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Original question:

BQ25798: Please help me to select a suitable Buck-boost mode BMS IC and Fuel gauge.

BQ25798: Help in selecting the compatible fuel gauge according to the application.

Vaidehi Satfale
Prodigy 20 points
Part Number: BQ25798
Other Parts Discussed in Thread: BQ34110

Tool/software:

Hello,
I am working on a design where battery usage is the primary operating mode, and therefore charging is required whenever an adapter is connected. For this, I am considering the following combination of devices:

  • BQ25798 → to handle charging and power-path management.

  • BQ34110 → as a system-side fuel gauge 

  • Battery pack → 2S2P Li-ion (~8.4 V nominal).


So, is this combination (BQ25798 + BQ34110) suitable for a battery-centric system where accurate monitoring of battery status is critical? Or what would you recommend for the same.
Thanks and Regards

  • +1
    TI__Guru**** 167196 points

    Hi Vaidehi,

    What it the max system load, input source voltage and current and desired charge current?  

    Regards,
    Jeff

  • 0 in reply to Jeff F
    Prodigy 20 points

    • Max system load: 5 V / 3 A (15 W).

    • Input source voltage: 12 V adapter.

    • Desired charge current: 4.5 A (0.5C for 9 Ah pack)

  • 0 in reply to Vaidehi Satfale
    TI__Guru**** 167196 points

    Hi Vaidehi,

    The SYS output of the charger has a minimum value of MINSYS (7.2V for 2S battery pack) and then follows the battery voltage up to regulation (8.4V default for 2S battery pack).  You will need a dc/dc converter following SYS to provide the 5V/3A load.  Also, if you need to simultaneously provide the 15W system load plus the 4.5A*8.4V = 37.8W charge current for a total of 52.8W output, the BQ25798 cannot provide from a 12V adapter.  The BQ25798 input current is limited to 3.3A which is 12V*3.3A = 39.6W <<52.8W.  Is the 15W system load an infrequent peak load transient that battery can help supplement?

    Regards,

    Jeff