LTspice: time step too small error
The solver probably doesn't like the open ports SDCOM and SD on U1. If they really are supposed to be open, put a 1e6Ω or 1e9Ω to ground (or whatever value they should be set to). This helps the solver find the value on those ports. 

They are probably high impedance to a gate of a mosfet or something like that, if so, its either a floating net or close to it, floating nets are hard to solve for, so you need a current and a voltage so the solver can solve the net.