High-current density sensor provides precision programming

1st November 2016
Alice Matthews

A family of fully integrated current sensor linear ICs has been released by Allegro MicroSystems Europe which are in core-less packages designed to sense AC and DC currents up to 100A. Allegro’s ACS780/ACS781 are provided in this automotive-grade, low-profile (1.5mm thick) sensor IC package that represents the highest current density of any Allegro current sensor IC package to date.

This package has a small footprint and delivers high power density for current sensing applications. The Hall sensor technology also incorporates common-mode field rejection to optimise performance in the presence of interfering magnetic fields generated by nearby current-carrying conductors.

The devices consist of a precision, low-offset linear Hall circuit with a copper conduction path located near the die. Applied current flowing through this copper conduction path generates a magnetic field which the Hall IC converts into a proportional voltage. Device accuracy is optimised through the close proximity of the primary conductor to the Hall transducer and factory programming of the sensitivity and zero-ampere output voltage at the Allegro factory.

Chopper-stabilised signal path and digital temperature compensation technology also contribute to the stability of the devices across the operating temperature range. High-level immunity to current conductor dV/dt and stray electric fields is offered by Allegro proprietary integrated shield technology, for low-output voltage ripple and low-offset drift in high-side, high-voltage applications. The output of the device has a positive slope (>VCC/2) when an increasing current flows through the primary copper conduction path (from terminal eight to terminal nine), which is the path used for current sampling.

The internal resistance of this conductive path is typically 200μΩ, providing low power loss. The thickness of the copper conductor allows survival of the devices at high overcurrent conditions. The terminals of the conductive path are electrically isolated from the signal leads (pins one through seven and ten), allowing the device to operate safely with voltages up to 100V peak on the primary conductor.

These sensor ICs are suited for automotive, industrial and computer applications. Automotive applications include EPS and DC/DC converters and oil and HVAC pumps that require higher currents. Industrial applications include low side sensing in VFD and other motor control systems. Other applications include computer servers power supply output current sensing as well as telecom inverters.

The devices are fully calibrated prior to shipment from the factory. The ACS780xLR family is lead (Pb) free. All leads are plated with 100% matt tin and there is no Pb inside the package. The heavy gauge leadframe is made of oxygen-free copper.

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