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

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  • xjimx
    New Member
    • Aug 2022
    • 4
    • Italy
    #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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    • mon2
      Badcaps Legend
      • Dec 2019
      • 14011
      • Canada
      #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.

        Comment

        • xjimx
          New Member
          • Aug 2022
          • 4
          • Italy
          #3
          Re: A1278 820-2879. How is PPV42_G3H generated without charger?

          Originally posted by mon2
          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

            Comment

            • mon2
              Badcaps Legend
              • Dec 2019
              • 14011
              • Canada
              #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

                • xjimx
                  New Member
                  • Aug 2022
                  • 4
                  • Italy
                  #5
                  Re: A1278 820-2879. How is PPV42_G3H generated without charger?

                  Originally posted by mon2
                  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!

                    Comment

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