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BQ76920: Difference between BAT- and PACK-

Zachary Pratt
Prodigy 10 points
Part Number: BQ76920
Other Parts Discussed in Thread: BQ24753A

I am planning on using the bq76920 balancing IC (top) with the bq24753a charging IC (bottom). I am confused with the difference between PACK- and BAT-. The bq76920 design reference shows them as two separate points. Any help would be greatly appreciated. Thanks.

  • 0
    TI__Expert 4640 points
    Hi Zachary,

    Pack minus refers to the connection to the system you will be powering on. Same goes for when you will want to charge the battery pack. The Bat minus refers to the negative terminal of your battery cells. The bq76920 is part of the battery system that together with the battery cells will be your 2 terminal battery (Pack + and Pack -).

    hope this clears it up for you.

    Thanks.
  • 0
    TI__Expert 6085 points
    Its also to be noted, the BAT-/Pack- path is a high current path ( when both DSG & CHG are ON). In the layout,the system GND should connect @ SRP.
    All of the device GNDs( VSS, decoupling cap GND) can connect via "net tie) to the SRP point. This is detailed on the d/s on page 51.
  • 0 in reply to Miguel Angel Rios
    Prodigy 70 points

    I am also confused with PACK- and BAT-. The BAT- is connected to GND in the bq76920 circuit. In the bq2453a circuit, there are GND and PACK-. If we connect the GND of bq76920 to the GND of bq2453a, and the PACK- of bq76920 to the PACK- of bq24530, however in bq2453a circuit the PACK- is connected to GND so that means PACK- is equivalent to BAT-?

    I think the above explain is wrong. The GND of battery pack (bq76920 circuit) cannot be connected to the GND of battery charger (bq2453a circuit). Actually the PACK- in bq76920 circuit is the GND of battery charger (bq2453a circuit). Right?

  • 0 in reply to oulutek
    TI__Expert 4640 points

    Hi,

    You are correct. The BAT - is the GND for the battery pack and the ground of the bq76920. For the Charger the PACK - is the ground.

    THanks

    Miguel

  • 0 in reply to Miguel Angel Rios
    Prodigy 70 points

    Then how about using a MCU to control the bq76920? Should we connect the GND of MCU to PACK1 of bq76920?

    Meanwhile, the MCU has to process other signals not related to bq76920. Such as the MCU has to measure the voltage of the adapter voltage which is used to charge the battery.

  • 0 in reply to oulutek
    TI__Expert 4640 points
    Everything inside the pack should reference the BAT-. Everythign outside the pack references the closest ground which is Pack -.