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BQ25125: Under voltage protection ??

James Sullivan73
Prodigy 205 points

Part Number: BQ25125

Tool/software:

Hello,

I have seen a failure where it seems that the BQ25125 discharged a battery below the threshold set in UVLO register.

I thought this part provides under-voltage protection - am I incorrect about this ?

.js.

  • 0
    TI__Mastermind 18945 points

    Hi James,

    Can you please clarify, you were still able to see voltage on SYS / PMID / LDO below the BUVLO threshold that was configured?

    Crossing the BUVLO threshold should result in the BATFET being disabled, though the device may still draw quiescent current.

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Prodigy 205 points

    Hello,

    I have x2 very dead batteries - that were discharged well below BUVLO.

    I am trying to track down the reason, so I wanted to confirm that the part disconnects from the battery.

    Also - what parameter specifies the quiescent current when disconnected?

    Is there any way I can be causing this by mis-configuration ?

    Thanks.

  • 0 in reply to James Sullivan73
    TI__Mastermind 18945 points

    Hi James,

    There is a few reasons for the behavior. 

    James Sullivan73 said:
    I have x2 very dead batteries - that were discharged well below BUVLO.

    What capacity are the batteries and how long did it take them to discharge to the current state from their last known state of charge?  Also, do you have a part number for the battery pack?

    James Sullivan73 said:
    I am trying to track down the reason, so I wanted to confirm that the part disconnects from the battery.

    The part should disconnect the System load from the battery so the load current should be reduced, but quiescent current and  battery self-discharge can still cause the battery to continue reducing charge at a much slower rate.

    James Sullivan73 said:
    Also - what parameter specifies the quiescent current when disconnected?

    I'm not certain that the datasheet specifies the quiescent current when the charger is shutdown. I believe the typical recommendation for this device is to set the BUVLO very low and to enter shipmode as the battery enters the lower limits of the battery voltage range. A typical value for Iq below BUVLO is about 1.3uA.

    James Sullivan73 said:
    Is there any way I can be causing this by mis-configuration ?

    It's possible that, if there is any other circuitry connected directly to the battery cell that these can cause the cell to discharge at a faster rate. If you have a schematic and a battery pack reference number I can take a look at any other possible causes for battery discharge.

    Best Regards,

    Juan Ospina