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BQ76925: Using external balance FETs

József Hermann
Expert 1040 points
Part Number: BQ76925
Other Parts Discussed in Thread: BQ77915

Dear All,

after '77915 (works fine) I would like to try the '76925 too.

Can I use external MOSFETs to extend balance current similarly to the '77915? Whether the internal FETs are P or N channel types?

Thanks,

Joseph

  • 0
    TI__Guru 54715 points

    Hi Joseph,

    Yes, you can use the same technique for external balancing with the BQ76925 as you did with the BQ77915.  Both parts are designed for relatively high current balancing so the same FET and external circuit should work fine.  The internal balance FETs on the BQ76925 are likely a mix of N and P channel so that the control voltage is within the power supply range of the part.  You may have noticed the description of the charge pump in the BQ77915 data sheet to operate the internal N-channel balance FETs, the BQ76925 does not use that method.  The effect on the IC pins is the same, you can use either N or P channel FETs externally.  

    Remember that the BQ76925 is host controlled, your host will need to decide which cells to balance when. This gives you more flexibility but is more work.  Remember to consider the cell input pin voltages and power in the part during balance control.