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CSD25501F3: Can I use TI P-MOSFET in series to get a larger effective VDS?

RJ Hopper
Mastermind 18095 points
Part Number: CSD25501F3

Greetings:

I am considering using the p-MOSFET as a load switch to turn-on/off a -28V to a GaN switch.  TI's portfolio of p-MOSFETs "min-out" at -20V.  Can I put two p-MOSFETs in series to effectively reduce the VDS on each individual device?  Note, the current draw for the application is next-to-nothing.

Generally, this technique is not recommended because there is a chance one device turns on first (VEE side) and the other device (load side) will see the full -28V momentarily.  The gates will be tied together to ensure synchronous operation.  I can add a small RC time constant circuit to the gate of the VEE drain side so that device will definitively turn on last. 

Is this type of technique viable?

--Russell

  • 0
    TI__Mastermind 35380 points

    Hello Russell,

    Thanks for the inquiry. In theory, series connection of MOSFETs is possible to achieve higher effective breakdown voltage. However, due to parametric differences between devices it is generally not recommended. Variations in threshold voltage means one FET is always going to turn on before the other and turn off after the other device and there is no way to ensure that the breakdown voltage will not be exceeded. Just to be safe, I would recommend selecting a P-channel device with adequate breakdown voltage rather than operating two devices in series.

    Best Regards,

    John Wallace

    TI FET Applications