Other Parts Discussed in Thread: LM5149-LM25149DESIGN-CALC
Hi support team
I want constant output 3.3V through connect FB to VDDA. but I don't know loop circuit how to control in this situation?
This thread has been locked.
If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.
You can use the LM5149-LM25149Design-Calc Quickstart tool to predict the loop response crossover frequency and phase margin when using internal feedback divider. WEBENCH model of LM25149-Q1 will also predict loop response.
When using internal feedback resistors, the output voltage VOUT pin is shared with the current sense amplifier. You can not inject a signal to measure loop response, it will disturb the peak-current control.
I recommend using time-domain step response if you need to test.
Hope this helps,
You need to use an external feedback divider in order to correctly inject the oscillator signal for bode plot measurement.
As Orlando recommended, you can take a look at a load transient with the fixed 3.3V setting and check that it is well damped with no ringing during the settling time. The quickstart tool is also helpful from this standpoint.