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BQ79616: Top-down CELL sequence

Ningguo CAI
Prodigy 90 points
Part Number: BQ79616

Tool/software:

Dear Experts,

The normal cell sequence is bottom up for sure. unfortunately, there is a need to have a top-down cell sequence in our applicaiton case.

you can find the diagram below for a 24S setup.

The CELL sequence is top-down from S2 to S1. I believe S2 is at a normal working condition.

S1 has multi-VC channels connected to CELL1-, which is the ground of battery pack. not only VSS, VC0, VC1, but also VC2, VC3, ..., VC8

Is it workable as normal? or any difference from the bottom-up sequence?

cheers

Alex

  • 0
    TI__Prodigy 500 points

    Hi Ningguo,

    The VCn/CBn (n>=3) should higher than 3V. I'm sure the S1 will have issues with accuracy.  I don't understand why VC1~VC8 of S1 should be connected to VSS. If VC8~V16 are connected to BAT, there will be no problem. I recommend using 12 channels per AFE.

  • 0 in reply to Harrison Yang
    Prodigy 90 points

    Harrison,

    The VCn/CBn (n>=3) should higher than 3V. I'm sure the S1 will have issues with accuracy

    if BQ79616 was powered externally, is there still an accuracy issue? 

    why VC1~VC8 of S1 should be connected to VSS

    so can I leave VC1-VC8 floating here? 

    If VC8~V16 are connected to BAT, there will be no problem

    You mean VC1-VC8 of S1 conencting to BAT? this will gurantee VC1-VC8 > 0V for sure, but in this case, VC9 to VC8 become a negative voltage, which is workable?

  • +1 in reply to Ningguo CAI
    TI__Prodigy 500 points

    Hi Ningguo

    HY：The VCn/CBn (n>=3) should higher than 3V. I'm sure the S1 will have issues with accuracy

    Ningguo: if BQ79616 was powered externally, is there still an accuracy issue? 

    HY: I think there is still bad accuracy. This is related to how the ADC is designed to handle common-mode voltage. Not the power supply voltage is too low.

    HY: why VC1~VC8 of S1 should be connected to VSS

    Ningguo: so can I leave VC1-VC8 floating here? 

    HY: No. VC1~ VC8 should be connected Cells. 

    HY: If VC8~V16 are connected to BAT, there will be no problem

    Ningguo: You mean VC1-VC8 of S1 conencting to BAT? this will gurantee VC1-VC8 > 0V for sure, but in this case, VC9 to VC8 become a negative voltage, which is workable?

    HY: I mean VC1~ VC8 connected to Cells. VC9~VC16 is unused channels. The datasheet gives two ways. The key is leaving upper channels as unused channels.

  • 0 in reply to Harrison Yang
    Prodigy 90 points

    Thank you very much, Harrison. it's clear now.