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ADM1270 Issue

hi sir

I  want to design the ADM1270 in my system, but I have two issue need to clarity before layout

Q1.ADM1270 use the PMOS to be the switch, but PMOS cost Which expensive than NMOS, Why ADI use PMOS?

Q2.ADM1270 Have reverse protect by RPFG,But I can't find the RPFG vary which no matter passive voltage or negative voltage input

     can you help to clarity?

thanks

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  • Alex,

    the ADM1270 uses a PFET because it is easier to drive the gate. A device controlling an NFET would have to generate a floating gate drive circuitry to be able to turn on the NFET. This means the voltage on the gate would be >70V for a 60V application.

    RFPG is used to protect against reverse current through the sense resistor and not reverse voltage on the IC. The voltage on RFPG is 12V below Vcc when there is positive current flow, if the device detects negative current flow then the RFPG voltage goes to Vcc.

    Attached is a preliminary design tool you could use to start your design.

    Best Regards, LucaV

    attachments.zip
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  • Alex,

    the ADM1270 uses a PFET because it is easier to drive the gate. A device controlling an NFET would have to generate a floating gate drive circuitry to be able to turn on the NFET. This means the voltage on the gate would be >70V for a 60V application.

    RFPG is used to protect against reverse current through the sense resistor and not reverse voltage on the IC. The voltage on RFPG is 12V below Vcc when there is positive current flow, if the device detects negative current flow then the RFPG voltage goes to Vcc.

    Attached is a preliminary design tool you could use to start your design.

    Best Regards, LucaV

    attachments.zip
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