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Lenovo YOGA 3 Pro 1370 +3VALW Missing Board NM-A321

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    Lenovo YOGA 3 Pro 1370 +3VALW Missing Board NM-A321

    Laptop: Lenovo YOGA 3 Pro-1370
    Board: NM-A321
    Schematics attached, Page: 30
Question: The BQ24770 is a Battery charger IC. It's pin #5. I'm not getting ACOK signal. ACOK signal will generate +3VALW on power which is missing.
    
As per BQ24770, datasheet attached, Pin #5. For this to be on the following criteria needs to be met:
ACDET above 2.4 V: This is correct and board is good with this value.

    VCC above UVLO but below ACOV: This is what I'm unsure about, where do I find UVLO? It's not on schematics, from Googling it means, undervoltage lockout (UVLO) function to disable the device at low supply voltages. From this I gather it's the ENABLE signal needs to be ENABLE, but I don't know where this is and how can I find It on schematics.

    VCC above BAT: This is also correct, when there is no Battery is present, it's 0V, I gather this should be OK unless I'm wrong.
    
Can someone please help me understand the UVLO and how I can measure it?

    I have also used 2 original Lenovo chargers, 1 compatible and for the original Lenovo chargers, their cables are removable, 3 cables altogether I've tried.

    All had 20V supplied to the system. Battery would not charge as well and the issue is same with or without battery plugged in.

    Thank You!

    [MOD EDIT} Link to schematic & Boardview -> https://www.badcaps.net/forum/troubl...0-lcfc-nm-a321
    Attached Files
    Last edited by sikocan; 04-14-2021, 07:08 AM.

    #2
    Re: Lenovo YOGA 3 Pro 1370 +3VALW Missing Board NM-A321

    Are you getting +3VALW on the other end of PR64??

    Comment


      #3
      Re: Lenovo YOGA 3 Pro 1370 +3VALW Missing Board NM-A321

      No, the same very low I believe it was 0.2v or so, the resistor measures 96k ohms

      Comment


        #4
        Re: Lenovo YOGA 3 Pro 1370 +3VALW Missing Board NM-A321

        Your problem is not charging ic as acok# will be pulled from +3VALW and since +3VALW is not available, there is no question of getting ACOK#. You need to probe your 3/5V regulator IC.

        Comment

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