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TIDA-00817: Issues in the reference design extended to stacked up configuration

Shreya Agrawal
Prodigy 230 points

Part Number: TIDA-00817

I am working on a BMS design using BQ76PL455A-Q1 battery monitor and BQ34Z100 fuel gauge. The existing reference design of the single 16 cell monitor was extended in my use case for a 32s8p configuration. The design shows an excess current draw when the base battery monitor wakes-up receiving the pulse. I tried using a higher value resistance of 100ohm instead of 49.9ohm for the wakeup pin to debug the issue. Can you tell me if there are any changes to be done to the design tida-00817 when extended to stacked up designs, given that the entire circuitry works fine when only the battery monitors (not along with fuel gauge) are operated through a wakeup pulse.

  • 0
    TI__Intellectual 2710 points

    Hi Shreya,

    I will try to answer your question and help you debug your system.

    I looked at the TIDA-00817 design and didn't really noticed anything specific that needs to be done when stacking up this system for higher channel count.

    It seems like you are not using the EMB1428 devices in your system, am I correct?

    Where is this additional current coming from, is it on the WAKEUP pin?

    Keep in mind that when you stack two BQ76PL455 A devices the top stack ground is not a 0V potential but actually at the potential of the Cell-16 so you cannot tie both WAKEUP pins together, since one is referenced to GND and the other to CELL-16 voltage.

    Regards,

    Viktor.

  • 0 in reply to Viktor Tasevski
    Prodigy 230 points

    I am really sorry, the design I referred to was the TIDA-00717 reference design for passive balancing and not the one with active balancing. I am facing this issue in testing that design (extended to stacked up ICs) on hardware. 

  • 0 in reply to Shreya Agrawal
    TI__Intellectual 2710 points

    Hi Shreya,

    Ok, the same comment applies to this Reference design as well. You need to make sure that the WAKEUP pin voltage is referenced to the specific device Ground.

    Regards,

    Viktor.

  • 0 in reply to Viktor Tasevski
    Prodigy 230 points

    Okay I got that. I also wanted to ask if if have a maximum stack voltage of 270VDC (8p64s), what should the most efficient split up to be done for set of series cells if i want to use EMB1499 and EMB1428 for an active balancing design implementation?