TPS549D22EVM-784: how to measure the loop?

Jerry Chen 

No.  D-CAP3 uses the VOSNS, PVIN and SW pins to generate an injection ramp internally and should not be used with external ramp injection.

For loop measurements, the loop injection point should be selects so that the injection impedance is between the output voltage and both VOSNS and FB.

See figure 6 in the attached blog - https://e2e.ti.com/blogs_/b/powerhouse/archive/2015/05/05/power-tips-how-to-measure-bode-plots-with-dcap-and-dcapx-regulators