P5.3 - Architecture of an Integrated AMR Current Sensor (IACS) System for a Wide Range of Automotive Applications

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
P5 - Magnetic
W. Schreiber-Prillwitz, A. Nebeling - Elmos Semiconductor AG, Dortmund (Germany), G. von Manteuffel, C. Nau - Sensitec GmbH, Lahnau (Germany)
774 - 779


A new anisotropic-magneto-resistive-effect (AMR) based current sensor system is presented, with special emphasis on features and design aspects to e considered using this 'system-in-a-package' approach.
Besides Hall-sensors, AMR-based sensors are increasingly entering the field of angular and linear position as well as current measurement. The described current sensor is designed for high resolution and fast electronic measurement of DC, AC or pulsed currents. The sensor exhibits no hysteresis as is present in iron core based solutions. The reason lies in the high sensitivity of the AMR sensors that makes an additional iron core needless. The system works in closed loop operation, which enables high linearity and avoids temperature effects. In contrary to Hall-effect based sensors, the described system enables a differential magnetic field measurement by an advanced geometry of the magneto-resistive elements. With this, the sensor is immune to homogeneous interference field.
The complete system includes the AMR sensor with the compensation conductor for the closed loop principle integrated on the same substrate, a highprecision signal conditioner IC, and two biasing magnets. All components are mounted on one functional leadframe, which will be assembled by standard methods, and overmolded by a standard molding process into a JEDEC compliant SO16 package which can easily be assembled in SMT to the PCB. The current to be measured is fed trough an U-shaped conductor line on the PCB, usually below the sensor device. With this the sensor is decoupled galvanically from the system.
The system accuracy can be improved by using either the internal or an external reference voltage. This further reduces temperature drift, and several sensors can share the same reference voltage. The adjustable overcurrent detection enables fast response in overload situations to prevent damage to the power units.
The major advantages of this system are its high bandwidth and high dynamic range offered by the AMR measurement principle, combined with a negligible hysteresis and improved linearity features. The possibility of end-of-line calibration in the application environment at the production site allows for an optimum sensitivity adjustment and improved system accuracy.
The proof of feasibility of the architecture will be presented.