Automotive Grade, Galvanically Isolated Current Sensor ICs
Allegro MicroSystems, LLC announces two new current sensor ICs that are economical and precise solutions for AC or DC current sensing in industrial, automotive, commercial, and communications systems. Allegro’s ACS724 (5 V) and ACS725 (3.3 V) are highly accurate devices with a very small package. Both devices are ideal for space constrained applications that will save overall costs due to reduced board area.
Typical applications include motor control in automotive power braking applications, oil and transmission pumps, or HEV charging circuits. The device is also well suited for load detection and management, switched-mode power supplies, and over-current fault protection in industrial, computer and consumer applications tied to line voltage.
These new 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 is programmed for accuracy after packaging. The output of the device has a positive slope when an increasing current flows through the primary copper conduction path (from pins 1 and 2, to pins 3 and 4), which is the path used for current sensing. The internal resistance of this conductive path is 1.2 mΩ typical, providing low power loss. The terminals of the conductive path are electrically isolated from the sensor leads (pins 5 through 8). This allows the ACS724 and ACS725 current sensor ICs to be used in high-side current sense applications without the use of high-side differential amplifiers or other costly isolation techniques.
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| Functional Block Diagram. |
Both devices are provided in a small, low profile surface mount SOIC8 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, except for flip-chip high temperature Pb-based solder balls, currently exempt from RoHS. The devices are fully calibrated prior to shipment from the factory.
