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Lipo charger battery reverse polarity protection

UdiLevy
Prodigy 200 points
Other Parts Discussed in Thread: BQ24075

Hi all,

I am using a lipo charger BQ24075 on one of my boards, and I would like to add battery reverse polarity protection.

Can I use the configuration in the following application note:

slva139 by TI (i.e. FET protection)

Or would it cause any problems with the charger?

Thanks

Udi

  • 0
    TI__Mastermind 20220 points
    It should not cause problems with the charger. Just to note that 1 FET only will privide reverse protection in one direction of the current flow.
  • 0 in reply to Jing Zou
    Prodigy 200 points

    H,

    Thanks for your answer.

    Which direction will be protected if I connect the p-channel option exactly as in the application note- the battery supplying the circuit or visa versa?

    If so that means that the battery will not be protected from reverse voltage applied from the charger seeking the battery, am I correct?

    Can you suggest a better solution to protect both sides.

    Thanks in advance.

    Udi

  • 0 in reply to UdiLevy
    TI__Mastermind 20220 points

    Connection as shown in the application note will protect the battery from the reverse current from the load. You will need to connect a back-to-back NMOS to protect the load.

  • 0 in reply to Jing Zou
    Prodigy 200 points

    Hi Jing Zou,

    Thank you for answering my question, however I'm not sure I understand you completely. If I am not mistaking The original connection is designed to protect a circuit from battery reverse polarity, i.e. it should already cover the  "load protection" as it is. However I am not sure it protects the battery from reverse voltage applied by the charger (specifically the pulses that the charger generates when it searches for a battery to charge), is this correct?

    If so I am assuming the back-to-back FET should protect the battery from the charger pulses, can you please explain how this connection should be done.

    Thanks

    Udi

  • 0 in reply to UdiLevy
    TI__Mastermind 20220 points
    The original connection is designed to protect the battery from reverse current not the load as indicated in the title of the application note, "battery protection circuit". As shown in figure 3, you are protecting the battery by the body diode in the FET. You will need to connect a back to back NMOS where the body diode is in the opposite direction.