First surface-mount current sensor with reinforced isolation rating

25-02-2015 | Allegro | New Technologies

New from Allegro MicroSystems Europe are two new current sensor ICs, the first of their kind to offer economical high-isolation solutions for AC or DC current sensing in industrial, commercial and communications systems. The new ACS717 and ACS718 devices are offered in a small surface mount package that is ideal for space-constrained applications, although the width of the body provides the creepage and clearance distances needed to provide the high isolation. Each 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 which 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 optimum accuracy after packaging. The output of the device has a positive slope when an increasing current flows through the primary copper conduction path, which is the path used for current sensing. The internal resistance of this conductive path is typically 850 micro-ohms, providing a low power loss. The terminals of the conductive path are electrically isolated from the sensor leads, allowing the ACS717 and ACS718 current sensor ICs to be used in high-side current sense applications without the use of isolated operational amplifiers or other costly isolation techniques. Typical applications include motor control, load detection and management, switched-mode power supplies, and overcurrent fault protection. Both devices are offered in a small low-profile surface mount SOICW16 package (suffix MA). The devices are lead (Pb) free with 100% matt tin leadframe plating, and are fully calibrated prior to shipment, says the company.

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