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LM3658 - protected against reverse cell connection?

Paul Schoenke
Expert 1375 points
Other Parts Discussed in Thread: LM3658

Hello!

Is the LM3658 Li Battery charger protected against a cell being connected backwards?

Any feedback or input is welcomed and appreciated!

Thanks again!

Paul

  • 0
    TI__Mastermind 22610 points

    Connecting a reversed battery to the LM3658 BATT pin will violate the ABS MAX rating for that pin.

    Not encouraged, as the device will most likely be permanently damaged.

  • 0 in reply to Donald Jones
    Expert 1375 points

    The device datasheet references reverse current protection. 

    Is there a recommended technique to protect against a battery getting connected backwards?

    You can’t use a diode since you need to charge and discharge the battery.

    Any feedback or input is welcomed and appreciated!

    Thanks again!

    Paul

     

  • 0 in reply to Paul Schoenke
    TI__Mastermind 22610 points

    Yes, the datasheet does reference 'reverse current protection', but that is limited to a corrrectly installed battery discharging back into the BATT pin of an un-powered LM3658.

    IBATT_PD  : Battery Leakage Current in Power Down Mode :  VBATT > (VCC + VOK_CHG )

    Not the same thing as applying a negative voltage to the LM3658 BATT pin.

    In this case the negative voltage will forward bias substrate diodes to the GND pin that will allow unlimited current to flow from the BATT pin to GND pin until either the bond wire is fused open or the IC metal traces are damaged. Inserting protection components, as you noted, will obstruct the charging path and/or offset the charging thresholds.

    There is no recommended technique to protect against negative voltage at the BATT pin.

  • 0 in reply to Donald Jones
    Expert 1375 points

    Thanks very much!  Does TI have a comparable solution with a different part that would have this feature along with the feature set of the LM3658?

  • 0 in reply to Paul Schoenke
    TI__Mastermind 22610 points

    Not that I can see. There might be something available, but it's not obvious.

    If anyone reading this thread knows of a part that would survive, hopefully they will post about it.