LA-L191P missing +3VLP

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  • jasko_jacker
    Badcaps Legend
    • Oct 2014
    • 1140
    • italy
    #1

    LA-L191P missing +3VLP

    Hi, all
    LA-L191P BQ24781 signals pin 28 -> 19V [VCC], pin 5 -> 3.3V [ACOK] pin 6 [ACDET] 2.6V, pin 24 -> 5.3V [REGN], pin 25 -> 5.3V [BTST] ,
    missing +3VLP -> EC -> signals for manage BQ24781. In the power sequence the +3VLP is the first signal in AC mode.
    I presume that the bios is working because one time the motherboard generate +3VLP and goes ON but after a shutdown the situation
    came back to no power on -> no main 19V. The question is: who generates +3VLP which is the basis of all other signals?

    Every time with the BQ24780S it's like starting from scratch, is +3VLP essential for the BQ?

    Schematic & boardview - https://www.badcaps.net/forum/troubl...-g53g-la-l191p

    Many thanks
    Last edited by jasko_jacker; 09-16-2025, 01:55 PM.
    Tags: None
    • mon2
      Badcaps Legend
      • Dec 2019
      • 14521
      • Canada
      #2
      See attached. These 2 resistors enable the LDO rails.

      Click image for larger version Name: ldo_enabler.png Views: 28 Size: 15.5 KB ID: 3726523

        Comment

        • SMDFlea
          Super Moderator
          • Jan 2018
          • 21446
          • UK
          #3
          looks like PU301 .+19VB -> PR301 -> ENLDO_3V5V -> PU301,PU501
          All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

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