus, magnetic field transducers built with devices of this structure are particularly adapted to the measurement of magnetic fields with more than one component.

Not-plate-like Hall magnetic sensors and their applications

This paper is a survey of a new class of Hall devices which are not plate-like but have three-dimensional structures. The survey covers: the vertical Hall device, sensitive to a magnetic field parallel with the chip surface; the cylindrical Hall device, which behaves as a vertical Hall device combined with magnetic flux concentrators; the two-axis vertical Hall device, for the two in-chip-plane components of a magnetic field; and the three-axis Hall device, to measure all three components of a magnetic field. All these Hall magnetic sensors are fabricated using the “vertical Hall” silicon process and feature low supply current, low noise, and high long-term stability. Their applications include: high-accuracy magnetometry, long-range position sensing, angular position sensing, current sensing, magnetic scanning of documents, and more.