Predrag Drljaca

Low-power 2-D fully integrated CMOS fluxgate magnetometer

In this paper, we present a low-power, two-axis fluxgate magnetometer. The planar sensor is integrated in a standard CMOS process, which provides metal layers for the coils and electronics for the signal extraction and processing. The ferromagnetic core is placed diagonally above the four excitation coils by a compatible photolithographic post process, performed on a whole wafer. The sensor works using the single-core principle, with a modulation technique to lower the noise and the offset at the output. In contrast to traditional fluxgate approaches, the sensor features a high degree of integration and minimal power consumption at 2.5 V of supply voltage that makes it suitable for portable applications. A novel digital feedback principle is integrated to linearize the sensor characteristics and to extend the linear working range.

Nonlinear effects in magnetic angular position sensor with integrated flux concentrator

We studied nonlinear behaviour of the angular position magnetic field sensor that consists of CMOS integrated circuit chip and a thin ferromagnetic disk. Developed numerical 3D model was compared with experimental results with a good agreement. Obtained numerical results were used to determine the linear magnetic working range of the sensor. We also calculated the nonlinear error for the disk positioning relative to the Hall elements and found 3.3% of error for the 10 /spl mu/m displacement. We proposed a simple amplitude calibration to strongly reduce nonlinearity coming from misalignment to 0.3% of the full scale. Additional nonlinearity from Hall elements has been discussed. The offset and sensitivity mismatch, contribute to the nonlinearity of the sensor less than 1/spl deg/.

Bridging the gap between AMR, GMR, and Hall magnetic sensors

By integrating a magnetic flux concentrator (IMC) at the surface of a Hall magnetic sensor, we can dramatically improve its characteristics. Here we compare the performance of a new IMC Hall sensor ASIC with the performance of traditional magnetic field sensors, such as AMR, GMR, and conventional Hall sensor ASICs. We find that the detectivities of AMRs and GMRs for AC magnetic fields are much better than those of Hall ASICs; for low-frequency fields, the performance gap is smaller; but for DC fields, the resolution of the IMC Hall ASIC is much better than that of GMRs and approaches the resolution of a nonswitched AMR. Also according other parameters, the IMC Hall ASIC is positioned in the gap between AMRs, GMRs, and the conventional Hall ASIC magnetic field sensors.

A Completely Scalable Lumped-Circuit Model for Horizontal and Vertical HALL Devices

A completely scalable lumped-circuit model for horizontal and vertical HALL devices is presented therein that can be efficiently implemented in SPICE-like EDA simulators. The model has been employed for the quantitative analysis of: a) geometrical, b) temperature, and c) field-dependent mobility effects, as well as for d) the dynamic response and e) the noise behavior of several HALL sensors. A series of experimental data is presented along with simulation results.

Low noise CMOS micro-fluxgate magnetometer

We present a new two-axis fluxgate magnetometer fully integrated in CMOS technology. The magnetometer exhibits excellent sensitivity of 2700 V/T and the magnetic equivalent noise spectral density of 6nT//spl radic/Hz at 1 Hz. The total power consumption is as low as 35 m W from the single 5 V power supply. The low noise characteristic is obtained using the combination of good magnetic . material properties and electronic post-modulation technique to reduce the noise coming from CMOS electronic part.

High Sensitivity Hall Magnetic Sensors Using Planar Micro and Macro Flux Concentrators

We have studied the sensitivity of Hall devices using planar magnetic flux concentrators of various lengths. By placing magneto-concentrators (MCs) on Hall device, we obtained sensitivity up to 100 V/T for a bias current of 1 mA and for a length of the MCs of 50 mm. This value is about 1000 times better then that of a conventional silicon Hall devices, without adding significant amount of noise. The magnetic gain is achieved using a combination of micro-integrated and macroscopic magnetic flux concentrators.

A 0.35um-CMOS, Wide-Band, Low-Noise HALL Magnetometer for Current Sensing Applications

A CMOS HALL magnetometer is presented herein that can be optimally used in current sensing applications thanks to its specific features. The magnetometer incorporates a set of integrated coils that generate a reference AC magnetic field to allow for sensitivity and offset stabilization against temperature variations.

Integrated Hall Microsystem with Current Re-Use

A new architecture of a Hall microsystem for low-power applications is presented. The innovation in this paper lies in the re-use of the electric current for biasing of several parts in the microsystem permitting substantial reduction of the current consumption. In this manner, four Hall devices were embedded into a differential difference amplifier, and signal treatment techniques for 1/f noise suppression were implemented to the system. The microsystem integrated in a standard 0.8 um double-poly, double-metal CMOS process exhibits an output sensitivity of 37.5 V/T and a magnetic field resolution of 500 nT/√Hz at 1 Hz. Its current consumption was reduced by 45% down to 2.4 mA compared to a similar Hall microsystem with conventional architecture having separated biasing of the sensing part and the electronic part.