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Original question:

BQ77915: CHG and DSG MOSFETs are not turning on for stacking interface

BQ77915: BQ77915 EVM - How to Reset Overcurrent Fault Without Load Removal

Alex Mazur1
Prodigy 95 points
Part Number: BQ77915
Other Parts Discussed in Thread: BQ77905

Hello,

I have been having issues with trying to reset an over current fault with the BQ77915. Is removing the load the only possible way to reset the fault? This is not possible for our use case, so Ideally there would be another way to reset the fault. Connecting the battery charger is also not always possible for the product that this chip is being used for.

I tried using the BQ7791504, since that was recommended in a similar forum post to this one. I replaced the IC that was on the EVM with the BQ7791504. This ended up causing the overcurrent protection feature to not work at all, and I was able to draw a significant amount of current from my battery. This is not ideal, along with having the temperature sensing features disabled for the BQ7791504.

If removing the load is the only way to reset this fault, is there a similar TI chip that does not have this "feature"?

Regards,

Alex Mazur

  • 0
    TI__Expert 7455 points

    Hi Alex,

    Recovering from an overcurrent condition without load removal is an option we can program in the device in the factory. That is why the BQ7791504 does not require it. But, you are right, that particular version does not have overcurrent protection at all (see our device comparison table in the datasheet). If there is a business case, we can create a new version of the device with these features.

    We also have the BQ77905. It is a very similar device, but it does not have the OCC, cell balancing or HIBERNATE mode features of the BQ77915. There are more versions of this device available, but I'm afraid we do not have a version that does not require load removal to recover from overcurrent faults.

  • 0 in reply to Shawn Hinkle
    Prodigy 95 points

    Shawn,

    Thank you for the response. I also noticed that plugging the power adapter is the only way to reset faults, even after load removal. Is there a way to remove this feature as well?

    Regards,

    Alex Mazur

  • 0 in reply to Alex Mazur1
    TI__Expert 7455 points

    Hi Alex,

    Which faults are you referring to? The recovery options for the device is listed in Table 1 in the datasheet (page 12). None of the current faults should require adding a charger to the system.

  • 0 in reply to Shawn Hinkle
    Prodigy 95 points

    Shawn,

    The only way we are able to clear overcurrent faults on a stacked EVM is by plugging in the power adapter. Load removal does not clear the over current fault.

    Is TI able to review our schematic and layout? We have been struggling to get our design to work, and have seen different behaviors with the EVM than is stated in the datasheet. Any support with reviewing our design would be greatly appreciated. I can open another support ticket if needed, since this technically does not relate to the original question I posted.

    Regards,

    Alex Mazur

  • 0 in reply to Alex Mazur1
    TI__Expert 7455 points

    Hi Alex,

    That does seem strange. The device should recover with just load removal for OCD and SCD faults, and load detection for OCC faults. 

    We can definitely review your schematic. If you would like to send your information privately, you can send me a friend request and private message me.