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BQ25750: Recommendation for variable cell count

Dr. Alexander W. Lenhardt
Prodigy 130 points
Part Number: BQ25750
Other Parts Discussed in Thread: BQ25730, BQ25758

Tool/software:

Dear TI team.

Is there a recommendation for a schematic which allows a variable cell count for the BQ25750 device?

Something like in the BQ25730 would be great, where I can set the charging voltage via I2C.

I guess using an I2C-controlled resistor for the VFB controlling the charge voltage on BQ25750 will not give the required accuracy.

Any idea?

Thanks for your response in advance.

Best regards

Alexander W. Lenhardt

  • 0
    TI__Mastermind 31145 points

    Hello Alexander,

    I have a few suggestions for varying the battery charge voltage setting with I2C.

    1. With the BQ25750, you can use a digital potentiometer for the feedback resistor.

    2. You can also use the BQ25758 to charge batteries as well. The BQ25758 has constant voltage control and constant current control so it can charge batteries with a wide output range.

    Let me know if either of these suggestions would work.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Prodigy 130 points

    Hi Ethan.

    Thanks for the suggestions.

    I thought, the digital potentiometer for the feedback resistor does not give enough accuracy for the charge voltage.

    As for the BQ25758, I though about it, but I was looking for the auto-reverse feature which this part does not have.

    Please have a look for the explanation in my former post about the BQ25730 to understand what I am trying to do ;)

    But I guess I have a solution now, unfortunately I have to use a component not from TI (LTC7106).

    Best regards

    Alex

  • 0 in reply to Dr. Alexander W. Lenhardt
    TI__Mastermind 31145 points

    Hello Alex,

    A digital potentiometer will give a enough accuracy for the feedback voltage.

    The LTC7106 should work for setting the VFB voltage.

    Let me know if this is a workable solution to your system and let me know if you have any questions about this.

    Best Regards,
    Ethan Galloway

  • +1 in reply to Ethan Galloway
    Prodigy 130 points

    Thanks a lot.

    We will check it out and give a feedback if it works for us!

    Best regards

    Alex

  • 0 in reply to Ethan Galloway
    Prodigy 130 points

    Hi Ethan.

    We decided to stay with the BQ25730 first.

    After evaluating it's FRS mode, we guess that it can fit our needs better.

    Maybe we will see drawbacks with that solution later and have to come back to BQ25750.

    But actually it seems our design is doing what we are going to need.

    Thanks for your support at the moment.

    Best regards

    Alex