Hall effect rotational speed sensor integrated circuit
ALLEGRO MICROSYSTEMS

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

Magnetic field changes affect the two integrated Hall transducers and then are differentially amplified on the chip. Differential design provides immunity to radial vibration, within the device operating air gap range, by rejection of this common-mode signal change. Steady-state system offsets are eliminated using an on-chip differential bandpass filter with integrated capacitor. This filter also provides relative immunity to interference from electromagnetic sources. The device utilizes advanced temperature compensation for the high-pass filter, sensitivity, and Schmitt trigger switchpoints to guarantee optimal operation to low frequencies over a wide range of air gaps and temperatures.