During testing of LM25149-Q1, it was found that the voltage variation of the upper and lower tube drive stage may be abnormal and the waveform is as follows.
Iout=1.5A HO and SW waveforms will have large wave jitter.
Iout=4.5A, HO LO duty cycle unstable, HO/LO high for short duration
Iout=6.5A duty cycle starts to be stable
Voltage peaking at Iout=8.5A HO and SW fluctuates periodically
The peak voltage of Iout=9.5, HO and SW will appear as follows
May I ask:
1. What is the cause of HO jitter in light load mode, what load impact will be caused, and whether there is an optimized method or need to do so;
2. Is the duty cycle unstable at Iout=4.5A because it is still in PFM mode? What is the boundary between PFM mode transition to PWM mode?
3. Why does the HO&SW voltage peak cycle fluctuate at Iout=8.5A?
4. The HO LO waveform under heavy load (Iout> 9.5A) is very strange: It feels like the sine wave superimposed on it has reached a certain limit and caused the HO to re-enter another PFM mode? And the sine wave still affects the HO&SW voltage amplitude, please help analyze the cause of the anomaly.
Thanks!
