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Wide-Band, Self-Calibrating, CMOS-Integrated HALL Magnetometer for Current Sensing Applications

Periodic Report Summary - IHACS (Wide-band, self-calibrating, CMOS-integrated HALL magnetometer for current sensing applications)

Electronic systems for smart power control are being increasingly installed in modern electrically-propelled vehicles, motors, and actuators for precise: a) position and motion adjustment, b) force and torque regulation, c) power efficiency optimization, and d) energy saving. The functionality of such controllers relies primarily on electric current sensors capable of monitoring precisely pulsed currents varying from DC up to frequencies as high as 100kHz and of reading current alteration rates as high as 10GA/sec. Additionally, modern power control applications require current sensing in multiple conductors positioned densely among each other. The aforementioned restriction poses limitations concerning sensor dimensions and cost as well as positioning distance between sensor and current conductors. Temperature stability is another important parameter that severely affects the performance of current sensors, especially in the case of industrial applications, where they are subjected to large temperature variations.

The IHACS project aims at the development of a new family of very compact, galvanically isolated, open-loop, wide-band, self-calibrating current sensors. The sensors are based on sophisticated multi-axes CMOS HALL magnetometers with no ferromagnetic parts that employ a new technique for sensitivity stabilization against temperature effects. The scientific and technological objectives of the proposed project are summarized in the sequel:

1. The development of a multi-axes magnetometer for pulsed-current sensing applications to exhibit unique performance characteristics with regard to: a) the extended current measuring range that is specified at 5kA with 0.02% resolution, b) the ultra-wide bandwidth that ranges from DC up to at least 1MHz, and c) the current alteration rate that is specified at 10GA/sec.
2. To design the aforementioned magnetometer in such a way to enable mounting as close as 10mm to current carrying conductors, called hereafter bus-bars. The latter condition, combined with the requirements stated previously, imposes the following specifications: a) 100mT flux-density measuring range with 0.02% resolution and b) 200kT/sec flux-density alteration rate.
3. To completely integrate the aforementioned magnetometer in a standard 0.35µm CMOS process with chip dimensions smaller than 3 x 3 mm2, in order to achieve unique characteristics with regard to: a) dimensions, b) spatial sensing resolution, c) performance-cost ratio, d) reproducibility, and e) production yield.
4. To develop a novel sophisticated temperature stabilization technique for HALL magnetometers that would allow for continuous-time calibration of magnetometer sensitivity assuring stability over the industrial temperature range extending from -25decC to +150degC.
5. To design, model, manufacture, and experimentally evaluate a series of flux-shaping devices to provide for proper magnetic field filtering and sensitivity boosting.

The contribution of IHACS partners is the combination of well-known physical principles and devices with sophisticated VLSI circuit design techniques, for the development of a new family of CMOS integrated current sensors with unique characteristics at competitive cost. IHACS consortium makes use of advanced modelling techniques, as well as special experimental equipment - much of which is tailor-made for the purposes of the project - to test, evaluate, and optimise the performance of the aforementioned systems.

Until now (month 24), IHACS consortium has delivered: a) The final version of the silicon integrated CMOS magnetometer that implements a patented, innovative, continuous calibration technique, b) The final version of the current sensor that employs magneto-dynamic effects for flux shaping and sensitivity boosting, and c) tailor-made measuring equipment for testing purposes. The aforementioned devices comply with IHACS objectives and specifications fulfilling, IHACS DoW up to date.