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bq76920: bq76930, bq76940 external balance resistor size

WM5295
Guru 54715 points
Part Number: BQ76920

Hi,

Regarding the application report bq769x0 Family Top 10 Design Considerations, could you tell me if I can use a small resistance for the balancing circuit, for high discharge currents, when using external balancing MOSFETs? The documentation gave the impression that you can't, which doesn't quite make sense when using external balancing FETs.

  • 0
    TI__Guru 54715 points

    Hi,

    Yes, a small resistance can be used with the external balance circuit, Rbal in figures 5, 6, 7, and 8.  Of course be sure that the interconnect can support the current, the resistor & board can dissipate the power, and the FET can support the current at the available Vgs. Also keep in mind the common path resistance at the group boundary as shown in figure 8.  If wires are used it may be desirable to use a heavier wire or separate connections from the board back to the cells to avoid measurement errors from the common path resistance.