Thanks a lot! It works!
I use a small CD-ROM motor that has a spool with a rope.
I can compare with L6234.
2xBTS7960 gives some cogging, while L6234 works very smooth without any cogging.
But L6234 becomes very hot, unlike BTS7960 becomes barely warm.
I tried PWM frequence from 10 to 50000. No difference.
But may be my motor works beyond its means, and I need to try a little more powerfull motor.