PCB-mount current sensor rejects stray field effects

May 17, 2016 // By Graham Prophet
Allegro Microsystems' ACS724KMA is a high-accuracy, high-isolation, differential current, surface mount sensor IC, offering improved performance in a low profile, small footprint package for applications that require very high voltage isolation, and with measurement ranges up to ±65A.

The ACS724KMA is available in a high-isolation SOIC16 wide-body surface mount package that provides reinforced isolation allowing it to be connected directly to line voltage without needing additional isolators. The small package is suitable for space-constrained applications and also saves cost through reduced board area. All eight pins on one side of the package are dedicated to the primary (measured) current path; four pins in and out. The resistance of the primary current path is 0.65 mOhms for low loss and heating. The inherent device accuracy is optimized through the close proximity of the magnetic field to the Hall transducer. A precise, proportional (to measured current) voltage is provided by the low-offset, chopper-stabilized BiCMOS Hall IC.

The internal structure of the device uses differential sensing technology to provide immunity to interfering common-mode magnetic fields from adjacent current traces or motors. The terminals of the conductive path are electrically isolated from the sensor leads. This allows the ACS724KMA current sensor IC to be used in high-side current sense applications without the use of high-side differential amplifiers or other isolation techniques. Typical applications include motor control, load detection and management, switched-mode power supplies, and overcurrent fault protection.

Allegro has also previewed its ACS780xLR: a fully integrated linear current sensor IC in a new coreless package designed to sense AC and DC currents up to 150A. The automotive-grade, low-profile (1.5 mm thick) sensor IC package has a very small footprint of 6.4 × 6.4 mm.

The Hall sensor technology used in the ACS780xLR incorporates common-mode field rejection to optimise performance in the presence of interfering magnetic fields generated by nearby current-carrying conductors.