LM5118: LM5118MH Problem

Hi Sholmi,

I am currently on a biz trip and my colleague will take a look into this and answer you as soon as he can.

Thanks,

Youhao Xi, Applications Engineering

Hi Shlomi,

Thanks for reaching out with your questions.

Can you please send over the schematic?

Thanks,

Garrett

Hi Garrett,

The schematic attached on the first post.

I attach again.

Thanks,

Shlomi

7455.LM5118.docx

Shlomi,

Sorry about that, the first time I opened the document the schematic didn't load.

How many boards is this being seen on? On suggestion is to reduce the switching frequency to see if there is any improvement. Possibly down to 440kHz to see if there is any improvement.

Thanks,

Garrett

Hi Garrett,

Will check and advise.

Attached the schematic again so you can see it better.

Thanks,

Shlomi

V1040-PS24W-A.pdf

Hi Garrett,

I've already decreased the switching frequency to 450kHz.

The result was that the problem occurred at higher current.

The question asked was, why doesn't the converter switch to buck-boost mode as it should?

I've made the simulation with Webench, with the inductor I have, with the RT resistor I have and the load I use. The current sense resistor is the same.

I didn’t change the snubber and the capacitors since the schematic froze when I tried to change them. Even though, the values are close to those I have at my circuit, and according to my understanding, it shouldn't change the result.

According to the startup simulation, the converter should switch from buck to buck-boost, but in practice it doesn't.

Thanks,

Shlomi

Hi Shlomi,

Please contact me directly through email and we can discuss the customer's observations.

Thanks,

Garrett