LM5122EVM-1PH thermal performance at 12V and 48V output for 3A

Cage Chen

Prodigy 490 points

Other Parts Discussed in Thread: PMP7970, LM5122

Hi,

We are designing a 12V input to 48V for 3A output application.

Is there any thermal performance for this condition that can share with us?

Thanks a lot.

Best regards, Cage.

over 7 years ago

0 EricLee over 7 years ago

TI__Mastermind 46061 points

Hi

PMP7970 and PMP7965 are similar with your application. Please find the thermal data in the test report.

http://www.ti.com/tool/PMP7970
http://www.ti.com/tool/pmp7965

Regards,
EL

0 Cage Chen over 7 years ago in reply to EricLee

TI__Prodigy 490 points

Hi EL,

I have a question about the thermal result on page 5 of PMP7970.

It showed the 12V to 54V thermal result, and the temp of MOSFETs were about 6X degree C.

But the temp of inductor was about 100 degree C, why the temp of MOSFETs were far away below inductor?

Thanks a lot.

Best regards, Cage.

0 JohnTucker over 7 years ago in reply to Cage Chen

TI__Guru**** 191445 points

At 12 V input, the p-p inductor ripple current is 10.14 A. That is relatively a lot compared to the 2.5 A output current. Typically flat wire inductors do not perform well thermally with large ac ripple currents, even though the dc losses are small. That is most likely why the inductor is heating up so much. I will forward this to the circuit designer for his comment.

0 Cage Chen over 7 years ago in reply to JohnTucker

TI__Prodigy 490 points

Hi John,

Thanks a lot for your quick answer, and look forward to hearing from designer.

Best regards, Cage.

0 Xinyu Dai over 7 years ago in reply to Cage Chen

TI__Intellectual 925 points

Hi Cage,

Thank you for contacting us.

You are correct, the image on pg5 looks suspicious, at min Vin of 12Vin, the peak current is the highest and this will reflect on the low side switch FET. I built another same board, and re-run the thermal, the result makes sense, please see attached. This new image will be updated on TI.com within the next couple days.

Please let us know if there is anything we can help to design the LM5122 for you.

Best regards,

Max

0 Cage Chen over 7 years ago in reply to Xinyu Dai

TI__Prodigy 490 points

Hi Xinyu,

Thanks a lot for your help always.

Best regards, Cage.

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LM5122EVM-1PH thermal performance at 12V and 48V output for 3A