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WEBENCH® Tools/LM5121-Q1: lm5121 max output current

huanhuan Liu
Prodigy 60 points
Part Number: LM5121-Q1
Other Parts Discussed in Thread: LM5122-Q1, LM5121, LM5122

Tool/software: WEBENCH® Design Tools

I don't find max output current or max power dissipation of lm5121-q1 in the datasheet, but when I use webench tool, I set the output current to 10A and it reports an error. When I change the output current to 1A without changing other input conditions, it successfully generates a circuit.

Then I change the chip to LM5122-Q1 and use 10A output, also successful.  

So I wonder what is the max output current or output power of LM5121-Q1 and LM5122-Q1, thanks!

LeoLiu

  • 0
    TI__Guru* 78400 points
    Hi Huanhuan,

    Thank you for your interests in the LM5121-Q1. Both LM5121 and LM5122 are controllers and the maximum current is not limited to a specific level. It is the results of MOSFETs, inductor, and current sense resitor that you select. Also note that the Webench references to a real circuit board which is mostly the evaluation board, and thermal issue can be an constrain for that board, and this also limits the components to be selected by Webench. A trick that often works is to set the ambient temperature to -40C and the Webench may be able to create your design. If this is the case, you need to pay attention to your final board thermal performance, and optimize your layout and add necessary heatsink.

    Thanks,
    Youhao Xi, Applications Engineering.
  • 0 in reply to Youhao Xi
    Prodigy 60 points
    For LM5121 or LM5121-Q1, the max ambient temperature range is 0-125℃，and setting to 0 ℃ can't create a design working at 10A.
    Maybe I will just use LM5122-Q1 instead.
  • 0 in reply to huanhuan Liu
    TI__Guru* 78400 points
    Hi Huanhuan,

    Just check if you still have the issue. Like I mentioned earlier, you can use the webench design as the start point and fine tune on your real circuit. The power circuit selection can be updated to meet your performance requirement. Just note that both LM5121 and Lm5122 will support operation up to Tj=150C, but the EC table parameters are guaranteed up to Tj=125C. For your 125C ambient, the Tj will be higher so the EC table limits may become wider.

    Thanks,
    Youhao