I'm designing a circuit based on the LTC4091 typical application:

Typical application

They use two Vishay SiS447DN P-Channel 20V MOSFETs. Unfortunately those parts are not in stock neither at Mouser nor DigiKey, so I'm looking into replacement parts. I'm not sure what to look for in a compatible MOSFET, besides the Vds = 20V.

I found this dual MOSFET chip : NVMD6P02 which shares some characteristics but Rds(ON), Id and Qd are off by at least an order of 10, so I'm not really sure it could be a good replacement.

If not, what would be a good replacement part, or more generally, what parameter to look for in an equivalent MOSFET ?

Edit : I'm currently designing the PCB so the package is not important as I can change it as long as I find a readily available equivalent part.

  • 1
    \$\begingroup\$ Normally Rdson should be same or less, Q same or less, VDS same or more. The most important thing is to select package such a way that you can always replace the MOSFET with something else. Which means both availability of alternatives and your soldering skill. And don't worry, it's just MOSFET, what can go wrong? \$\endgroup\$
    – user76844
    Jan 27 '19 at 19:32
  • \$\begingroup\$ Requests for recommendations of specific parts are off-topic for this site. VTC \$\endgroup\$ Jan 27 '19 at 19:34
  • \$\begingroup\$ @ElliotAlderson SE dupe bug. or double tap on mobile \$\endgroup\$ Jan 27 '19 at 19:55

The Vishay FETs are excellent parts with 1/4 RdsOn and 4x Ciss.

You may have to reduce Fsw by a factor of 3 to 4 to get same switching losses and thus same increase in L for the same impedance, considering the switching rate is in the range of < 1MHz with Turnoff delay rise from 50 to 150ns.


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