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TIDA-010030: Question about BQ76940 in reference design

jediengineer
Prodigy 165 points

Part Number: TIDA-010030
Other Parts Discussed in Thread: BQ76940,

I noticed in the reference design, the several of the NC pins (11, 12, 16, 17) on the BQ76940 were being used. Can you explain their function, how to interface to them in code, and why you used them?

  • 0
    TI__Expert 3356 points

    Hi, 

    The NC Pins connections guidance is on datasheet: 7.4.1 bq76940 Pin Map. Please follow that.

    Please click "This resolved my issue" if no more questions. Thanks.

    Best Regards,

    Ryan Tan

  • 0 in reply to Ryan Tan
    Prodigy 165 points

    I see. It only says "short to CAPx" - you have them capacitively coupled to C5x and C10x - which is ORed with C9 and Cell9 - why? Just trying to wrap my head about the design... 

  • +1 in reply to jediengineer
    TI__Expert 3356 points

    Hi,

    CAPX need to connect to C5X and C10X with capacitors, this is also claimed in datasheet Pin map table. For TIDA-010030, C9/Cell9 is actually measured by VC10 since TIDA-010030 is a 13s solution, the way to configure BQ76940 for different cell count is in datasheet table 8-3. I followed EVM design to connect C9, Cell9 and VC10X.

    Please click "This resolved my issue" if no more questions. Thanks.

    Best Regards,

    Ryan Tan

  • 0 in reply to Ryan Tan
    Prodigy 165 points

    Ok, I think I see what you did - referring p5 of SLUA749A, I put my diodes as drawn, but I completely missed the caps to the Capx pins. I referred to that table for my design - 12s - which is essentially the same as your 13s, except I have to short cells 4 and 5. So it shouldn't be much different aside from your design.