BQ25898: RBFET current direction

LIN SUN

Intellectual 620 points

Part Number: BQ25898

hello expert

please find RBFET on spec page14, thanks.

why current of this nmos flows "from source to drain"? I usually think it should be "from drain to source".

over 3 years ago

0 LIN SUN over 3 years ago

Intellectual 620 points

0 Ning T over 3 years ago in reply to LIN SUN

TI__Guru 54651 points

Hi,

The RBFET Q1 is to ensure the current will not go from PMID to VBUS when Q1 is off.

Thanks,

Ning.

0 LIN SUN over 3 years ago in reply to Ning T

Intellectual 620 points

Thanks Ning,

I know what you said when Q1 is off.

I'm asking "when Q1 is on, why current is flowing from VBUS(source) to PMID(drain)? I usually think NMOS current should "from drain to source".

0 Ning T over 3 years ago in reply to LIN SUN

TI__Guru 54651 points

Hi,

In buck (charge) mode, the current is flowing from VBUS to PMID because VBUS is the input. In boost (OTG) mode, the current is flowing from PMID to VBUS(source).

Thanks,

Ning.

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BQ25898: RBFET current direction