This part is a kind of semiconductor called A3046LU.

Function of this product has HALL EFFECT GEAR-TOOTH SENSORS ZERO SPEED.

Manufacturers : Allegro MicroSystems

Image and pinout :

Some of the text within the PDF file :

3046, 3056, AND 3058 The A3046EU/LU, A3056EU/LU, and A3058EU/LU Hall effect gear-tooth sensors are monolithic integrated circuits that switch in response to differential magnetic fields created by ferrous targets. These devices are ideal for use in gear-tooth-based speed, position, and timing applications and operate down to zero rpm over a wide range of air gaps and temperatures. When combined with a backbiasing magnet and proper assembly techniques, devices can be configured to give 50% duty cycle or to switch on either leading, trailing, or both edges of a passing gear tooth or slot. HALL EFFECT GEAR-TOOTH SENSORS –ZERO SPEED Data Sheet 27612A† X X V CC 1 2 3 GROUND OUTPUT SUPPLY The six devices differ only in their magnetic switching values and operating temperature ra [ ... ]

A3046LU PDF Datasheet Download