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LTC4279 MOSFET selection

Question asked by jmbw on Jul 18, 2018
Latest reply on Jul 21, 2018 by jmbw

Is there any other MOSFET that can be used as the external switch with an LTC4279 PoE PSE controller?  The data sheet strongly pushes the Nexperia PSMN075-100MSE and PSMN040-100MSE as the only choices, and they're out of stock worldwide for 6 to 16 months, and the parameters that lead to these choices aren't explained.  I'd love to use something generic like an IRF540NS as the switch, if I could.  They're a little large but they're cheap and plentiful, have an even lower Rds(on) than the Nexperia parts, and seem like far more than enough to safely switch a Type 2 PoE load (half an amp), unless the PoE negotiation depends on very specific magic.  But the data sheet makes it very clear that I'm not qualified to choose.

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