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TPS65982 N-FET choice

Oliver Schmutz
Prodigy 50 points
Other Parts Discussed in Thread: TPS65982, CSD17309Q3

Hi all,

On our design with TPS65982 we used an other N-FET than on the buster pack.

We used FDMC7660 from On Semiconductor.

Datasheet: www.fairchildsemi.com/.../FDMC7660.pdf

The schematic is nearly the same as on the booster pack.

If we power up our board we have around 2V on VBUS of TPS65982.

Because of this voltage not every USB device get detected from corntroller.

If we disconnect External Power VBUS Voltage drops down to 0 (no Device attached).

To verify our design we swapped to the FET used on booster pack.

==> CSD17309Q3


With this FET`s everything is fine. But why?

Is there a problem with the max gate capacity?

Br Oliver

  • 0
    TI__Mastermind 36751 points
    Hi Oliver,

    Make sure to check the orientation of the body diodes on the N-FETs, they should be pointing towards each other. This is the only thing that could potentially cause this issue.
    The gate charge is not really a concern, the only difference that would make is it would take a bit longer for the FET to switch.

    Thank you,
    Eric