Part Number: LMR33630-Q1
Hi team,
LMR33630-Q1(400kHz version) is used by my customer in several projects.
They are all for 13.5V to 7.5V for automotive lighting application. The load are not the same, but all of them are <2A. The same SCHs are used, but with different layouts.
The test result of one of them is good, while the other two has similar issue.
You could see below waveforms of SW mode and inductor current of one issue board. The SW Freq is about 44kHz and work in DCM. The load current is about 900mA, which should make converter work in CCM. The peak current is about 2.26A.
Below is the Sch. The output cap seems too small, and may cause the stability problem. But this issue seems being caused by bad layout.
Here is the layout.
And I test the waveforms between AGND and PGND pin, It is as below.
And Zoom it in as below.
Do you think it is caused by bad layout?
If yes, please give some advise and help explain why this will make it work in DCM.
If no, please give some suggestions to move forward.
Thanks.
Robin