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LM25118 max current

Andrew Lee1
Prodigy 20 points

Other Parts Discussed in Thread: LM25118

Hello All,

Datasheet for LM25118 indicates that max output current is 4A.

However WEBENCH allow setting up to 20A and will generate a circuit given current requirements above 4A.

May I know which is the correct current limit for LM25118 ?

Thanks.

  • 0
    TI__Intellectual 2155 points

    Hi Andrew,

    For a regulator with external FETs such as the LM25118, the max output current of the design depends on the peak switch current. The output current is limited by the current rating in the FETs chosen, so you can feasibly create a 20A design provided you have FETs that can handle the current.

  • 0 in reply to Kevin Ip
    Prodigy 20 points

    Hello Kevin,

    I noticed that in some variations of current & footprint/efficiency optimization, WEBENCH gives efficiency above 100% (e.g. LM25118 with Vin(min)=3, Vin(max)=12.5, Vout=5, Iout=6A give efficiency of 120% when current is 3.6A )

    Can the suggested component BOM & values be used or should I change the design inputs ?

    Thanks & Regards,

    Andrew

  • 0 in reply to Andrew Lee1
    TI__Intellectual 2155 points

    Hi Andrew,

    Good catch.  It looks like the power dissipation on the high side FET was miscalculated at those operating conditions and thus the efficiency was erroneous. 

    I tried changing the FET in the BOM list to an alternate FET and this seemed to correct the error.  You can also try using the different optimization settings to get a BOM you would like.  Can you post a BOM you intend to use?  I can review it if you would like.