This part is a kind of semiconductor called A1421.

Function of this product has High Precision Hall Effect AC-Coupled Differential Sensor IC.

Manufacturers : Allegro MicroSystems

Image and pinout :

Some of the text within the PDF file :

A1421, A1422, and A1423 High Precision Hall Effect AC-Coupled Differential Sensor IC with Integrated Filter Capacitor Features and Benefits • Integrated tracking capacitor • Used for sensing motion of ring magnet or ferrous targets • Wide operating temperature range • Operation with magnetic input signal frequency from 20 Hz to 30 kHz • EMI/ESD-resistant • Large effective air gaps • 4.0 to 26.5 V supply operating range • Output compatible with CMOS logic families • Reverse battery protection • Resistant to mechanical and thermal stress • Accurate true zero crossing switchpoint (A1421 only) • High vibration immunity, in running mode (A1423 only) Package: 4 pin SIP (suffix K) Description The A1421, A1422, and A1423 are AC-coupled Hall-effect sensor ICs which include [ ... ]

A1421 PDF Datasheet Download