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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