This IC can be considered something in the middle of Allegro-Sanken line for unipolar stepper motors. Probably it is the easier to find on the market. It is really interesting because it's internal circuitry provide a current limiter after a short period of time (around 10 secs) of inactivity.

As usual: microstepping (up to 1/16), 3A of current/phase,  44V max. The circuitry is quite simple (and the pcb as been studied to be milled easily) and follows the traditional style of the maker:

In the schematics have been used two resistor of .5 ohm but any resistor between 0.2-2ohms will be fine remembering that the current for any phase of the motor is given by:

I=Vref/Rs (with Vref >.1V and <2V). The reset has been disabled, useless in a normal use, and the enable pin managed by a small mosfet.

The dip-switch can be replaced by small bridges. here follows the table of steppings:

M1 M2 (pins of the IC)

H   H   half step
H   L   quarter step
L   H   eight step
L   L   sixteenth step