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BQ77915: Questions about IC

Michael M1
Prodigy 140 points
Part Number: BQ77915

Hello, I have been working on putting this board together for the last month or so and I just have a few last questions I was not able to find in the gigantic datasheet :)

1. What is the minimum difference between cells to start balancing?

2. I don't understand what load removal detection is and what it is for /when would you enable it or disable it?

3. I noticed some faults don't clear by themselves and require the battery to be removed and reconnected to clear the fault and restart the chip. 

a) which faults does this apply to?

b). can you connect a charger to the board to clear the fault instead of removing the battery?

c) is there anyway to not need manual intervention to clear the fault? If not, is there an appropriate spot to put a reset button? (So the end user in a closed system does not have to open the device)

Thanks for answering my questions! I spent a lot of time in the datasheet and was not clear about these 3 things.

  • 0
    TI__Prodigy 590 points

    Hello Michael,

    Our AE expert will answer your questions when back to office.

    Thank you

  • 0
    TI__Guru* 81034 points

    Hi Michael,

    Please see the answers to your questions below:

    1. What is the minimum difference between cells to start balancing? Cell balancing is tricky to fully understand, so I made this video to help explain when the cells start and stop balancing in detail. Hopefully this helps make things more clear: https://training.ti.com/how-cell-balancing-feature-works-bq77915 

    2. I don't understand what load removal detection is and what it is for /when would you enable it or disable it? Load removal detection is an important basic feature for many battery packs. Without a load removal detection circuit, the battery system has to turn on the FET very briefly to see if the short persists, or simply never recover until a charger is detected. For and under-voltage fault, you want to prevent the part from toggling in and out of protection as the cell voltages recover after the loss of the load, at least for the first several cycles

    3. I noticed some faults don't clear by themselves and require the battery to be removed and reconnected to clear the fault and restart the chip. Are you referring to load removal? If you do not desire this feature, pulling LD to VSS will force the device to always detect the load is removed.

    a) which faults does this apply to? Faults associated with discharge - OCD, SCD, UV.

    b). can you connect a charger to the board to clear the fault instead of removing the battery? I do not think this is sufficient.

    c) is there anyway to not need manual intervention to clear the fault? If not, is there an appropriate spot to put a reset button? (So the end user in a closed system does not have to open the device) There is no reset pin for this device, so a reset button is not possible.

    Best regards,

    Matt