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Current sensor achieves high accuracy by utilizing the AMR effect

June 19, 2012 | Christoph Hammerschmidt | 222902318
Current sensor achieves high accuracy by utilizing the AMR effect For precise current measurement in electric vehicles, battery management and in solar and wind inverters, chipmaker Elmos AG has developed its E524.5 sensor. The device features galvanic separation from the primary circuit, high dynamic range, and a customer configurable overcurrent detection.

Installation tolerances in the application can be compensated for by means of zero and sensitivity calibration which transforms into a high system accuracy. The sensor system embraces the sensor cell, the signal processing unit and two permanent magnets which generate a magnetic auxiliary field for the sensor element.

The E524.5 utilizes the Anisotropic Magneto-Resistive (AMR) effect. It measures the magnetic field generated by the primary conductor with the sensitive axis being located at the level of the sensing element. The size of the AMR effect makes the use of a flux concentrator redundant. The fast amplifier circuits in the closed loop circuit enable a high bandwidth of more than 500kHz. This in turn enables detection of the real value of pulse edges. The typical deviation is 1.5% FS across the entire temperature range from -40°C through +125°C. This is significantly better than the accuracy of Hall effect sensors (typ. about 5% FS).

A product-specific lead frame along with a sophisticated packaging technology makes it possible to implement the sensor as a system-in-package solution. All system components for primary current value acquisition are integrated in a JEDEC compatible SOIC16 package by means of an industry standard molding process. Additional pick-and-place processes as well as soldering steps are not necessary.

The difference in the magnetic field is generated by placing the primary conductor beneath the sensor package forming the shape of a U. By varying the primary conductor geometry the required differential field at the sensor can be adjusted according to the specific requirements of the application. Thus, only one current sensor is required for a wide range of primary currents.

For more information visit www.elmos.com










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