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TPS92691 is a LED controller, not a monolithic IC which has an integrated FET. Hence, I'm curious why the landing page for this part (https://www.ti.com/product/TPS92691) mentions that Iout(max) is 5A [note: this is a CC driver]. It was my understanding that the MOSFET is the one that dictated the max output current that could be used based on it's peak switching current which can be estimated based on the the input current required to be drawn from the battery / supply.

Are there any other criteria's to consider when estimating the max output current of a controller IC? I didn't even realize that controller ICs had max current ratings. Then again, I don't understand how voltage ratings are characterized by the controller as well - where do the input and output max and min's come about when the main components : mosfet, inductor, output cap, rsense need to designed and selected.

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  • \$\begingroup\$ Does the datasheet actually list a 5A max current? If not, they probably just put a recommended value into the parametric search fields so that it returns useful results. \$\endgroup\$
    – user1850479
    Commented Apr 23 at 2:47
  • \$\begingroup\$ No the datasheet doesn't mention anything about a max current limit. Ah, I see, that explains it. Anything else that could potentially limit max current in that controller though? Perhaps max voltage on sense pins or ... i really don't know, just throwing stuff out there. \$\endgroup\$
    – roaibrain
    Commented Apr 23 at 2:59

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It doesn't have a particularly strong gate driver and it has a fairly high switching frequency, so if you slap a really big MOSFET on there (with commensurately high gate charge) it will probably result in disappointing efficiency.

TI recommends a MOSFET with a low gate charge specification to limit the junction temperature rise and switch transition losses

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  • \$\begingroup\$ For the gate driver, an additional gate driver circuit such as LM5111 can be used to drive higher than the VCC of the converter. How does the high switching frequency influence this? \$\endgroup\$
    – roaibrain
    Commented Apr 23 at 4:04
  • \$\begingroup\$ That would be a good question to answer if you wanted to do that. I would assume “unfavorably” until proven otherwise. \$\endgroup\$
    – Spehro Pefhany
    Commented Apr 23 at 5:20
  • \$\begingroup\$ what do you mean? \$\endgroup\$
    – roaibrain
    Commented Apr 23 at 5:30

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