The AH1815 is an integrated Hall-Effect non-latched sensor. That’s nice but what does it do? Holding a magnet near the sensor will cause the output pin to toggle. This makes for a robust presence sensor. A reed sensor also works nicely, but can be limited by the glass encapsulation and size. A Hall-Effect sensor is much smaller, but can handle less current than a reed switch.
The AH1815 is a low-sensitivity, micro-power Omnipolar Hall effect switch IC, designed for portable and battery powered consumer equipment for home appliance and industrial applications such as smart-meter magnetic-tamper detection. Based on two sensitive Hall effect plates and a chopper-stabilized architecture, the AH1815 provides a reliable solution over the whole operating range. To support portable and battery powered equipment, the design has been optimized to operate over the supply range of 2.5V to 5.5V and consumes only 24µW with a supply of 3V.
The single open drain output can switch on with either a north or south pole of sufficient strength. When the magnetic flux density (B) perpendicular to the package is larger than operating point (Bop) the output is switched on (pulled low). The output is turned off when B becomes lower than the releasing point (Brp). The output will remain off when there is no magnetic field.