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A1278 820-2879. How is PPV42_G3H generated without charger?

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    #1

    A1278 820-2879. How is PPV42_G3H generated without charger?

    Hi, I am a beginner, can you help me to understand how is PPV42_G3H generated by the battery without when the charger is not inserted in this particular model? I can't see any direct connection between the battery and U6990 (which generates PPV42_G3H). From the schematic page "Power System Architecture" it would seem that there is continuity between PPVBAT_G3H_CONN and Q7085 but from the schematics and boardview there isn't. Also, from the page "Reverse-Current Protection" it says: "This node is powered through body diodes DCIN through Q7080, PBUS through Q7085 and Q7055". But from the same page there is no connection between that node and Q7055! I also checked with boardview
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    #2
    Re: A1278 820-2879. How is PPV42_G3H generated without charger?

    U6990 generates the 3v42 rail.

    The VIN of u6990 should have a dual diode with common cathode junction.

    This dual diode accepts power from the external power adapter or ppbus_g3h.

    When adapter is absent, ppbus_g3h will power this 3v42 rail which is now in battery mode.

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      #3
      Re: A1278 820-2879. How is PPV42_G3H generated without charger?

      Originally posted by mon2 View Post
      U6990 generates the 3v42 rail.

      The VIN of u6990 should have a dual diode with common cathode junction.

      This dual diode accepts power from the external power adapter or ppbus_g3h.

      When adapter is absent, ppbus_g3h will power this 3v42 rail which is now in battery mode.
      Please check the attachments. In this particular schematic there is no dual diode and no connection between ppbus_g3h and u6990

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        #4
        Re: A1278 820-2879. How is PPV42_G3H generated without charger?

        My bad..this logic board is different. The others will have a dual diode.

        For this case, follow the INTERNAL diodes inside of each mosfets between the battery and the VIN of u6990.

        Comment

          #5
          Re: A1278 820-2879. How is PPV42_G3H generated without charger?

          Originally posted by mon2 View Post
          My bad..this logic board is different. The others will have a dual diode.

          For this case, follow the INTERNAL diodes inside of each mosfets between the battery and the VIN of u6990.
          Perfect, thank you!

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