LAUNCHXL-F280049C: Single Time Graph Windows does not show small signal of SFRA

Andreas Jedek said:

Until 4.g everything is fine. 

Are you able to see the transient load response in step 4.g. as expected?

Andreas Jedek said:

 I see still have a step which is not there. The output current is constant. The output voltage is constant. 

from sample 300 i can see noise on the signal that I expect all the time from the beginning.

and when I start SFRA I see on the high level the sinus, but why is it up to 300sample low?

If you mean the gap from 0 to 2.2V, this is most likely an artifact of viewing the TCM buffer before the trigger condition is met.  I see that the TCM state is Armed, which would explain why the Lead and Capture Frames are still cleared to 0, while a circular buffer of temporary values is stored in the Monitor Frame.  The TCM is waiting for the TCM to be triggered.  Note the similarity to the blue waveform From the DCL User's Guide:

I recommend adjusting the TCM trigger Min and Max levels so that the TCM trigger condition can be met.  The instructions in TIDM-DC-DC-BUCK for setting the Min and Max levels to be triggered_V +/- 100mV should work most of the time for the transient load response.  A tighter range might be needed for capturing the SFRA injection.

thanks tlee!

from where did you get the Diagram?

-Andreas