LM5175: FETs are getting hot and make a strange noise

Sven Meili

Part Number: LM5175

I have a problem with the LM5175. The output FETs are getting hot in idle mode and the inductor make a strange noise. I used the calculation tool for the part values. Is this maybe a problem with the layout?

Input: 9 - 40V, Output 24V, max. 8A.

Layout:

Schematic:

over 4 years ago

0 EM over 4 years ago

TI__Genius 11215 points

Hello Sven,

Thanks for using our part.

With respect to the inductor sound, it could be that it is vibrating due to its physical structure (this might happen in DCM) or it could be due to instability.

With respect to the layout, I would suggest you to check this page (and the following ones) to see some useful tips: https://e2e.ti.com/blogs_/b/powerhouse/archive/2017/02/20/four-switch-buck-boost-layout-tip-no-1-identifying-the-critical-parts-for-layout

The EVM is as well a good example of well-done layout https://www.ti.com/lit/ug/snvu440a/snvu440a.pdf?ts=1611594947210&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLM5175

The overheating could be due to the layout, a good layout should help to keep the FETs cool.

Could you please provide the measurements of input voltage, output voltage and switch nodes voltage?

Kind regards,

Elisabetta

0 EM over 4 years ago

TI__Genius 11215 points

Hello,

I haven’t heard back from you, so I’m assuming you were able to resolve your issue. If not, just post a reply below (or create a new thread if the thread has been locked due to time-out).

Thanks,

Elisabetta

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LM5175: FETs are getting hot and make a strange noise