MX1508 motor driver module
I also did not find any schematics, so here the results from reverse engineering: 


4 Channels like many H-Bridges
+/- is the high voltage source/input
IN1-4 are the input signals from your IC (pwm capable)
Motor A/B are the high voltage outputs (connect motor here)


Experiments: 


drives brushed motor in both directions (tested)
drives brushed motor at different speeds with pwm (tested)
does not drive BLDC properly using three phase pwm (choppy movement, jumping) 
direct replacement with an L298 makes smooth BLDC movement (code/wiring tested ok)


The pwm test is run on positive voltages only 0,0.5,1 instead of -1,0,1 as that's the usual setup.

Guess: 


the MX1508 is to slow at reversing
the MX1508 cannot "sink" at "0.5"


Resumee: 


usable for space saving brushed setups
not usable for BLDC