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Original question:

BQ25170J: Battery Charging/Protection Circuit with BQ25170J, BQ298215RUGR, BQ27427

BQ2982: Implementing the BQ2982 into an charging and fuel gauge circuit.

Lucas Lenarcic
Prodigy 30 points
Part Number: BQ2982
Other Parts Discussed in Thread: BQ27427, , BQ25170J

Hey, I've been designing a battery protection circuit with an additional charging and fuel gauge circuit. The circuits (Charging and fuel gauge) itself should work just fine. I was just wondering how both of them connect to the battery when i implement the BQ2982 protection IC. In the datasheet of the BQ25170J it says to connect the OUT (loading ping) directly to the battery plus pole. In the BQ27427 it says to connect the sensing pin (BAT) directly after the protection circuit. So my question now is, does the protection IC change anything? Is the Charging circuit still directly connected to the plus pole of the battery and the fuel gauge also directly connected after the protection IC, so "load" in my case. I've attached my circuits down below as well as a the reference circuits.

Thanks in advance,
Lucas

BQ2982:

Note: The first part is just a resettable fuse and a reverse polarity circuit.


BQ25170JDSGR (Charging IC):

BQ27427 (Fuel Gauge):

  • 0
    TI__Mastermind 35060 points

    Hello Lucas,

    The protection circuit typically connects directly at the battery side. So the charger would come after the protection IC, same with the gauge, as shown in its simplified schematic. The protection IC is the first line of protection for the battery. 

    I believe the fuel gauge and charger would be connected in parallel essentially. Both connected to the PACK+/PACK- of the BQ2982.

    Regarding your actual BQ2982 circuit. I am a bit concerned about the reverse-battery circuit. If the battery is connected backwards, the Q3 MOSFET will be OFF. However, current would still be able to flow through the body-diode of the FET. So if the cell is attached backwards, D5 and R27 would still have current flow and a voltage drop. This voltage is also likely what the BQ2982 would see, and I believe it could exceed the ABS min of the part. Unless I am missing something?

    Best Regards,

    Luis Hernandez Salomon