MOSFET for reverse current blocking with STEF01

[Central SUPPORT]

STEF01 has an interesting price but requires an external power MOSFET for reverse polarity protection. I see from the datasheet that ST has performed some measurements using external FETs, so which one would you recommend?

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[Central SUPPORT · Accepted solution]

When the application has a large output capacitor Cload, for example to power the protected circuit long enough for it to handle any required shutdown routines or to minimize the track inductance, it is recommended to implement the reverse current blocking MOSFET.

While we do not recommend any specific MOSFET, the main criterion for selecting the NMOS transistor is that it should be selected to operate within the range of the sourcing current and voltage of the Vg driver pin (30µA and Vout+10V, respectively).

In case a MOSFET with lower Vth is used, the voltage at Vg needs to be clamped to a suitable level with a clamping diode. Choosing a MOSFET with low RDSon ensures that the voltage drop, and thus power losses associated with the MOSFET, are low.