I have been trying to predict the Phase margin for my design, Came across App note www.ti.com/.../slva381
The note describes to verify Phase margin of Regulator by counting the number of Bumps in the Step response.
So, I got Transient model of the part TPS54284 and simulated the step response. The step response looks like 
Now, This Step response don't have any Bumps and As per the App note the Phase Margin should be >50 degrees (1 bump or less).
But, When i got the average model and simulated, the Phase margin, I got is in 20s of degrees.
So,My question are
1. On the model itself, Is the result are due to discrepancy in the Transient and Average models of the part (i simulated using TINA TI) ?
2. What should be inferred, the whole process of verifying the bumps is not accurate,(difference in phase margin is in range of at least 30 degrees) ?
3. Could the Transient behavior (more intuitive) which looks free of any ringing be taken as final word, although the Average model predicts low (23 degrees)phase margin ?
