A1421

The A1421, A1422, and A1423 are ac-coupled Hall-effect sensors which include  monolithic integrated circuits that switch in response to changing differential  magnetic fi  elds created by rotating ring magnets, or when coupled with a magnet,  by ferrous targets. This family of devices also includes an integrated capacitor,  providing the high accuracy of analog sensing without an external fi  lter capaci- tor. This reduces cost and components, while improving the reliability of the fi  nal  sensor solution.

The magnetic fi  eld changes are sensed by two integrated Hall transducers and then  are differentially amplifi  ed on the chip. Differential sensing provides immunity to  radial vibration, within the device operating air gap range, by rejection of  common-mode signal changes. Steady-state system offsets are eliminated using an  on-chip differential bandpass fi  lter with integrated capacitor. This fi  lter also pro-
vides relative immunity to interference from electromagnetic sources. The device  utilizes advanced temperature compensation for the high-pass fi  lter, sensitivity,  and Schmitt trigger switchpoints to guarantee optimal operation to low frequen- cies over a wide range of air gaps and temperatures.