All Hall-effect devices are activated by a magnetic field. The device must be mounted with a base and provided with an electrical connection. This includes that the loading current, environmental conditions, and supply voltage must be within the limits shown on the datasheet.
Magnetic fields have two important properties: magnetic flux density b (mainly referring to the strength of the magnetic field) and magnetic field polarity (magnetic north or magnetic south pole). For Hall-effect devices, the direction of the magnetic field in relation to their active region is also important. The effective area of a Hall-effect device (Hall element) is embedded on a silicon wafer that is parallel to and slightly close to a specific face of the package. This surface is also known as the marking surface because it is usually the side of the marking model (the datasheet for each device will show the effective area depth from the imprint surface). In order for the switch to work optimally, the magnetic flux lines must cross the active area (the imprint surface of a planar Hall element or the sensing edge of a perpendicular Hall element) vertically and must have the correct polarity when traversing. Because the active area is closer to the imprint surface on the back of the package and exposed to the imprint side of the wafer, this orientation produces a clearer signal.
In the absence of a magnetic field, most Hall-effect digital switches turn off (output open). These switches are only turned on if there is a magnetic field with sufficient magnetic flux density and the correct polarity in the correct direction. For example, the magnetic north pole will switch off when it is close to the imprint surface, while the magnetic north pole will have no effect. In an application, bringing the magnetic south pole of a small piece of permanent magnet close to the imprint surface of a planar Hall switch or the sensing edge of a perpendicular Hall switch (see Figure 8) causes the output transistor to turn on. When the magnet approaches from any direction, the output of the 3D Hall switch will turn on.