High-current fully integrated current sensors in small footprint

November 02, 2016 //By Nick Flaherty
Allegro MicroSystems Europe has launched a family of fully integrated current sensor linear ICs in a new core-less package designed to sense AC and DC currents up to 100 A. 

The ACS780/ACS781 are provided in this new automotive-grade, low-profile (1.5 mm thick) sensor IC package that represents the highest current density of any Allegro current sensor IC package to date. 

This new package has a very small footprint and delivers extremely high power density for your 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-stabilized 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 8 to terminal 9), which is the path used for current sampling.

The internal resistance of this conductive path is typically 200 μΩ, 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 1 through 7 and 10), allowing the device to operate safely with voltages up to 100 V peak on the primary conductor.