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LM25118 efficiency at 3-22Vin and 24V 0.01A Vout...

Amanda Ross95
Intellectual 2740 points
Other Parts Discussed in Thread: LM25118, LM5000, LM5002, TPS55340

Good Morning,

I am attempting to help a customer find a good solution for a 3-22V input and 24V @ 0.01A output. Webench gave me a solution using the LM25118 but it doesn't provide an efficiency. Is this because the effieciency is so low and if so could you give me an idea of what that value would be? I've attached the document from Webench if that helps. 

Thank you so much for your time!

-Amandawebench_design_4461414_59_777761928.pdf

  • 0
    TI__Prodigy 200 points
    Hi Amanda,

    I think using LM25118 in this case would be a overkill as the output power is so low. It is more suitable using the boost regulator (with integrated FET). The webench suggested the LM25118 because of the low input voltage 3V, and usually the boost device has a max duty cycle limit to protect the FET.

    I don't know if the 3-22V input range can be relaxed. For 4-22V input range, it can use LM5000-3 boost regulator, here's the webench link: webench.ti.com/.../SDP.cgi . LM5000 has a 90% duty cycle limit, and 3.1V min Vin. So for 3Vin operation, the VIN pin needs to be externally biased (from Vout), and the output voltage will have some drop from 24V because the max duty cycle limit.

    If 3V in operation is a must, I'd suggest using a two-stage boost approach: adding front pre-boost only to cover the very low Vin condition. I think the TPS55340 can be add as the pre-boost, and LM5002 as the main boost. The efficiency will be lower, and larger size & cost. But still better than the LM25118 solution in my opinion.

    Best regards,
    Xiang