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Compact linear current sensor aimed at space-constrained apps

26 Feb 2015

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Allegro MicroSystems has introduced the ACS718 current sensor IC that the company describes as an economical, high isolation solution for AC or DC current sensing in industrial, commercial and communications systems. The device boasts a small package that is suitable for space constrained applications, while its wide-body offer the creepage and clearance needed for high isolation.


The device consists of a low-offset, linear Hall sensor circuit with a copper conduction path located near the surface of the die. Applied current flowing through this copper conduction path generates a magnetic field that is sensed by the integrated Hall IC and converted into a proportional voltage. Device accuracy is optimised through the close proximity of the magnetic field to the Hall transducer. A proportional voltage is provided by the low-offset, chopper-stabilised BiCMOS Hall IC, which is programmed for accuracy after packaging.

The output of the device has a positive slope when an increasing current flows through the primary copper conduction path (from pins 1 through 4, to pins 5 through 8), which is the path used for current sensing. The internal resistance of this conductive path is 0.85mΩ typical, providing low power loss. Typical applications include motor control, load detection and management, switched-mode power supplies, and overcurrent fault protection.

Functional block diagram of ACS718

The terminals of the conductive path are electrically isolated from the sensor leads (pins 10 through 15). This allows the ACS718 current sensor IC to be used in high-side current sense applications without the use of high-side differential amplifiers or other costly isolation techniques.

The ACS718 is provided in a small, low profile surface mount SOICW16 package (suffix MA). The device is lead (Pb) free with 100 per cent matte tin lead frame plating. The device is fully calibrated prior to shipment from the factory.

The sensor IC supports 5V single supply operation, and offers factory-trimmed sensitivity and quiescent output voltage for improved accuracy.


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