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BQ25629: Permanently damaged BQ chips when loading battery via USB power bank

RK
Prodigy 50 points
Part Number: BQ25629


Hi there,


I have some questions regarding BQ25629 failure behaviour. We are using the BQ25629 in one of our projects. Unfortunately with are often destroying BQ chips while charging our battery (most of the time with higher current like 1,5A – 2A).

The behaviour of the damaged BQ Chip is mostly always the same and is the following:
Battery connected to the BQ, everything looks fine, no fault flags and sys voltage is provided and stable. As soon as we plug in USB supply (from a powerbank) the BQ Chip shuts down Sys voltage and it seems that BQ is going into shutdown/Reset and the chip is permanently damaged. This happens within 1 to 2 seconds.

Once destroyed the BQ chip can still operate on Battery (I2C communication and sensor values work properly) but when plug in USB supply, the chip keeps shuting down SYS-Voltage and restarts permanently (probably because TDI is rising above 120°C). Only solution is to replace the chip which makes the board working again.

We have manually added the missing PMID capacitors of 10uF and 0.1uF (see schematics attached) and placed the VBUS capacitor closer to the chip, which makes it more difficult to destroy the BQ chip, but we still had some cases, when the chip got destroyed.

So our questions are:
- Do you know the behaviour of a damaged BQ Chip described above and is it related maybe to a specific problem ?
- What do you think can cause these problems? 

Thanks for your help!

Kind Regards,
Lukas

bq-schmatics.pdf

  • 0
    TI__Guru 59141 points

    Lukas,

    We will check and get back to you this week.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    TI__Guru 59141 points

    Hi Lukas,

    1, Similar behavior was not reported in the past.

    2. Please follow Figure 10-2. BQ25629 Application Diagram and the EVM schematic on the User's guide especially for the caps at the charger pins.

    1) REGN needs 4.7uF cap.

    2) A 1uF cap needs to be placed close to the VBUS pin.

    3) Is C16 (220uF) close to the SYS pin of the charger? If yes, please remove C16 and try again. 

    3. Please make sure to follow the guidelines in 12 Layout on the d/s.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Prodigy 50 points

    Hi Ning,

    thank you for your answer.

    We will follow your advices and improve our layout in our next revision. If this still does not solve our problem we will come back to you for further help.

    Thanks and regards,
    Lukas