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Original question:

BQ25306: BQ25306RTER

BQ25306: BQ25306RTER

FirazAhmed Peerjade
Prodigy 10 points
Part Number: BQ25306

Tool/software:

Hello,
I am using the BQ25306RTER for a charging circuit, and I’ve attached my schematics for reference. Initially, I designed this circuit for a 3.8V output at 2A current, and it is working fine. However, now I am trying to switch the output from 3.8V to 8.4V. The voltage is not changing even after replacing the FB resistor (R11 with 1.33MΩ).

  • 0
    TI__Mastermind 32010 points

    Hello, 

    Thank you for reaching out via E2E. 

    Switching R11 to 1.33MΩ in your design is the correct resistance value to set full charge voltage to approx. 8.4V. R1 = 1..33MΩ and R2 = 200kΩ will set VBATREG to 8.41 using the equation from table 7-1 Pin Functions in the BQ25306 datasheet. 

    FirazAhmed Peerjade said:
    The voltage is not changing even after replacing the FB resistor (R11 with 1.33MΩ).

    You mention the voltage is not changing, but please understand the BQ25306 device charges battery in constant current mode then constant voltage mode. This is shown in Figure 9-1 of the datasheet. Once FB resistor is changed if battery voltage is still at 3.8V the device will be in precharge phase of charge cycle. 

    Do you have two series batteries connected in your testing after changing the FB resistor? 

    Best Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    Prodigy 10 points

    Yes, two batteries connected in series, and my battery voltage is around 6.9V. 

  • 0 in reply to FirazAhmed Peerjade
    TI__Mastermind 32010 points

    Hello, 

    Thank you for your reply. 

    Given the battery voltage is around 6.9V what charge current do you observe? Is it the 2A you expect to see based on resistor value at ICHG pin connection? 

    Best Regards,

    Garrett