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  1. #1
    Junior Member level 3
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    Cluj, Romania
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    Need help identifying SOT23-6 with marking code B984 (boost circuit controller)

    Photos attached.

    This is a second forum where I post the same exact question, hoping to get an answer...

    This is part of the case circuitry of a bluetooth earphone set.
    Unfortunately the case no longer charges the earpieces, see video: https://www.mediafire.com/folder/n4n...+charging+case

    The main part I am interested in is the B98̅4 (tried to put the combing overline only over 8, ain`t working that good):
    Click image for larger version. 

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    I managed to find many many sot23-6 components (boost / step-up converters suitable for battery operation - e.g. very low quiescent current) but unfortunately none matches the pinout on the board...

    I would also be interested to find the other parts on the board, it seems that there is no more led display of the case battery, although it does charge its 902030 (size) lithium battery when I connect the microusb. The led display is surely controlled by the (ST Micro) STC 15w404as cpu which might also be dead (but I don`t really care about it).
    Click image for larger version. 

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    The 57b4 might be some version of tp4057 but I`m not sure what the YJ32 SOT23-5 is....

    I had attached pictures with the entire circuit and closeups with all the parts in detail.

    Thank you in advance!

    Photos of entire board follow:
    Click image for larger version. 

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ID:	151786Click image for larger version. 

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    Additional animation that I made the best I could with front/back of the board:
    Click image for larger version. 

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    Last edited by KlausST; 15th March 2019 at 11:07. Reason: improved "overligned 8"

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  2. #2
    Advanced Member level 1
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    Aug 2016
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    Re: Need help identifying SOT23-6 with marking code B984 (boost circuit controller)

    That SOT-23-6 next to the inductor appears to be an MT3806.

    The MT3806 application note details an SK34 schottky as does your image and has pin 6 as NC you can do simple continuity testing you can also check the switching frequency at the inductor which should be as high as 1.2Mhz to determine if its the chip.

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