LM25145: lm25145 operating temperature rising

Emanuele Peruzzi

Part Number: LM25145
Other Parts Discussed in Thread: LM5146-Q1

Hello,

i'm working with lm25145, i have a board designed to regulate 12V output at 10A, starting from 24V input. The board is perfectly working. Testing this board on a load with 4A consumption, i see that IC and MOSFET temperature rise 27 °C more (from 20 °C to 47°C about). Can someone who has experience with these regulator tell me if that +27 °C rise, is normal or is too much? I am worried that if i put my board into a closed and unvented cabinet, temperature could easily arrive at 80 °C and the device could break soon.

Is there some documentation about failure rate over temperature for these regulators? Some MTBF tables, for example.

Can a +27 °C of temperature rise considered normal, for a power delivery to load, of about 48W??

Thank you.

Kind Regards

Emanuele Peruzzi

over 3 years ago

0 Timothy Hegarty over 3 years ago

TI__Mastermind 49597 points

Hi Emanuele,

The temperature rise doesn't sound excessive, but it shouldn't increase at light loads.

Please send the schematic and a completed quickstart calculator file for review. It's possible the selected MOSFETs are switching loss dominant, meaning a higher relative contribution to losses at light load. You can use 40V FETs for a 24 input. Also, take a look at the LM5146-Q1 EVM as this is 12V/8A/400kHz.

Regards,

Tim

0 Emanuele Peruzzi over 3 years ago in reply to Timothy Hegarty

Intellectual 510 points

ok, these schematic and calculator filled,

thank you.

0 Emanuele Peruzzi over 3 years ago in reply to Emanuele Peruzzi

Intellectual 510 points

LM25145calc.zip

and this is calculator sheet

0 Emanuele Peruzzi over 3 years ago in reply to Emanuele Peruzzi

Intellectual 510 points

Please have a look to the configuration files i sent, while i check your ev board files.

Another doubt: in document snvu591, paragraph 6.3 thermal performance, i see that temperature can rise to above 60 °C but i can t find any specification of how much is ambient temperature.

kind regards

Emanuele

0 Timothy Hegarty over 3 years ago in reply to Emanuele Peruzzi

TI__Mastermind 49597 points

enterHi Emanuele,

The ambient was room temperature (20-22degC). The quickstart file looks good, just make sure to use the derated ceramic output cap value for voltage (usually about 50%). I see you used 88uF now. Also, you can enter the compensation values on your schematic to check the loop.

Note that you can tie the IC's NC pins to the DAP (GMD) to improve the copper heatspreading effect from the IC.

Regards,

Tim

0 Emanuele Peruzzi over 3 years ago in reply to Timothy Hegarty

Intellectual 510 points

ok,

nice help, thank you!

Emanuele

0 Timothy Hegarty over 3 years ago in reply to Emanuele Peruzzi

TI__Mastermind 49597 points

Thanks, Emanuele.

Tim

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LM25145: lm25145 operating temperature rising