Isolated magnetic current sensor provides fast response to over-current events

The MCS1805 from Monolithic Power Systems is a linear Hall-effect current sensor IC for ac or dc current sensing. The differential Hall array cancels out any stray magnetic field, making the sensor immune to magnetic interference. 

The MCS1805 is intended for use in functions such as load detection and management, and over-current fault protection. The sensor integrates fast over-current detection, which makes it simple to monitor the system for events such as short-circuits.

Galvanic isolation between the pins of the primary conductive path and the sensor leads allows the MCS1805 to replace opto-isolators or other isolation devices. The MCS1805 requires few external components. The device is supplied in an SOIC-8 package which has a footprint of 5 mm x 4 mm. 

The primary conductor’s low resistance allows large currents to flow close to the IC. This current generates a magnetic field, which is sensed at two different points by the integrated Hall transducers. The magnetic field difference between these two points is then converted to a voltage that is proportional to the applied current. A spinning current technique is used for a low, stable offset.