This is a breakout board for ON Semiconductor’s AMIS-30543 microstepping bipolar stepper motor driver, which features SPI-adjustable current limiting, 11 step modes (from full-step through 1/128-step), back-EMF feedback that can be used for stall detection or optional closed-loop control, and over-current and over-temperature protection. The board operates from 6 V to 30 V and can deliver up to approximately 1.8 A per phase without a heat sink or forced air flow (it is rated for 3 A per coil with sufficient additional cooling).

More data: https://www.pololu.com/product/2970