This part is a kind of semiconductor called A4988.

Function of this product has DMOS Microstepping Driver.

Manufacturers : Allegro

Image and pinout :

Some of the text within the PDF file :

A4988 DMOS Microstepping Driver with Translator and Overcurrent Protection Features and Benefits ▪ Low Rds(on) outputs ▪ Automatic current decay mode detection/selection ▪ Mixed and slow current decay modes ▪ Synchronous rectification for low power dissipation ▪ Internal UVLO ▪ Crossover-current protection ▪ 3.3 and 5 V compatible logic supply ▪ Thermal shutdown circuitry ▪ Short-to-ground protection ▪ Shorted load protection ▪ Five selectable step modes: full, 1/2, 1/4, 1/8, and 1/16 Package: 28-contact QFN with exposed thermal pad 5 mm × 5 mm × 0.90 mm (ET package) Not to scale Description The A4988 is a complete microstepping motor driver with built-in translator for easy operation. It is designed to operate bipolar stepper motors in full-, ha [ ... ]

A4988 PDF Datasheet Download