TPS54327 wenbench simulation question

The TPS54327 is duty cycle limited due to minimum off time constraints to maximum duty cycle of about 78.3%. So the absolute minimum input voltage for 3.3 V output is 4.21 V (or 4.5 V since that is the minimum operating input voltage). There are two other considerations.

When operating at maximum duty cycle, the load step transient performance is impaired. To maintain regulation during a load step, the duty cycle must increase rapidly to allow the output current to match the new load requirement. This is not possible if the duty cycle is already at the maximum.

Also, the 78.3% duty cycle limit is not a "hard limit". As the input voltage drops towards the minimum voltage, the line regulation degrades slightly at duty cycles between about 68% to 79%. For many users this is not an issue, but for safety margin, webench has a hard coded limit at 65%. Webench just displays a warning message for duty cycles above 65% but below the hard limit (webench may calculate a slightly different value than the approximate limit I used, D = 1 - Toff min * Fsw). 3.3 V output from 5 V input should be ok to use as long as you understand these two limitations.