Part Number: TPS50601A-SP
I am performing a startup analysis on the Buck converter TPS50601A and have experienced strange behavior with regards to the relationship between the output and the input voltage. The Buck is powered by a 5Volt rail which is ramped up from 0 to 100 in .8ms. The 5Volt rail is directly connected to the EN pin through a 10k ohm resistor.
This issue I am having is the output voltage which is set to 3.73 volts is crossing over the rise of the 5 volt input during startup in simulation as shown below. Not only does this happen for 5 volts, but it behaves the exact same way when the input voltage is set to 2 volts.
Has anyone every experienced something such as this before? Is there a solution to this problem?
I have attached a photo of my circuit capture, as well as the simulation results. 
