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Reverse current protection for series-parallel AA batteries

Abdelhakim ERRAOUI
Prodigy 80 points
Other Parts Discussed in Thread: LM66100, BQ77915

Hi,

I am designing a board supplied with 6 AA 1.5V batteries with the following configuration : 2 blocks of 3 series batteries in parallel, in order to get sufficient voltage level and double capacity.

The two blocks are not placed in the same side and that is why a standard reverse protection with a MOSFET will not work. In other words there is a risk that one of the blocks is inserted correctly and the other is not.

So, I want to have a solution that can protect the board in all cases :

  1. When the two blocks are wrongly inserted
  2. When only one block is correctly inserted

Current consumption is critical in my application. 90% of the time the circuit is in deep low power mode consuming approximately 10~20 µA.

Any help/suggestions please!

  • 0
    TI__Guru** 105760 points

    Hello,

    Is this only reverse polarity protection?

    I don't believe we have a solution that can detect those conditions, let me check with someone from our protectors team.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 80 points

    Hi,

    Yes actually it is an RPP.

    By searching a bit in your product selection in power management I found the LM74610 and LM66100 which I can use for my purpose. I think LM66100 is suitable for my application for its cost efficiency, minimal design and power consumption (quiescent current is less than 1µA in normal conditions).

    I can use it this way :

    But I'm not sure about two things

    One is the pulse/peak current that this switch can provide :

    I see in the datasheet page 4 in 6.1 section : Maximum Pulsed Switch Current (≤120 ms, 2% Duty Cycle) : 2.5A
    While, my board can have current bursts of 2A due to a cellular module in GPRS mode. The pulse width is 611µs every 4.46ms
    I don't know if this is critical for my application's current specs.

    The other is that Vin1 and Vin2 are typically the same :

    In normal operation, will the two LM66100 be ON or just one ? How the setup above can deal with two identical power levels ?

    Is there any other things I should take into consideration ?

    Would this solution work ?

    Thanks,

  • 0 in reply to Abdelhakim ERRAOUI
    TI__Guru** 105760 points

    Hello,

    I would recommend making a new post linking the parts you are thinking of using, since no part was linked your post was forwarded to the BGP group which deals with battery protectors, monitors, and gauges. These are the protectors we would specialize in: www.ti.com/.../products.html

    If you have some specific questions regarding the LM66100, when you make a new post with that part linked it will go to the team who specializes in that part.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 80 points

    Yes, I did it

    Thanks

  • 0 in reply to Abdelhakim ERRAOUI
    TI__Expert 7455 points

    Hi,

    For your case, I would recommend the BQ77915 battery protector.