TPS53515RVER vs. TPS548A20RVER

Other Parts Discussed in Thread: TPS548A20, TPS53515


i have made two DC2DC designs in the Webench , i have try to simulate it to do a comparison between the two different designs yet the simulation always fails.

TPS53515RVER vs. TPS548A20RVER 

i don't get any clue why ... 

can someone assist with it?

Thank you very much