From The Apple Wiki

Compass Sensor produced by AKM

AK8975/C is 3-axis electronic compass IC with high sensitive Hall sensor technology.

Small package of AK8975/C incorporates magnetic sensors for detecting terrestrial magnetism in the X-axis, Y-axis, and Z-axis, a sensor driving circuit, signal amplifier chain, and an arithmetic circuit for processing the signal from each sensor. Self test function is also incorporated. From its compact foot print and thin package feature, it is suitable for map heading up purpose in GPS-equipped cell phone or media tablet to realize pedestrian navigation function.


AKM Sensor [Archived 2016-03-22 at the Wayback Machine]