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Original question:

TPS25946: External diode must be placed?

TPS25946: Is Diode between OUT and IN needed in rechargeable battery bidirectional load switch application?

Joey V.
Prodigy 70 points
Part Number: TPS25946
Other Parts Discussed in Thread: BQ2980

Tool/software:

I have a rechargeable battery load switch application where I plan to connect Single Cell Lithium (~4.2V, 2A Max) Battery to "TPS25946_IN" and BatteryCharger/PMIC to "TPS25946_OUT". There are certain scenarios where I want to powergate OFF this connection to do a subsystem power cycle.  

My understanding from the datasheet is the diode that connects between "TPS25946_OUT" and "TPS25946_IN" won't be needed since the Battery connected to "TPS25946_IN" will always provide voltage for TPS25946 to operate in a bidirectional current scenario (during battery charging).  In a fault scenario where battery voltage is 0 or disconnected and a charge current is applied from "TPS25946_OUT" I would exact no output on "TPS25946_IN". Is this correct?  

Are there any other ICs in TI's portfolio that you'd recommend this for application? 

Thanks.

  • 0
    Prodigy 70 points

    Looking through the datasheet again I noticed the quiescent current for the part is too high (~400uA) for my application. I'm targeting <25uA. 
    It looks like the BQ2980 with an external Common Drain Dual N-Channel FET may work for my application. Looks have ~5uA quiescent current. 
    Are there any other ICs in TI's portfolio that you'd recommend this for application that'd work within my low voltage and low quiescent current requirement? 

  • +1 in reply to Joey V.
    TI__Mastermind 39015 points

    Hi Joey,

    Your understanding is correct. You don't need diode since the input will always be higher than internal UVP threshold. Unfortunately, we don't have back-to-back FET low iq device in Power switch portfolio. If possible, can you raise another question with BQ part number. That will automatically get assigned to experts in that part and they can help you with it. 

    Best Regards,
    Arush

  • 0 in reply to Arush Gupta
    Prodigy 70 points

    Ok I will do that. 

    Just to wrap up this questions: In a fault scenario where battery voltage is 0 or disconnected and a charge current is applied from "TPS25946_OUT" I would expect no output on "TPS25946_IN". And it seems like the chip is fully specified to operate in this scenario. Is this correct?

  • +1 in reply to Joey V.
    TI__Mastermind 39015 points

    Hi Joey,

    Yes, the device blocks reverse current when it is off. This is an intended use case for this eFuse.

    Best Regards,
    Arush