AC current sensor; differential output, galvanic isolation

August 29, 2014 // By Graham Prophet
ACS726 is a current sensor IC designed to provide an economical and precise solution for AC current sensing in industrial, commercial and communications applications; a built-in differential amplifier allows externally adjustable gain.

In addition to featuring galvanic isolation, its fully differential back-end amplifier can be used to adjust gain and bandwidth via external RC networks. The back-end amplifier is fully independent and, when unused, can be powered down to reduce power consumption. The fully differential output of this device gives better immunity to output offset drift as well as common-mode noise.

The low-profile device package makes it easy to incorporate into, for example, motor control, load detection and management, switched-mode power supplies, and overcurrent fault protection.

The device consists of a precise, low-offset, linear Hall sensor circuit with a copper conduction path located near the surface of the die. Device accuracy is optimised through the close proximity of the magnetic field to the Hall transducer. A precise, proportional voltage is provided by the low-offset, chopper-stabilised BiCMOS Hall IC, which is programmed for accuracy after packaging.

The output of the device has a positive differential voltage 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 1.1 mΩ typical, providing low power loss. The terminals of the conductive path are electrically isolated from the sensor IC signal leads, allowing the ACS726 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 ACS726 is provided in a low-profile surface mount QSOP24 package (suffix LF).

Allegro MicroSystems; www.allegromicro.com