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BQ24610: Burned when battery plugged in

A M
Prodigy 10 points
Part Number: BQ24610
Other Parts Discussed in Thread: TVS2700

Hi,

There is a PCB with BQ24610, the schematics is like in the EVM. The BQ24610, a Schottky diode and a low-side MOSFET burned when I plug in a 6S LiIon battery, there is no AC adapter. Two of two prototype boards out. I have seen few threads here with the same or similar situation with no appropriate troubleshooting support for years. Could you guys really help? This IC looks like a real troublemaker to your reputation, and I consider to switch to LTC4013 from your friends at Linear Tech / Analog Devices.

  • 0
    TI__Mastermind 26990 points

    Hi,

    I have checked the threads with similar issue but most if not all are related to user application.

    What is your test setup when the damage occurred? 

    Can you provide the capture of VBAT voltage, inductor current, and PH voltage when this occurred?

    Can you provide the schematic and point out which Schottky diode is damaged?

    Also, can you provide the part number of the Schottky diode and the low-side MOSFET?

    Regards.

  • 0 in reply to Tommy Lin
    Prodigy 10 points

    Hi Tommy,

    Test setup: no AC adapter, no load, just a BQ24610 and a 6S battery (actual voltage 22V).

    Inductor current is unknown. Where should it flow from the battery thru the inductor?

    The schematics is the same as EVM, Schottky diode - ZLLS350TA, like in EVM.

    Low-side MOSFET is FDS8447, like in EVM.

    Now here are my thoughts:

    BQ24610 DS claims at Abs Max Ratings: PH max voltage is 36V and VCC is 33V. I suppose that there can be spikes of such or above magnitude at the moment the battery gets plugged in (especially if it is 5S-6S, brand new and fully charged). There is almost no room to find a protective TVS diode since it has to be 28V rated (to not get damaged while BATDRV open up a P-MOS, and voltage from the AC adapter will be at the BAT connector while the battery absent), and, in the same time, the TVS should suppress spikes at no more than 33V. Just check out TVS datasheets.

    LTC4013 rated at 60V at the pins of interest, and I guess, guys at LT/AD do know why.

    One more weak/suspicious place is the gate-source voltage of an N-MOS, driven from the HIDRV. The HIDRV ties the gate to GND, and when we connect the 22V charged battery, the gate-source voltage is -22V, that is above +-20V abs max rating of the most MOSFETs, including FDS8447 used in EVM. The P-MOS looks alive among the died neighbors mentioned above, but obviously it is not a good way to use components out of spec. If we would consider spikes the things get worse.

  • 0 in reply to A M
    TI__Mastermind 26990 points

    Hi,

    I tried to simulate the battery hot plug on EVM but I do not see spikes and no components are damaged.

    Have you tested your modification on the EVM?

    Can you provide the capture of VBAT voltage, inductor current, and PH voltage when this occurred?

    Regards.

  • 0 in reply to Tommy Lin
    Prodigy 10 points

    Hi Tommy! I have no modifications, my schematics is like in EVM.

    I sacrificed 3rd PCB with BQ24610 and captured VBAT voltage.

    https://photos.google.com/share/AF1QipMDCfNyxly2ZeRCvHUwNow1Jszvb2QyNAy6XDFxOdAfdksCJVE2B4q--QeYMBaXWQ?key=RW8yU0s3MkYzZmRfbTZkcmR2dXQwRWRzZnVLV1l3

    The BQ24610 cannot withstand real-life conditions even with the external protection.

  • 0 in reply to A M
    TI__Mastermind 26990 points

    Hi,

    The scope capture shows that the ringing exceed the the absolute maximum of the pins therefore damaging the chip.

    This ringing can be caused by multiple factor such as the battery wire length.

    You will need to add a voltage clamp (such as TVS diode) to clamp the ringing. You can check out the TVS2700 on ti.com.

    Regards.

  • 0 in reply to Tommy Lin
    Prodigy 10 points

    Hi Tommy,

    Okay, let's checkout TVS2700 together.

    According to the TVS2700 spec, its clamping voltage can be 33.9V max, that is above BQ24610 VCC max 33V.

    Moreover, TVS2700 rated voltage is 27V, but for 6S Li-Ion batteries there is a 27.6VDC adapter needed - they are widespread in the industry, and we need some margin for input voltage to get the buck converter inside BQ work properly.

    All that means this TVS will not work.

    I cannot use BQ24610 with the 6S Li-Ion battery and forced to look at other manufacturers.

    Tommy, thank you indeed for the conversation.

    Have a good day!

  • 0 in reply to A M
    TI__Mastermind 26990 points

    Hi,

    Thank you for the comments.

    There are other TVS diode (not limited TI products) you can find on website such as Digikey, last time I checked there are several TVS diode that fits the usage range and are in stock.

    Thank you for reaching out and have a good day.

    Regards.