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BQ7716: Use of BQ7716 and BQ29706 Together for UV and OV function

ROHAN KADAM
Prodigy 165 points
Part Number: BQ7716
Other Parts Discussed in Thread: BQ76922

Tool/software:

Hello All ,

I am searching for a simple passive charge-balancing IC for the 4S2P 26650 (3.3V, 2.6Ah) configuration which should start charge balancing routine on its own without any command from microcontroller .

BQ771612 has only OV functionality. is there any IC in the product portfolio which has UV ,OV and Output FET drive features ? if not then how to use BQ29706 and BQ7716 together to make use of UV function of  BQ29706

ic ?

Thanks 

  • 0
    TI__Mastermind 42060 points

    Hello Rohan,

    You could use the BQ76922 monitor/protector. This device has high-side N-FET drivers, OV/UV, current protections, and autonomous cell balancing.

    You can OTP this device with your custom settings and it will be able to operate without any MCU.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 165 points

    Thanks for the reply . After reading the datasheet, I have a few questions on device’s functionality.

    1. 

    Internal FETs have a minimum on-state resistance of 15 ohm. Thus, if 3.9V is chosen as the overvoltage threshold, the maximum balancing current is 260mA. Icell_dicharge_max is not present in the electrical specs.

    2.

    The device will only balance non adjacent cell at the same time in autonomous mode . does it mean in 4s configuration , 1-3 and 2-4 will be balanced with total maximum balancing current of 520mA ?

    3.

    The config register needs to be updated to reflect the non-use of the fifth cell on the IC if the 4s configuration is used. This helps  the IC in determining which cells are being used. Does OTP include this configuration register? Or does this data need to be reloaded into the configuration register each time the device is power cycled?

    This questionary has resulted  due to the fact that complete unavailability of microcontroller after factory production .

  • 0 in reply to ROHAN KADAM
    TI__Mastermind 42060 points

    Hello Rohan,

    ROHAN KADAM said:
    Internal FETs have a minimum on-state resistance of 15 ohm. Thus, if 3.9V is chosen as the overvoltage threshold, the maximum balancing current is 260mA. Icell_dicharge_max is not present in the electrical specs.

    The maximum balancing current you'd be able to do, would be ~50-mA or so. The minimum recommended resistance for the input resistors is 20-Ohms. So if you want higher balancing currents, you would require external balancing FETs. The Cell Balancing With BQ769x2 Battery Monitors application note is an useful document to read more about the balancing Slight smile.

    ROHAN KADAM said:
    The device will only balance non adjacent cell at the same time in autonomous mode . does it mean in 4s configuration , 1-3 and 2-4 will be balanced with total maximum balancing current of 520mA ?

    No, either cell 1/cell3 or Cell2/Cell4 will balance at one time. Each balance current would be applied to its respective cell.

    ROHAN KADAM said:
    The config register needs to be updated to reflect the non-use of the fifth cell on the IC if the 4s configuration is used. This helps  the IC in determining which cells are being used. Does OTP include this configuration register? Or does this data need to be reloaded into the configuration register each time the device is power cycled?

    All of the device's registers can be OTP'd, so this setting can be configured and OTP'd to the device. 

    Hope that helps!

    Best Regards,

    Luis Hernandez Salomon