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BQ76952EVM: Does not pass Quick Start tests

Scott Sewell
Prodigy 10 points
Part Number: BQ76952EVM
Other Parts Discussed in Thread: BQSTUDIO

Our new Battery Management Studio EVM won't pass Quick Start.

It starts up with the EVM connected and can communicate with the device (7695_0_36). Initially the pack voltage (23mV) is dramatically lower than the stack (4781mV). Both DSG_FET and CHG_FET are on. The CUV bit is set. OTOH when I click on FET_ENABLE the pack voltage goes up (5083mV) and DSG_FET goes off. When I drop the supply voltage from 48V to 38V nothing changes.

What's up?

  • 0
    TI__Mastermind 38350 points

    Hello Scott,

    Can you share your bqStudio window and how you are connecting everything to the board? The voltages here are not making too much sense to me. 

    Do you have the resistor ladder populated? What voltage is being applied vs, what is being read (a BqStudio capture here would be good).

    VC16 is used for the PACK measurements, so if this is not connected, there could also be problems.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 10 points

    Hi Luis,

    Actually, John here, Scott's tech. Thanks for your reply. Here's the screenshot:

    The resistor ladder is fully populated by shunts as I don't have a battery connected yet until I know the EVM is working. 48V applied, though not at the moment. 

    Regards,

    John

  • 0 in reply to Scott Sewell
    TI__Mastermind 38350 points

    Hello John/Scott,

    In this case, I see that you have around ~595-mV per cell. 595*16 = ~9.52-V battery stack voltage. I see that the Stack voltage reads 949-userV. By default userV is cV, so 949-userV would be equal to 949-cV, or 9.49-V, so it seems like this is accurately being measured. DSG seems to be ON in this case.

    I am a bit confused as to what is the problem here? Do you mind explaining it in a bit more detail. Sorry about that!

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 10 points

    Hello Luis,

    My concern was that the EVM didn't pass the Quick Start tests so I noted how the results differed and send them along. If it's indeed working properly I'll proceed from there. Thank you very much for your help.

    Regards,
    John