High-Accuracy, High-Isolation, Differential Current Sensor ICs
Allegro MicroSystems, LLC announces two new current sensor ICs that are economical and precise solutions for ac or dc current sensing. These devices are ideal for use in industrial, commercial, and communication systems that require very high voltage isolation. These devices are not for use in automotive applications. Both the ACS724KMA (5V) and the ACS725KMA (3.3V) are available in a very small package that is suited for space-constrained applications while saving cost due to reduced board area.
They are packaged in a high-isolation SOIC16 wide body surface mount package that provides reinforced isolation. The differential sensing technology provides immunity to interfering common mode magnetic fields from adjacent current traces or motors. Typical applications include motor control, load detection and management, switched-mode power supplies, and overcurrent fault protection.
Both devices consist of a precise, 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. The current is sensed differentially in order to reject common-mode fields, improving accuracy in magnetically noisy environments.
The inherent device accuracy is optimized through the close proximity of the magnetic field to the Hall transducer. A precise, proportional voltage is provided by the low-offset, chopper-stabilized BiCMOS Hall IC, which includes Allegro’s patented digital temperature compensation, resulting in extremely accurate performance over temperature. 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 0.85 mΩ typical, providing low power loss. The terminals of the conductive path are electrically isolated from the sensor leads (pins 9 through 16). This allows the ACS724KMA 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 ACS724KMA and ACS725KMA are priced at $2.24 in quantities of 1,000 and are provided in a low-profile surface-mount SOIC16 package. The leadframe is plated with 100% matte tin, which is compatible with standard lead (Pb) free printed circuit board assembly processes. Internally, the device is Pb-free. The devices are fully calibrated prior to shipment from the factory.
