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LM5146-Q1: Maximum current

Part Number: LM5146-Q1

Hello, 

I'm trying to use LM5146-Q1 and I saw its maximum current rating said to be 30A on TI product search. 

In my understanding, the max current spec must follow FET's current spec, but I was wondering why you put certain number on max current. 

Is there any reason?

Also I tried the calculation excel file, and the power loss analyzer graph shows a weird behavior when load current exceeds 20A.

Is that normal?

  

Thank you in advance!

  • Hi JH,

    Practically, 20-30A is the limitations of the FET power losses, usually RDSON and respective I^2*R losses.

    It looks like your high-side FET is seeing significant power loss after 20A. You can try a lower RDSON FET but at some point this issue will still occur.

    You really dont want more than 1 or 2W of losses on each FET, unless you have heatsinking or cooling.

    Most Si FETs have RthetaJA of 40-50 C/W, so for every watt of power dissipation you'll see 40C temperature rise.

    Hope this helps,

    -Orlando

  • Thank you Orlando for your detailed answer! It helped a lot.