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BQ24296: BQ24296 - Whining inductor - low switching frequency

Mohsen S
Prodigy 40 points
Part Number: BQ24296
Other Parts Discussed in Thread: BQ25622

Tool/software:

Hi there,

I am using BQ24296MRGER in my design, and the switching on inductor while charging the battery (while device is off) What are the possible solutions? The switching is happening at 1.5MHz


Thanks

  • 0
    TI__Mastermind 31810 points

    Hi Mohsen, 

    Thank you for reaching out via E2E. Firstly the standard 1.5MHz switching frequency of the BQ24296 is outside the audio frequency range. When there is sufficient output current draw between battery charging and SYS load regulation I would not expect you to encounter audible noise. 

    Your description that the behavior occurs when the device is off while charging the battery leads me to believe you may have this inductor whining due to PFM mode operation where the switching frequency is reduced in order to improve light load efficiency.

    TI has some newer switching charger ICs, such as BQ25622, where PFM operation can be disabled, but unfortunately this feature is not available on the BQ24296. 

    Different types of inductors may whine more than others so one possible solution would be to try a different inductor than you are currently using. Also please be aware the noise could be coming from an output capacitor rather than the inductor. 

    Best Regards,

    Garrett